Head and Neuroanatomy (THIEME Atlas of Anatomy)

THIE ME Atlas of Anatomy Head and Neuroanatom y

Michael Schuenke Erik Schulte Udo Schumacher Consulting t ctitors

Lawrence M. Ross Edward D. Lamperti Etha n Taub lllustr.u ions l>y

Markus Voll KariWesker

I

Thieme

Head and Neuroanatomy

THIEME Atlas of Anatomy Consulting Editors

Lawrence M. Ross, M.D., Ph.D., Department of Neurobiology and Anatomy University of Texas Medical School at Houston

Edward D. Lamperti, Ph.D., Immune Disease Institute and Harvard Medical School

Ethan Taub, M.D. Neurosurgery Department University Hospital, Basel

Authors

Michael Schuenke, M.D., Ph.D., Institute of Anatomy Christian Albrecht University Kiel

Erik Schulte, M.D., Department of Anatomy and Cell Biology johannes Gutenberg University

Udo Schumacher, M.D., FRCPath, CBiol, FIBiol, DSc, Institute of Anatomy II: Experimental Morphology Center for Experimental Medicine University Medical Center Hamburg-Eppendorf

In collaboration with Juergen Rude Illustrations by

MarkusVoll KariWesker 1182 Illustrations 72 Tables

Thieme Stuttgart · New York

l.ibraryofCongress CDIXlloging-in-Publication Dam is available from the publisher.

This book is an authorized and revised translation of the German edition published and copyrighted 2006 by Georg Thieme Verlag, Stuttgart, Germany. Title of the German edition: Schuenke et al.: Kopf und Neuroanatomie: Prometheus Lernatlas der Anatomie.

Illustrators Markus Voll, Fiirstenfeldbruck, Germany; Karl Wesker, Berlin, Germany (homepage: www.karlwesker.de) Translator TerryTelger, Fort Worth, Texas, USA

Important note: Medicine is an ever-changing science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowleclge at the time of production of the book. Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user Is requested to Hilmlne carefully the manufacturer's leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule oreveryform of application used is entirely at the user's own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page.

C corrected reprint 2010

Georg Thieme Verlag Riidigerstra8e 14 D-70469 Stuttgart Germany http:ffwww.thleme.de Thieme New York, 333 Seventh Avenue, New York, NY 10001, USA http:ffwww.thleme.com Typesetting byweyhlng digital, Ostflldern-Kemnat Printed In China by Everbest Printing Ltd, HongKong

Plus Version -Includes online access to WlnklngSkull.com PWS

Softcover

ISBN 978-1-60406-290-8 Handcover ISBN 978-1 -60406-296-0

Some of the product names, patents, and registered designs referred to In this book are In fact registered trademarks or proprietary names even though specific reference to this fact Is not always made In the text. Therefore, the appearance of a name without designation as proprietary Is not to be construed as a representation by the publisher that It Is In the public domain. This book, Including all parts thereof, Is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, Is Illegal and liable to prosecution. This applies In particular to photostat reproduction, copying, mimeographing, preparation of microfilms, and electronic data processing and storage.

1234S6

Foreword

Preface

Our enthusiasm for tile THIEME Atlas of Anatomy began when each of us, Independently, saw preliminary material from thlsAtlas. We were Immediately captivated by the new approach, the conceptual organization, and by tile stunning quality and detail of the images of the Atlas. We were delighted when the editors at Thieme offered us the appertunlty to cooperate with them In making this outstanding resource available to our students and colleagues In North America.

As it started planning this Atlas, the publisher sought aut the opinions and needs of students and lecturers In both the United States and Europe. The goal was to find out what the "ideal" atlas of anatomy should be-ideal far students wanting to learn from the atlas, master the extensive amounts of Information while on a busy class schedule, and, In the process, acquire sound, up-to-date knowledge. The result of this work Is this Atlas. The THIEME Atlas of Anatomy, unlike mast other atlases, Is a comprehensive educational tool that combines illustrations with explanatory text and summarizing tables, Introducing clinical applications throughout, and presenting anatomical concepts In a step-by-step sequence that allows for the Integration of both systemby-system and topographical views.

As consulting editors we were asked to review, for accuracy, tile English edition of the THIEME Atlas of Anatomy. Our work Involved a conversion of nomenclature to terms In common usage and some organizational changes to reflect pedagogical approaches in anatomy programs In North America. In all of this, we have tried diligently to remain faithful to the Intentions and Insights of the original authors. We would like to thank the team at Thieme Medical Publishers who worked with us. Heartfelt thanks go firtst to Kelly Wright, Developmental Editor, and Cathrin E. Schulz, M.D., Executive Editor, for her assistance and checking and correcting our work and for their constant encouragement and availability. We are also grateful to Bridget Queenan, Developmental Editor, who provided a uniquely thorough, thoughtful, and cooperatiVI! approach from tile moment she entered the process in the editing of this volume. We would also like to extend our heartfelt thanks to Stefanie Langner, Production Manager, for preparing this volume with care and speed. lawrence M. Ross, Edward D. lamperti EthanTaub

Since tile THIEME Atlas of Anatomy Is based on a fresh approach to the underlying subject matter itself, it was necessary to create for it an entirely new set of illustration5-il task that took eight years. Our goal was to provide illustrations that would compellingly demonstrate anatomical relations and concepts, revealing the underlying simplicity of the logic and order of human anatomy without sacrificing detail or aesthetics. With the THIEME Atlas of Anatomy, it was our intention to create an atlas tllat would guide students in their initial study of anatomy, stimulate their enthusiasm for this intriguing and vitally important subject, and provide a reliable reference for experienced students and professionals alike.

"Ifyou wunt to atmin the possible, you must otrempt the impossible" (Rabindranath Tagore). Michael Schunke, Erik Schulte, Udo Schumacher, Martkus Voll, and Karl Wesker

Acknowledgments

First we wish tD thank our families. This atlas is dedicated tD them. We also thank Prof. Reinhard Gossrau, M.D., for his critical comments and suggestions. We are grateful to several colleagues who rendered valuable help In proofreading: Mrs. Gabriele Schunke, Jakob Fay, M.D., Ms. Claudia Ducker, Ms. Slmln R.assoull, Ms. Heinke Teichmann, and Ms. Sylvia Zllles. We are also grateful to Dr. julia )Orns-Kuhnke for helping with the figure labels. We extend special thanks tD Stephanie Gay and Bert Sender, who composed the layouts. Their ability tD arrange the text and Illustrations on facing pages for maximum clarity has contributed greatly to the quality of the Atlas. We particularly acknowledge the efforts of those who handled this project on the publishing side: Jurgen Luthje, M.D., Ph.D., executive editor at Thieme Medical Publishers, has "made the impossible possible." He not only reconciled the wishes of the authors and artists with the demands of reality but also managed to keep a team of five people working together for years on a project whose goal was known to us from the beginning but whose full dimensions we came to appreciate only over time. He is deserving of our most sincere and heartfelt thanks. Sabine Bartl, developmental editor, became a touchstone for the authors in the best sense of the word. She was able to determine whether a beginning student, and thus one who is not (yet) a professional, could clearly appreciate the logic of the presentation. The authors are indebted to her.

We are grateful tD Antje Buhl, who was therefrom the beginning as project assistant, working "behind the scenes• on numerous tasks such as repeated proofreading and helping tD arrange the figure labels. We owe a great dept of thanks to Martin Spencker, Managing Director of Educational Publications at Thieme, especially tD his ability to make quick and unconventional decisions when dealing with problems and uncertainties. His openness to all the concerns of the authors and artIsts established conditions for a cooperative partnership. Without exception, our collaboration with the entire staff at Thieme Medical Publishers was consistently pleasant and cordial. Unfortunately we do not have room to list everyone who helped In the publication of this atlas, and we must limit our acknowledgments to a few colleagues who made a particularly notable contribution: Rainer Zepf and Martin Waletzko for support in all technical matters; Susanne TochtermannWenzel and Manfred Lehnert, representing all those who were involved in the production of the book; Almut Leopold for the Index; Marie-Luise Kurschner and her team for creating the cover design; to Birgit Car1sen and Anne DObler, representing all those who handled marketing, sales, and promotion. The Authors

Table of Contents

Head

Cranial Bones

4

1.1

Skull, Lateral View ........•....•..........•.....•....• 2

4.1

Overview of the Cranial Nerves ........................ 66

1.2

Skull, Anterior View .......•....•..........•.....•....• 4

Cranial Nerves: Brain stem Nuclei and Peripheral Ganglia••• 68 Cranial Nerves: Olfactory (CN I) and Optic (CN II) .•....•.. 70 Cranial Nerves of the Extraocular Muscles:

1.3

Skull, Posterior View and Cranial Sutures •....••....•..... 6

4,2 4.3

1.4

Exterior and Interior of the Calvaria.....•....••....•....• 8

4.4

1.5

Base of the Skull, External View ..•.....•....••....•.... 10

1.6

Base of the Skull, Internal View ..•.....•....••....•.... 12

1.7

Orbit: Bones and Openings for Neurovascular Structures .. 14

Cranial Nerves

Oculomotor (CN Ill), Trochlear (CN IV), and Abducent (CN VI) ............................... 72 Cranial Nerves: Trigeminal (CN V), Nuclei and Distribution. 74

4.5

1.8

Orbit and Neighboring Strucb.Jres •.....•....••....•.... 16

4.6

Cranial Nerves: Trigeminal (CN V), Divisions ••••••••••••• 76

1.9

Nose: Nasal Skeleton ......•....•..........•.....•.... 18

4, 7

Cranial Nerves: Facial (CN VII), Nuclei and Distribution •••• 78

1.1 0 Nose: Para nasal Sinuses....•....•..........•.....•.... 20

4.8

Cranial Nerves: Facial (CN VII), Branches••••••••••••••••• 80

1.11 Temporal Bone •..........•....•..........•.....•.... 22

4.9

Cranial Nerves: Vestlbulocochlear (CN VIII) •••••••••••••• 82

1.12 Sphenoid Bone •..........•....•..........•.....•.... 24

4.1 Cranial Nerves: Glossopharyngeal (CN IX) .••.•.••.•.••.• 84 4,11 Cranial Nerves: Vagus (CN X) .......................... 86 4,1 2 Cranial Nerves: Accessory (CN XI) and

1.13 Occipital Bone and Ethmoid Bones .....•....••....•.... 26 1.14 Hard Palate ...•..........•....•....•.....•.....•.... 28

o

Hypoglossal (CN XIII) .. , , , .. , , , , .. , , , .... , .... , , .. , , 88

1.15 Mandible and Hyoid Bone ..•....•..........•.....•.... 30 1.16 Temporomandibular joint..•....•..........•.....•.... 32

4.1 3 Neurovascular Pathways through the Base of the Skull,

1.17 Temporomandibular joint, Biomechanics ....••....•.... 34

Synopsis .......................................... 90

1.18 TheTeethlnslb.J ..........•....•..........•.....•.... 36 1.19 Permanent Teeth and the Dental Panoramic Tomogram ... 38 1.20 Individual Teeth ..........•....•..........•.....•.... 40 1.21 Deciduous Teeth .........•....•..........•.....•.... 42

2

Muscles ofthe Head

2.1

Muscles of Facial Expression, Overview ..•....••....•.... 44

2.2

Muscles of Facial Expression, Actions • • • •• • • • • • • • • • •• • • • 46

2.3

Muscles of Mastication, Overview and Supertlcial Muscles • 48

2.4

Muscles of Mastication, Deep Muscles • • •• • • • •• • • • • • • • • • 50

2.5

Muscles of the Head, Origins and Insertions • • •• • • • • • • • • • 52

5

Topographical Anatomy

5.1

Face: Nerves and Vessels .............................. 92

5.2 5.3

Head, Lateral View: Superficial Layer. • •.•. •• .•.• • .•.• • .• 94 Head, Lateral VIew: Middle and Deep Layers •• • • • •• • • • •• • 96

5.4

Infratemporal Fossa . . . .. . . . .. . . . . .. . . . .... . .... . . .. . . 98

5.5

Pterygopalatine Fossa . .. . . . .. . . . . .. . . . .... . .... . . .. . 100

6

Oral Cavity

6.1

Oral Cavity, Overview . .. . . . .. . . . . .. . . . .... . .... . . .. . 102

6.2

Tongue: Muscles and Mucosa .. . . . . .. . . . ......... . . .. . 104

3

Blood Vessels of the Head and Neck

6.3

Tongue: Neurovascular Structures and Lymphatic

3.1

Arteries of the Head, Overview and

6.4

Oral Floor. .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .... . . .. . 108

External Carotid Artery . . .. . . . .. . . . . .. . . . .... . . .. . . . . 54 External Canotid Artery: Anterior,

6.5

Oral Cavity: Pharynx and Tonsils . . . . .. ... .. ... .. . . . .. . 110

3.2

6.6

Salivary Glands .. .. ... .. ... .. . . . . .. . . . ........... .. . 112

Drainage .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .... . . .. . 106

Medial, and Posterior Branches . .. . . . .. . . . .... . . . .. . . . 56 3.3

External Canotid Artery: Terminal Branches • . • • • • . • . •• . • . 58

3.4

Internal Carotid Artery:

7

Nose

Branches to Extracerebral Strucb.Jres . •• . • . •••• . • . •• . • . 60

7.1

Nose, Overview ...... .. .......... .. ........ .. ...... 114

3.5

Veins of the Head and Neck: Superficial Veins •••• . • . •• . • . 62

3.6

Veins of the Head and Neck: Deep Veins • . • . •••• . • . •• . • . 64

7.2 7.3

Nasal Cavity: Neurovascular Supply• . • •.•. •• .•. •• .•. •• . 116 Nose and Paranasal Sinuses, Histology and Clinical Anatomy .... .. ... .. . . . . .. . ............. .. . 118

IX

Table ofContents

8

Eye and Orbit

10

8.1

Eye and Orbital Region ...•....•...........•....•.... 120

1 0.1 Coronal Sections, Anterior Orbital Margin

8.2

Eye: Lacrimal Apparatus ..•....•...........•....•.... 122

and Retrobulbar Space ............................. 1 56

8.3

Eyeball •.....•..........•....•....•........... • .... 124

10.2 Coronal Sections, Orbital Apex and Pituitary.........•.. 158

8.4

Eye: Lens and Cornea .....•....•................•.... 126

1 0.3 Transverse Sections, Orbits and Optic Nerve ............ 160

8.5

Eye: Iris and Ocular Chambers ..•.....•.....•....•.... 128

1 0.4 Transverse Sections, Sphenoid Sinus and Middle Nasal

8.6

Eye: Retina ...•..........•....•................•.... 130

8.7

Eye: Blood Supply ........•....•................•.... 132

8.8

Orbit: Extraocular Muscles ••••••••••••••••••••••••••• 134

Atlantoaxial ]oint .................................. 164

8.9 Orbit: Subdivisions and Neurovascular Structures ••••••• 136 8.10 Orbit: Topographical Anatomy........................ 138

1 0.6 Midsagittal Section, Nasal Septum and Medial Orbital Wall ...................................... 166

Sedlonal Anatomy of the Head

Concha .......................................... 162 1 0.5 Transverse Sections, Nasopharynx and Median

10.7 Sagittal Sections, Inner Third and Center of the Orbit .•.. 168

9

Ear and Vestibular Apparatus

9.1

Ear, Overview ...................................... 140

9.2

External Ear: Auricle, Auditory Canal, and

9.3

Tympanic Membrane .............................. 142 Middle Ear: Tympanic Cavity and Pharyngotympanlc Tube 144

9.4

Middle Ear: Auditory Osslcles and Tympanic Cavity •••••• 146

9.5

Inner Ear, Overview ................................. 148

9.6

Ear: Auditory Apparatus ............................. 150

9.7

Inner Ear: Vestibular Apparatus ....................... 152

9.8

Ear: Blood Supply ................................... 154

X

Table of Contents

Neuroanatomy

lntroducUon to Neuroanatomy 1.1 1.2 1.3 1.4 1.5 1.6 1.7

Central Nervous System (CNS) ...•.....•....••....•... Neurons •.....•..........•....•....•.....•.....•... Neuroglia and Myelination .•....•..........••....•... Sensory Input, Perception and Qualities .•....••....•... Peripheral and Central Nervous Systems •....••....•... Nervous System, Development ..•.....•....••....•... Brain, Macroscopic Organization .•.....•....••....•...

172 174 176 178 180 182 184

2

Meninges of the Brain and Spinal Cord

2.1 2.2 2.3

Brain and Meninges in situ .•....•..........••....•... 186 Meninges and Dural Septa .•....•..........••....•... 188 Meninges of the Brain and Spinal Cord ..•....••....•... 190

3

Ventricular System and Cerebrospinal Fluid

3.1 3.2 3.3

Ventricular System, Overview ...•..........••....•... 192 Cerebrospinal Fluid, Circulation and Cisterns..••....•... 194 Circumventricular Organs and Tissue Barriers in the Brain 196

4

Telencephalon (Cerebrum)

4.1 4.2 4.3 4.4 4.5 4.6

Telencephalon, Development and External Structure •... 198 Cerebral Cortex, Histological Structure and Functional Organization •..........•....•..........•.....•... 200 Neocortex, Cortical Areas ..•....•..........•.....•... 202 Allocortex, Overview .•....•....•..........•.....•... 204 Allocortex: Hippocampus and Amygdala •....••....•... 206 Telencephalon: White Matter and Basal Ganglia •....•... 208

5

Diencephalon

5.1

Diencephalon, Overview and Development. . . . .. . . . .. . . 210

5.2 5.3 5.4 5.5 5.6 5. 7 5.8

Diencephalon, External Structure •• . • . • •. • . • • • • . • . •• . • 212 Diencephalon, Internal Structure . •• . • . • •. • . • • • • . • . •• . • 214 Thalamus: Thalamic Nuclei .. . . . .. . . . . .. . . . .. . . . . .. . . . 216 Thalamus: Projections of the Thalamic Nuclei • • • • . • . •• . • 218 Hypothalamus .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . 220 Pituitary Gland (Hypophysis) . . . .. . . . . .. . . . .... . . .. . . . 222 Epithalamus and Subthalamus . . . .. . . . .. . . . .... . . . .. . . 224

6

Bralnstem

6.1 6.2

Brainstem, Organization and External Structure •• . • . •• . • 226 Brainstem: Cranial Nerve Nuclei, Red Nuclei, and

6.3 6.4 6.5 6.6

Substantia nigra. . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . 228 Brainstem: Reticular Formation • . •• . • . •• . • . •••• . • . •• . • 230 Brainstem: Descending and Ascending Tracts •••• . • . •• . • 232 Mesencephalon and Pons, Transverse Section•••• . • . •• . • 234 Medulla oblongata, Transverse Section •• . • . •••• . • . •• . • 236

7

Cerebellum

7.1 7.2 7.3 7.4

Cerebellum, External Structure ....................... Cerebellum, Internal Structure•.....•....••....•....•. Cerebellar Peduncles and Tracts ...................... Cerebellum, Simplified Functional Anatomy and Lesions .

8

Blood Vessels of the Brain

8.1 8.2 8.3 8.4 8.5 8.6 8. 7 8.8 8.9 8.1 0

Arteries of the Brain: Blood Supply and the Circle of Willis Arteries of the Cerebrum ............................ Arteries of the Cerebrum, Distribution •...••....•....•. Arteries of the Brainstem and Cerebellum .••....•....•. Dural Sinuses, Overview ............................. Dural Sinuses: Tributaries and Accessory Draining Vessels Veins of the Brain: Superficial and Deep Veins ....•....•. Veins of the Brainstem and Cerebellum: Deep Veins ...•. Blood Vessels of the Brain: Intracranial Hemormage ...•. Blood Vessels of the Brain: Cerebrovascular Disease ....•.

238 240 242 244

246 248 250 252 254 256 258 260 262 264

9

Spinal Cord

9.1 9.2 9.3 9.4 9.5 9.6

Spinal Cord, Segmental Organization •....••....•....•. Spinal Cord, Organization of Spinal Cord Segments ....•. Spinal Cord: Internal DlvlslonsoftheGrayMatter........ Spinal Cord: Reflex Arcs and Intrinsic Orcults ........... Ascending Tracts of the Spinal Cord: Spinothalamic Tracts Ascending Tracts of the Spinal Cord: Fasciculus gracilis and Fasdculuscuneatus ............................

9. 7

Ascending Tracts of the Spinal Cord: Spinocerebellar Tracts............................................ 278 Descending Tracts of the Spinal Cord: Pryamldal (Corticospinal) Tracts .............................. 280

9.8

266 268 270 272 274 276

Descending Tracts of the Spinal Cord: Extrapyramidal and Autonomic Tracts.. . . . .. . . . . . .. . . . .. . . . .. . . . .. . 282

9.9

o Tracts of the Spinal Cord, Overview. . .. . . . .. . . . .. . . . .. . 284

9.1 9.11 9.12 9.13

Blood Vessels of the Spinal Cord: Arteries . • •. • . • •. • . • •. 286 Blood Vessels of the Spinal Cord: Veins .. . . .. . . . .. . . . .. . 288 Spinal Cord, Topography.. . . .. . . . . . .. . . . .. . . . .. . . . .. . 290

XI

Table ofContents

10

Sedlonal Anatomy of the Brain

12

FUndlonal Systems

10.1

Coronal Sections: I and II (Frontal) •.••.•.•.••.•.••.•. 292

12.1

Sensory System, Overview••.•.•.••.•.••.•.••.•.••.• 326

10.2

Coronal Sections: Ill and IV .•.••.•.••.•.•.••.•.••.•. 294

12.2

Sensory System: Stimulus Processing .•.••.•.••.•.••.• 328

10.3

Coronal Sections: V and VI. .•.••.•.••.•.•.••.•.••.•. 296

12.3

Sensory System: Lesions•.••.•.•.••.•.••.•.••.•.••.• 330

10.4

Coronal Sections: VII and VIII •.••.•.••.•.•.••.•.••.•. 298

12.4

Sensory System: Pain Conduction ••.•.••.•.••.•.••.• 332

10.5

Coronal Sections: IX and X •.•.••.•.••.•.•.••.•.••.•. 300

12.5

Sensory System: Pain Pathways In the Head and

10.6

Coronal Sections: XI and XII (Occipital) .•.•.••.•.••.•. 302

10.7

Transverse Sections: I and II (Cranial) ••••••••••••••••• 304

12.6

Motor System, Overview ........................... 336

10.8

Transverse Sections: Ill and IV ••••••••••••••••• • ••••• 306

12.7

Motor System: Pyramidal (Corticospinal) Tract •••••••• 338

10.9

Transverse Sections: V and VI (Caudal) ••••••••••••••• 308

12.8

Motor System: Motor Nuclei ........................ 340

10.10 Sagittal Sections: 1-111 (Lateral) ...................... 310

12.9

Motor System: Extrapyramidal Motor System and

Central Analgesic System •.•.•.••.•.••.•.••.•.••.• 334

10.11 Sagittal Sections: IV-VI ............................ 312

Lesions ......................................... 342

10.12 Sagittal Sections: VII and VIII (Medial) •.....•....•.... 314

12.1 0 Radicular Lesions: Sensory Deficits •....•..........•.. 344 12.11 Radicular Lesions: Motor Deficits •••••••••••••••••••• 346

11

Autonomic:: Nervous System

11.1

Sympathetic and Parasympathetic Nervous Systems, Organization .........•....•................•.... 316

11.2

Autonomic Nervous System, Actions and Regulation ••• 318

11.3

Parasympathetic Nervous System, Overview and

12.12 Lesions of the Brachial Plexus ....................... 348 12.13 Lesions of the Lumbrosacral Plexus ....•..........•.. 350 12.14 Lesions of the Spinal Cord and Peripheral Nerves: Sensory Deficits ..••....•.....•....•....•.....•.. 352 12.1 5 Lesions of the Spinal Cord and Peripheral Nerves: Motor Deficits •...••....•.....•....•....•.....•.. 354

Connections .........•....•................•.... 320

12.16 Lesions of the Spinal Cord, Assessment .•..........•.. 356

11 .4

Autonomic Nervous System: Pain Conduction ....•.... 322

12.17 Visual System, Overview and Geniculate Part .......•.. 358

11 .5

Enteric Nervous System .•....•...........•....•.... 324

12.18 Visual System, Lesions and Nongeniculate Part •....•.. 360 12.19 Visual System: Reflexes....•.....•....•....•.....•.. 362 12.20 Visual System: Coordination of Eye Movement.•....•.. 364 12.21 Auditory System ...••....•.....•....•....•.....•.. 366 12.22 Vestibular System ..••....•.....•....•....•.....•.. 368 12.23 Gustatory System (Taste) ............ .. ............. 370 12.24 Olfactory System (Smell) ..• . .... • . . .. • . . .. • . . .. . • . . 372 12.2 5 Umble System • • . .. • • . ...• . .... • . . .. • . . .. • . . .. . • . . 374 12.26 Brain: Fiber Tracts .. • • . ...• . . . .. • . . .. • . . .. • . . .. . • . . 376 12.27 Brain: Functional Organization . .. • . . .. • . . .. . . . .. . • . . 378 12.28 Brain: Hemispheric Dominance . .. • . . .. • . . .. . . . .. . • . . 380 12.29 Brain: Clinical Findings . .. . • . . . .. • . . .. • . . .. • . . .. . • . . 382

XII

Table of Contents

Appendix

List of References Subject Index .................................... 387 .•.• • ••.•.••.• • ••.•.••.• • ••.•.•••• • •.••.• 389

XIII

Head Cranial Bones • ••••........•••• ••.....•• •••• ••.... 2 2

Muscles of the Head ........... ........ ..... .... 44

3

Blood Vessels of the Head and Neck . ••••••••••... 54

4

Cranial Nerves •••••••....•••• ....... •••••••••.. 66

5

Topographical Anatomy ...•••• ••..... • • •••••• ... 92

6

Oral Cavity .. .. ... .... .. ... ............ .... ... 102

7

Nose ......... ........ .. ... .............. ... .. 114

8

Eye and Orbit . . . ........... ........... . ....... 120

9

Ear and Vestibular Apparatus ..... .... ... ........ 140

10

Sectional Anatomy ofthe Head ...... ........... 156

Head - - 1. CmtifJI Bones

1.1

Skull, Lateral View

SqU~~T~CUS suture

Nubone

lnfrliGrllltll - -'?!.----'"\ foramen

A latil!ral'llfewoftflukull(cnnlum} Left later.al view. This view was seledl!d as an introducti~:~n to the skull because It displays tfle gre
2

follow. This unit rellfews the prfndp.al rtructures of the lateral aspect of the skull. The chapter as a whole is intended tD familiarizl! the reader wlth the names fAtheaanlal bones before proceeding to finer ~Ntomi­ cal detills and the relationships of the bones to one another. The teeth .ilre descrfbed In .il Sl!parm unit (see p.l6fl).

Head - - I. OVnJGI Bones

Tempor.ll bene, squamous part

P;u!etll bene

Mlndble

I l.atief.JIIIfewof the cr.Dill bones Left lateral VIew. The bones are shown In different colors to demonstrate more de.-.rly theirextef'lts and boundaries.

C Bona of the neurocnnlum (lri!Y) and vlsa!rocr.lnlum (or.mge) Left I.Jte!'al VIew. The skull form sa bony capsuleUlat encloses the brain, sensory organs, and viscera of the head. The greab!r size of the neu~ cr.ilnlum (cr.ilnlal \'iult) relillive to tfle Vlsarocranlum (fadal skeleton) Is a typiC.ill pdmate fu.rture directly correlated 'With the larger pr1mare brain. E Bones of the neurocnntum ;md llfscerocr;~ntum Newac111nlum (gray)

Vlsceroa-anlum (or•ge)

• Flontal bone • Sphenoid bone (excluding the

• Nasal bone • l.aalmalbane • Ethmoid bone (excluding the alblfronn plate) • Sphenoid bone (pterygoid process) • Milllllla • Zygomatlc bone • Temporal bone (tympanic part, styloid proceM) • M~ndlble • Vomer • Inferior n.asal turbil\lte • P<~lallne bone • ~ld bone(seep.31)

pt«ygold proeMS)

•

Tempor~lbone

(squ..mous part. petrouspart) • Parld31 bone • Ocdpltal bone • Ethmoid bone (albrtronn plm)

D Os:sffk:iltlan of thecr;~nt;~t bones Left tater.ill VIew. The bones of the sla.ill either dewlop directly from mesenchymal ronnective tissue QntramembraAOUS assification, gr.ty} or form Indirectly by the osslflC
F Bones of the desmiKT.Inlum .1nd chondrocr.mlum Chonllhcl'llnlum (blue)

• • • • •

• • • • •

Nasal bone Laaimalbane Maxilla Mandible Zygomatic bone Frontal bone Parietal bone Ocdpltal bone (upper ~rt ol the squama) Tempor~l bone (squ..mous part, tym~nlc part) P;~laane bone

• Ethmoid bone • Sphenoid bone (-luding the medial plm ofthe plli!\'Wald proeMS) • Temporal bone (petrous and mastoid parts, styloid process)

• Ocdpltal bone (excluding the upper part of the squama) • Inferior nas.1l turblnite • Hyoid bane(seep.31)

• Vomer

3

Head-- 1. CmtifJIBones

1.2

Skull, Anterior View

FIOOt
P
S~,J~n~orllltal

foramen

m~rgln

NIL'wllbone

Sphl!flOidbone. greab!rwng

Sphenald bone, lesser wing

Temporal bene

Orfllt

Eitlmaldbone, pe~pendlcular

plm

Sphl!flOidbone. greab!rwng

lnfraorbltll

Zygomatic: bone

""'111'"

Plrffonn (anterfar

t.'lckleoi5011 llCH'ICha

1'111111) lperWn!

Max! I~

Vomer

A At*rforvJewoftheskull The boundaries of ttle facial skeleton (vlsc:erocr;mlum) can be dearly appr«lilted In ttllslllew (the lndMdual bones are shown In B). Tbe bony margins of ttle ant:erior nas.1l aperrure mark the start of the respiratory

tractlnttleskull. The nasal cavlty,llkettleorblts,cont
4

(the olfactory mucosa). The poru,_l slnllm a~ shown schematically In c. The anterior view of ttle skull also displays the lhree clinically Important openings through which sensory nerves pass to supply the face:

the supraorbital foramen, infraorbital foramen, and mental fDramen

(see pp. nand 93).

Head - - J. CranlaiBones

c===

~FIVnbllslnu•

- Ibon.• P:lrlotll bon~ sphe.n old...__ .~\ling

Notal bon~

Temporal bane

Mlddu...t condlll

Sphenoid bone.

lnfe1ornallf

l)gomrdc bon~

g~Yoing

sphenoid nua

~ MDIIlaryslnus


i'Msal~

MDIIla

~I

pllor ~--

Yertlaol --~~'I

:..::::;;;

Ethmoldool.ls

c ...r.naulslnuses: pneurnMizniOn nghtretts the bone AntErior view. Some of the bones of the fadal skeleton are pneumatized, I.e., they contain al~lled cavities that reduce the tntal weight of the bone. These cavlttes, c.alled the p;tr.masal sinuses, commu nlcate with the niiSoill cavity and, like It, ire llned by Clllltll!d respiratory epithelium. lnflamrNtions of the pal"iinia.il sinuses (sinusitis) and assodmd complaints are very common. Because some of the pain of Jlnusltls Is projected to the skin overlying the sinuses, It Is helpful to know the proJections of the slnu:ses onto the surface ofthe skull.

Horllantll >ygornotlc pilar

~millie

pillar

•

II

Horimntol ZV!!Omlllc pillar

D Prbdptllnes of fora (blue) In the flclilllbleton Anterior view, b ~ten! view. The pneumatized paraNsal sinuses (C) have a mechanical counterp;art in the thickened bony "pollars• ofthe facl
11

E LeFort dilalfleiltlon Ill mldf.S.I hdUI't$ The frame-llke construction of the fadal skeleton leads tD characteristic p;~ttems of fracture lines In the mldfaclal region (LeFort 1,11, and Ill). LeFort I: This fracture line runs icrvss the maxilla and ab~M: the hard p;tlate. The maxllli Is 5eparited from the upper ficlal skeleton, disrupting the integrity ofthe maxillary sinus (low 111mswrse(rudure). LeFort II: The fricture line passes across the niiSoill root. ethmoid bone, maxilla, and Z)'!IOrllitlc bone, creating a pyramid frudu~ that disrupts the in~grity of the orbit. LeFart Ill: Thefidal skeleton Is sep;t rmd frvm the base of the skulL The main fricture line p;~sses through the omits, and the fricture rNY addltloNIIy Involve the ethmoid bones, fronul sinuses, sphenoid slnu:ses, and zygomatic bones.

5

Head-- 1. CmtifJIBones

1.3

Skull, Posterior View and Cranial Sutures

5~1------~-----------------sutin

umb6cld

subJre Oaipltil piiM

Temporal bone. 5qUIMOUS p;ut

Supreme

nuchal~~

Superior nuchal~e

lnfenct nuchalllne Vomer

Ot'Cipltil

Temporal bone, pdi'Ousp;ut £mm.1l ocdp'it;ll prot11beranae

Mast!illd fa ram~

Temporal bone, mastoid proatiS

~

A Posterfonfew of U!e skull Tbe ocdplt.ill bone, which Is dominant In this view, articulates With the p.arietal bones, to which it is mnnected by the lambdoid subJre. The mnlal suwres are a special type ofsyndnmoJis (•llgammtouJ att.ilch·

6

ments that ossify with age, see F). The ower surface of the ocdplt.ill bone Is contoured by musaJiar origins and Insertions: the lnfertor, superior, arld supreme nuchalline.s.

Head - - I. OVnJGI Bones

Temporal bent. squamous p;rt Tempon~l bent.

petrQwp;rt

D C'nlnllll deformltfts due to the prerNQI~ dosu~ of cranllll sutures The premature dosure of a aanlal suture (craniosynostosis) may lead to characteristic cranial deformities. The foii0Wif19 sutures may close prematurely, resulting in various cranial shapes:

8 Postelionfew oftfle cnnlill bonts Notr: Tbe temporal bone consists oftwo ma1r1 parts based on Its embry· 011ic development: a squamous part arid a peb'Dus part(see p. 22).

a S.agitbl suture: scaphocephaly (long, narrow slwll) b Co~l suture: oxycephaly (pointed skuiO c Frontlll suture: trigonocephaly (triangular skull) d Asymmetrlcill suture closure, usually ln~ng the coronal suture: plagiocephaly (asymmetrical skuiO

Ant.!r!or -----,-...:~

fontlnele

-

PosWior

fon!anelle Llmbclold

suture

•

• E HydroGI!flhillus ;mel mlcnocepflaly suture Coronal suture

- "'""'=- ---1

b

C 111e nll!llniltiillslalll • 1St later~! view, II supenor lllew. Tbe flat cranial bones mlllt grow as the brain expi!nds, and so the su· t:ures betwemthem mustremalr1open forsometime(see F). In the neo· nate. there are areas betweer1 the stlll-growlr~g cranial bones that are notoccupledbybone:tbefonunelles. Theycloseatdlfferenttimts(the sphenoid fontllnelle in about the 6th month of lif\!, the mastoid fonta· nellelnthe 18th month, theantalorfor~tanellelnthe 36th month). The postvtor{ont!IMI/e provides a refa'ence point for describing the position of the fetal head during childbirth, <md the antl!tlor{flntx:mel~ provides a possible access sitJ! fDt drawing a cerebrDSpinal fluid sample in infants (e.g .• In suspected meningitis).

• Characterfstfc cranlalmolllhology In hydroCfll/Hllus. When the brain becomes dilated due to cerebrDSpinal fluid accumulation M{rw the cranial sutures O$Sify (hydrocephalus. "water on the brain"), the neunoaanlum wlll expand while the facial skeletor1 remains unchar~ged. b Mlcroa!phalyresults from premature closure of the cr<mlal sutures.lt is characterized by a small neuroaanium with relatively large orbits.

F AIJut which tfle prfrtdpal sutures ossify Suture

••-lftatlon

frantill suture

Childhood

Saglttll suture

20-JOyears of age 30-40ye.arsohge 40-SOyears of .age

Con10al suture

umbdold suture

7

Head -

1.4

T. CrtlniGI Iones

Exterior and Interior of the Calvaria

Fruntll bane

Fruntll sl.....

O.:dpltll bGne

A !Extl=rfllf (•) •ncllnterfDr (b) Gfthe u1Rrf1 The extemil surface of the alvarla (•) Is relaUvely smoodl, unlike Its lntamal surfiCI!! (b). It Is defined by the fronbl, JHrletal, ind ocdpltal bones. whic:h are intercon~ by the CD~Uni!l, Jll!littill, and lambdoid sutures. The Jmooth external surface Is Interrupted by the ~rietal foramen, whlc:h giYeS JHSSage to the JNrfetal emls.sary win (see F). The lntemi IsurfaCI! Df the Ciilvarla also bean a number Df plts and gro~MeS: • The granui.Jr foveolae (smill pits In the Inner surface Df the skull caused by sacrular protrusions Dfthe arachnold membrane ~ng

the brain) • The groove for the superior sagittal sinus (a dural voenous sinus Dfthe

brain, see Fand p. 65)

G........ rw s._tor ygttol sha

PllrleUI fwamen

• The arter1al groavu (which mark the positions Df th.e arter1al wssels af the dura mat«, such as the middle meningeal artery which supplies most of the dura miter and tMriylng b11ne) • The frontal aest (which gives Olttachmentto the fabtCI!Rbrl,a sickleshaped fold Df du ri miter between the cerebral hemispheres, see p. 188).

The frontal sinus In the frontal bone Is also visible In the Interior YII!!W.

8

Head - - J. CranlaiBones

FrollUI -~---:­ bone

P..-1 bone

r: lh! salp and miVIIrtll Note the three-l;oyered strurnl'l! of the calvaria, consisting of the outer table, the dlploi!, and the Inner table.

B Extertor ol the miVIIrtll viewed trom llbGft

The dlploi! hu a spongy struct\lre and conulns red (blood-forming) bone man-. With a phasmacytorn;~ (malignant transformation of t8'taln white blood cells), nna ny srn;~ll nests of rumor cells may destroy the suft'Dunding bony trabeculae, and radiographs will demonstr.rte multiple lucent areas ("pcmched~ lesiO!U") In the skull. Vessels called m~­ lssrlry wins may pass through the calvaria to connect the w.nous sinuses of the bl"iiin with the wins of the scalp (see panels E
D Se111111¥1tyvfthe lnner&lble tD tnum1

SUperfor

The Inner uble of the c.Jtvarlals wry sensitive to extm!al tnuma ;md may fracture - n wh~ the outer table teT~ains intact (look for correspcmdlng e¥1dence on CT Images).

HlltQIStllll

I

r ~1=____---r ==of

n-........... --::-~____: "r.:f-.:.0.,:::-+- -rkr

sinus

- k=-"'-"'-"---'-=-.,---- Ocdp~l

temporal

emlssllyvdn ~Po"+- Mos!Did

dlplolcwln

emllsorywln

Oa:~l

L.,.l~~---

dlplalcwln

a.nd)iar emllsorywln

External -~~+---'11~~

wrtS>ral wnaus plaus E Dlplok wlnsln the alvlrtl

F Emissary w1111 af the ocCiput

The diploic wins are loc.Jted In the cancellous or spongy tissue of the cranial bones (the dlplol) and are visible when the outer table Is remowd. The diploic winJ communicab! with the dur~l-us .sinuses and seal p wJns by w-.y of the emissary w:lns, whim autr a potential route for the spread of Infection.

Emissary w:lns establish 1 direct con nectlon between the dul"iil venous sinuses and the extruril nl;ll wins. They p.liSS through pn!formed CTillnlill openings such 01$ the parietal foramen and mastoid foramen, The enliss;ny veins are of cllnlc.JIInterest because IIIey may allow b.ictrrli from the scalp to enter the skull along these w.lni and Infect the dUl'il mmr, causln51 menlnStltis.

9

Hftld -

1.5

'· Cranlol Bones

Base of the Skull, External View

~·bone

~""nebont

fronalbone

lnfsiornaAI mnch•

.51Wnold bone

vomer

Tl!fT'4XIralbone, zygomallc pro«$$ T'tfl'9aral bone, fqUIITIOUJ part Tl!fT'4XItilbone, tyn'4)1nlc part fl!fT'4XI18Ibone, petrcus Pll't. mastDidp.1rt

Foramen INgl&m

Oo:lpllal bone

A Iones of tfle bae ofIitie llkvl lnfelforvtew. The bue oft11e 51rullls composed of a mosak-llk.e assembly of v~rious bones. It is helpful tD review the shape and location of

these bona before studying further details.

tolldele cranlolr-.

:;.:...._ _ _ _ _ CMalld

canal

B lb!laUonshlp of the fvnm~~~lamrum ta tfle Arotld C3Nil and lnternlll carotid •rtery Left lateral view. The for1men lacerum is not a true apature, being occluded In life by a 1aytr of fibrocartilage; 1t appears illS an opening only in the dried slwll. The foramen l~cen.m is dosely related tD the carotid c;mal and tD the Internal carotid artery tiNt travenes the canal. The gIHII!r petrosal nerve and deep petrosill nerve ~s 111 rough the foramen laten~m (see pp, 81, 85, and 90).

10

foraonen

locerum

Head - - I. OVnJGI Bones

lnd'sllle

fa ramen

Maxilla, pala1!ne prcu:ess

Gremrpalatlr~e

foramen

Vomer

~~0~~.---~~--------~~ medial platJe Ptl!rygokl proc:ess, - - - - ';,-- - - ' - - - ----.11 lilti!I'
Forame>owle Foramensplnowm

= -------...i._.. .,., ----:------L.-:

l'oramenlaal'um _ __;,:....__ _ ___,.....l!J~~~.,....--§ ~d~l--~-~----,~~~. .

Jugulufar<~men -----d,::::;i;i~~~·_.-;

..l:=o"ii!.,J-----l· - -1-- - Ocdp'lt.llcon~¥e

.......:~

T--=r- -

Sl)1oiTIII!Jiold fa ramen

Masto~ ()n)Ct$S

ttypogmsal

canal Foramen magnum --~r-- Masto~

foramen

r~or--~~~---­

nuchalltle

~~r------~~--­

nuchallne

-----::::::-<-'-="--==:r------ Exb!mllocdplal pn~lllberant1!

C The~lllhapectoftheskul lnfertorvlew. The principal extemal features of the biseofthe skull are labeled. Notl! particularly the openings that transmit ne!'VI!S and Ye$· sels. With abnormalities of bone growth, these Ol)enings may remain too small or may become nal'!'lliWed, compressing the neui'O'r.lsaJiar

structures that pass through than. Ifthe optic canal falls to grow normally, It may compress and damage the optic nerve, re.51JII1ng In visual fleld defeds. The symptoms associated With these lesions depend on the affected opening. All d the sll'uctlJres dl!pidl!d here will be mnsi~ ered In more det
11

Head-- 1. CmtifJIBones

Base of the Skull, Internal View

1.6

Jugum

---'~-----...

sphenolclale ·IO"!~:IfP'-._..

- - - Temporal bone, squamous part

.aiiiiiio....-'- - LHser...tngof

~naldbone

' Foramen

---Middle

cranial~

____:~~~

~..,

~tlor ---"::+-......:.,~-

CI\lnlalf(ISgo

• A BoM!iofthe baseoftheslaJII,IrrtHnalvTew Diffi!tef'lt colon are used here to highlight the arrangement of bones in

Middle cn~nlalfll556

the biiSe of the skull as seen from within the cranium.

F~~n~ --~~~~~~~~ pillar

"pillar

tr.II\SWI'Se --~~-

l'tBygald - --.l,__.l.L.....,.¥.'1 plllr

Vl!l'tlal zygcm.Jtlc pillar

Posb!r!or mnlalfossa

l'cnlmen

b

. ..-r;~r-~mn~

m1!J1Lm

zygomatic:

pillar

B

TMcnnlllfosne

a lntl!rlorlllew, b mldsaglttal section. The l'ntei'Jorofthe 5kull base~ not ~~+-~ot tr.III$\OeiSe

pillar

fl~t but is ~ w form three sua:essille fossae: the anterior, m~ die, and posterior a.-anlal fossae. Thesedeprenlons become progruslvely deeper In the frontill·tx>occlpttal direction, forming a terraced arranger menttllat ~displayed most dealiy In b. Thecranial f\ns~ are bounded bythefoi!Qwing structure$:

• Anterior to middle: the le$Ser wing5 of the sphenoid bone and the jugum sphenoldale. • Middle to posterior. !he superior border(rfdge) oftile petrous part of the temporal bone and the donum sellae.

c Bale ofdie skull: prf!Mfpalllnes of~ and _.,..mDII fl'ldllre lines a

Prlnclp;~lllnes of force, b common fr.-acture lines (Interior views). In response to masticatory pressures <md oCher mechanical stresses, the bones of the skull base are thicla!ned to fonn "pillars• along the prin·

clp;alllnes of force (comp;1re with the force d!str1but!or1in the anterior view or1 p. 5). The Intervening areas that are not thickened are sites of predl!ectlor1 for bone fradllres, resullfng In the typical pilttems of basal skull fracture lines shown hen!. An analogous phenomenar1 af typic.al fracture lines I~ found In the mldfadal reglor1 (see the anterior views of Lefort fractures or1 p. 5).

12

Head - - I. OVnJGI Bones

Eltlmoldbcn~.

cl'ktagalll

F-lbone

Sphenoid baM.

l"oolll\8l

sp!nosum Altl!!lal

grocwe

lesse'v.lng Sphenoid bone. ptl!riMng Sphelold bon~. hypo~lfoua

F«llm81 IICI!I'Um

Clllllls

Hypoglas:~~l

anal jugulu lor<1l11el

c-for $1grnold

FOI'Mnen ""SJMUm

linus

Cmbellar fosl:a

G!'OO'tefor lr.~svene

slnU'J

UMralf05.\i

D lrrtmarof the baR ofthulcull It is interl!sting tD ccmp;~l'l! the openings ill the interiar of the base of the skull with the openings visible In the external vlew(see p.11 ). These openings do not alwiys colndde bec:.1use some neurova1cular struc· tures change direction when passing throcJgh the bor~e or pursue a rela· tively long intr.lo$Seous course. An example of this is the inb!rn~l acous· tic meatus. through which the facial ne~W.. aiTIOilg other structures. p;~sses from the Interior of the skull Into the petroU5 part of the tenn· por.al bone. Most of Its ftbers then leave the petrous bone through the stylom;moid for~men, which is visible from the external ~pect (see pp. 80, 91. and 149 for further details). In learning the sites 'Where neurovascular structures pass through the base of the skull, It Is helpfullnltlally tD nat2 whether these sltl!l are

located In the anterior, middle. or postenor cranial fossa. The .mangement of the crallial fossae is .shown ill B. The cribriform plate of the ethmoid bone connects the nasal cavity with the anterior cranial fossa and Is pertor.~ted by numerous forimlni for the p;~ssage of the olf.lctoryfl. bers(seep.116). No«!: Bec:.1use the bone is so thin in this~~.~ frontal head injury may easllyfracturetheafbr1form plateandlacer.~tetheduri mater. allowing cerebrosplnil fluid to enter the nose. This poses a risk of meningitis, as bactena from the nanstenle n.u.al CON!ty may enter the sterile cerebrospinal fluid.

13

Head-- 1. CmtifJIBones

1.7

Orbit: Bones and Openings for Neurovascular Structures

8 OpenlnSJI In the ortlltfor neui'VIIiii5Cular structures Nfl~: The supraorbital foramen is an important

site In rvutfne clinical examinations because the examiner presses on the supraorbltll rfm wtth the thumb to te.st the sensory function of the supraorbital nerve. The supraomitll nerve Is a terminal branch of the fll'lt dlvlslon of the trfgemlnal nerve (CN V1• seep. 76). When paln Is present In the dlstrlbutron of the trtgemlnal nei'Vt', tCS'Idemm to pre$SUre may be n~ted ;at the supr.1orbltill site. Open... or

....... Optic: canal

• Optic nel'lllt (CN II) • Ophthalmic arterr

Superfor orbltill

• Oculomotor nerve (CN Ill) • ~chlear neM (CN IV) • Ophthalmic neM (CN V1)

f.ssure

-Laalmaii'M!I"'Ie - Frontal nerw - Nasoclllary nel'lllt • Abducent nel'lllt (CN VI) • Superlorophthalmlcwln

Inferior orbital

fissure

• Zygomatic neM (CN V;!} • lnfl!rlor ophthalmic vetn • lnfr.10rbltal artery, weln, and nel'll'l' (CN V'J}

• Nasolaalmal duct

lnfraorbltill Zygomatic:---+bone

MaJillla

--~r-----5~~~

-7~~-~

greale-wlng

wln,andnem

anal Supra· orbital

foramen Front.'!I

c

• Infraorbital arwy,

• Supraorbital artery • Supraorbital neM (latefal branch)

InCisUre

• Supratrod11ear artery • Supraorbtt
Anterior ectlmoldal

• Antll!l1or ethmoidal artefy, win, and nerve

foramen A Bones of the rtght orbit Anterior vlew (•). later.~l view (b), and medial view (c). The lilta"al orbltill w.~ll has be\!!\ 1'1!1Yloved In b, and the medial orbital wall has

beftl1'1!1Yllllll!!din.:. The orblt Is formed by seven different bones (tndic.rt:ed here by color shading): the frontill boDe,. zygomatic bone. maxilla, ethmoid bone,

14

sphenoid b~ne (see a and c}. and als~the lacrimal bone and palatine bone, wfllc:h are visible only In the medial view (see b). The present unit deak with the bony anatomy of the orbits themselve$. The relationships of lfle orbits t» each 01fler are described In the next unit.

Posterior ectlmald~l

foramen

• Pom!rlorethmold;al artery, weln, and nerve

Head - - I. OVnJGI Bones

FnxrtllllndS\U't' S~.pr.~arflltll-

ilr.amen

Postufar et!lmoklal fcr.amen

Frant.11bone. cdlltllpart

Antl!rfar el!lmoklal fcr.amen

2MiamllkD-

Optic anal

orblbllfar.~men

1\lmlbone

Supe!or cdlltll l'lsiure

MildIIa. fro lUI p!'OO!S $

Z)'gOmatlc

bone lnfl!rfor cdlltll fissure

lolafmal bon~ Ethmoid bone. adlltll plate

lnfraarflltll

9'0Madia, Clbltll surfaa!

lnfraorbltll foramen

Antl!flor lia!m11 am(lllilldl•l

ahmoklbone Optic c;anal

~qf llcrl~lsac

(I'Alttopenlng forl\iiiOiia!~l

Glct)

._.,

.#t

Frantol bone. arfllt.ol suoiact'

b

c

lnfetfar adlltll ftssu re

Openl'nglln the right orfllt for nl!llrovruaJiarstructiJres

Anterior view (a), lateral view (b), and medial view (c). The lateral orblt.ll w.~ll has been remcwed In b, the medial orbital w.rll In c. The followIng opa1lngs for the pass.1ge of neuF'O'r.l1aJiar structures (see listing In B) can be ldernlfted: the supenor and lnfl!dor ortllt.ll flssures (a-c), the optic canal (a, b), the anterior and posterior ethmoidal foramina (b, c), the Jllf'raorbttal g~WVe (<~),the lnfraortllt.ll canal (b, c;), and the lnfr.rorblt.ll foramen (011, b). Dlillgram b shows the or!flce of the nasolacrimal duct. by which lacrfmal fluid is conveyed to the inh!rior muW$ of the noM!. The lateral view (b) demonstrates the funnel·llke structure of the orbit. which funcUons like a socketm cont.lln the eyeball and constrain Its mOIII!rnents. The lnh!rtor ortlltal flssure operu Into the ptzrygopalaUne fossa, which bonders on the pDS!J!riarwall of lfle maxillary sinus. It contorIns the pmygopalatine ganglion. an lmpoltlnt component of the parasympathetic nervo~~S system (see pp.81, 101). The upper part of the exposed maxJIJary sinus bears the o.suum (In the milldllary hiatus) by which the sinus opens into lfle nas.al cavity superior to lfle inh!ri~:~r concha (see pp. 2o-21 ).

15

Hftld- '· Cnmlollones

1.8 Orbit and Neighboring Structures

1 Olnlcally lmpclfUllt relltlonlhi.Hc..n the orllltland sumaundlng

.......,.,................... ....... ICnldllres

lmr'ior

Wlmoldalls

Supelfor

• Maillary liinus • 11-onbl Sinus

•

Suporior orb~l

Anmrlorc:r~nlll fosSil

(contJins dwfronuol

ft..ureOad5 to middle

lobuofthe br•ln)

cr.onlolfauo)

Mallbwy sinus

Mldial

• Ethmoid cells

Dtep« stNctum that haw 1 dinically lmparant r8iltlonshlp totha orbit • Sphenoid slnU&

A BaMs crf thnrttltnnd ed)lftllt cavtt1111 The color-coding here b the ~me liS for the bones of the orbit on pp.14-1 5. 'These bones also fonn portions of the Willis of neighborin11 ciiVIUes. The following ldjicent structures are visible In the diagram:

• Antaiorcranial ross.. • Frontill sinus • Middle cr~nlal foSA

• Ethmoid cells' • Maldllary sinus

• Mlddlecr11nl'l foss1

• Optic c:hl&sm

Disease processes may originate In the orbit ~ nd spread to these cavities, or orlg lnm In these C
• Pltulblry

• c-mousslnus • l'tt"''!!opliltlne fossa

• The Rrminologio AnolomiaJ NS drapped

the term 'ethmoid sinus' In filvor of 'eth· mold cells..'

otsto

Flollbl bGne. ertobl surfm!

golll

Spllenald bc!N., '-'twlllg Elhmold bone.

OpllcCIJiill

pe~p~ndlallor

plllle El!lmolclbon~

ort.IUI ...

s~

arbltMftmn

(lornln• PiP\'riiCN)

Sl4)011or ,_la>ntm

Orblbolsurlloz. gutrwtlg

Zygomotlc: bone. ariolt:.I!Oirliu:e

lnflftar orblt.l ftssure

lnlriortitil

OrtiiQift-

aMI

Middle naiGDn!N

Mildlory

sinus Polatlne

pnxmofthe I!Midli

C Ortolb ilnd1Wighboftn1 ltnldllnll

Coronal sect1on through both orbits, * - d from the front. The walls sepuatlng the orbit from the ethmoid c:ells (o.3 mm.lamlna papyr.~ceii) .-.nd from the mMIIII ry sinus (0.5 mm, orbital floor) are very thin. Thus. both of these walls are susapbble to li'actunl!s and providll! routes for

16

the spsnd of tumors .-.nd Inflam mltory processes Into or out of the orbit. 'The superior orbital fissure communlutll!s with the middle aanlal fossa. and so sevm~l stnlttures that are not pictured he~the sph~ nold sinus, pltulury g.land, and optic: c:hlas~re .-.lso c:JOM!y related tD theorbil

HeGtl - - I. OVnJGI Bones

l'fantalbane. zygomatic: procHS

Ethmoid

(i->Oing. tl!nlporalsurface

~

I

bane

Ternporal bane. squama ~a part

I

lnfu'lor Spheno-

SphtMpallnle

5quamau5 5ublre

~ma'l

~ p;~lltlne

foss;~

Maodlary

Seedet.111

tu!Mroslty

lnF

orfllt.1l

IIWJre Cho;na

Temporal surfaae

hlltfnebane. ~nmldal p!'OCHS

lnfratl!m· poralcn!rt

~d

Pl:efygold

proc:HS,

~

mecfal plate

lmral plate

Fanunen '!llnasum

l'terygald

hamulus

D CIOSHJp111tw oftfle left ptll!f)'gopalltlne llilsM Lareral view. The ptl!rygopalatlne fona Is a crossro;rds between the middle cranial fo~a. orbit. and nose, being travened by many nerves and vessels !flat SIJpply lhe.se s!JIIctures. The ptl!rygopalatlne fossa Is mntinuous later~lly with !he infratemporal fossa. This diagr~m shows the lareral appro;rch w the ptl!rygopalatlnemsa through the lnfr.ltem· poral fossa. wfllch Is utllrzed In surgkal operations on tumors In this re· glon (e.g., nasopharyngeal tlbroma).

l'llCIJndum

bone.

Fe ramen

~d

Grt>a12r - ----l palatl'lecanal

l'rom:

Middle cran~l fossa

•

Pteryogoid anal (Vldlan canal)

Skull base (Inferior surface)

• GreiltJer petn»al nerve (p;~rasymp;lthetic branch ofhcfal nerve) • Deep petno5lll nerve (sym()ilthetlc llben from carotid plexus) • Artleryofpteryogoidanal with accomp;~nylngvelns • NeNe of pterygoid anal

Greater p;~latlne

Palate

• Cre.rterpalatlnenerve • Desoendrng paliltlne artery

rotundum anal

~litlne

fossa

F ConnectSons of the left pWftllpalltlne llilsM wttfl1djacent ~

Detail from D. The content3 of the ptefygop;rlatlne fossa Include the pterygop;rliltlne ganglion (see pp. 81, 101), 'Which Is .m lmpoi'Unt

G'Jille

E Structures adj1u:enttD tfle l'l!llt ptl!ryg~~p~llltTne Inferior view. The arrvw lrldlcates the approach to the pterygopalittlne ~sa from the skull base. The fossa Itself (not visible In thlsvlew) Is lateral to !he lateral plate of !he ptefygold process of the sphenoid

........,. FG1men

Fcnmen

anal (foramen)

ganglion in !he parasympathl!l:ic nervous system.

~ll~rynerve(CNVz)

• GIUtJerpalatiMartery

Laser palalfne canals

P~late

• I.J!:aer p;~latlne nerves • Lesser p;~latlne arteries (tennrnal branches of

SphenopalatiM

Nasalavity

• Sphei'Aipalatinurtery (pluuc:mmpanyrng lll!fns)

descending palllt1ne artery) loNier1llg llniCIUN

Anterior

hlramen

• lateral and medial supel'lor

Malllarytuberollty

J)OSWrlor nasal brancl1e$ oflhenasopalaane ner\11!! (CNV.z)

l'tlell!loldpi'Oa$$ filelllendlcular plate of llle palatine bone lnfmemporal fossa {via the ptiefygomaldllaryfl.ssure) Ciremer >Oing of the sphenoid bone, junction

w11h the lnftrlarorbltal fissure

Inferior

RA!InJpharyngeal space

lnf!rfor orbital fl.sure

Orbit

• Infraorbital nerve • Zygomatic nerYI!!

• Orbltllbrancl1es(ofCNV.z) • lnfraorbltllartery(plus accompanying verns) • lnferiorophlllillmicvein

17

Head-- 1. CmtifJIBones

1.9

Nose: Nasal Skeleton

l.olt2fal--....,.:nasal artbge

Naris

i

Septlll CJrtiLllg~

Major alar

,___ _ Anll!r'lor

arttage

nasal spine Minor c.JI1lL11gK

A SktletDnoftfleextemal nose I.J!ft lmral view. The skeleton of the nose is compDSed of bone, arti· lage, and connectfn tlssue.IU upper portion b bony and frequently ln· wived lr1 mldfidil fractures. while Its lower. distil portion Is cartlligl· nous ~nd therefore more elil!tlc ~nd less susapabletlllnjury. The proxl· mal lower portion af the naroils (alile) is compo$td of connective ti5sue with small embedded pieces qf cartllige. The lateral nasal cartilage Is a wlr~gnlce litl!ril expansion of the eirtllaglnous Nnl septum r.ttlterthan a sepi!rate piece of cartilage.

B N1111l urrJiage

lnferiarview. Viewed fn:lm belaw, e.achof the majoralarc.artilages is seen to consist af <1 medial and latEral crus. Thls view aiJO dl~plays the two nares, 'Which open lrlto !he Nsal CiiVltfes. The rfghtilrld left nasal cavities ane Sl!l)armd by tile nasal septum, whose Inferior cartilaginous port1or1 is just visible in thediilgram. Thew.rll structure afa single nilllal c;Mtywill be described In this ur11t. and the relatlonshlp of the nasal Cil\'ltytothe par<~Nsal sinuses wlll be explored lr1 the next unit

Elt1mold

bane

Sphenoid bane

Majoraar c.JI1lL11ge

Plllltfnebane

c

BonM of the llltmiiWllll aftfle rTght n.~~o~l cntty I.J!ft latl!ral view. The lateral wall of the right nasal cavity is fllrmed by

slx bones: the mi!XIIIa. nasal bone, ethmoid bor~e. Inferior nasal concha, Pilatlr~e bone. and sphenoid bone. Of the nasal concha. only the lnfe· rlor Is .a sep.;~r.ate bone; the middle .md superfor conchae are pi!rts ofthe ethmoid bone.

18

D Banes of tfle na~~l septum Parasagittal section. The nas.1l septum is fllrmed by tile following bones: the nanl bone (rwf af the septum). ethmoid bone, vomer. sphenoid bone. Pilatlr~e bor~e, and rNxllla. The latter three contribute only small bony pro}eciSons to the nasal septum.

HeGtl - - I. OVnJGI Bones

Antafor

Superior meatus

AM~r~l----~---~

apert!Jre

Pb!rygold PI'OCHS, mecllal plaiJ!

Inferior meatus

Middle concha (ethmoid bone)

E l.iltel'lll Willi ofthe rtght n..-.1 catty Medlallltew. Air enters the bony nas.1l avlty through the inteffor nas.1l aperture and travels th~gh the three nas.1l pass.ages: the supe!'for me-

it:Us, middle meitus, and Inferior meatus. Air le;rve:s the nose through the chOin<~e,. enterlng the nasopharynx. The three niSi I pasS<~ges ue separated Into meatuses by the lnfenor, middle, and superior conchae.

-----------Sphenoid ,(ni.IS

~mddbon~------~~----­

pe~pendlalar pi~

.....:;;iiiii::"~--TriP:....;.;._,'----

Sphenoid

crest

Ma)or~lar

c.rillge,

medlalcna

F N111118lseptum

J>.arasagittal section viewed from the left side. The left lateral wall aftne nas.1l cavity has been removed with the adjacent bones. The nasal sep· tum canststs of ifl anterior car111aglfiOUS part,. the septal cartilage. ind a postl!rlor bony part (see D). The postl!rlor proceu of the car111aglno~

septumextendsdeeplfltothebonyseptum.DeYiatlonsofthenasilsepl:lJm are common and may irMIIve ttre cartilaginous partafttre septum, the bony part. or both. C..5eS In which the septal deviation Is sufficient to cause obstructlor1 of r~aS<~I breattrlng an be surgle<~lly corrected.

19

'· Cranlol Bones

Hftld -

1.10

Nose:

Paranasal Sinuses Fronul sinus

Mullllry sinus

•

b

ElhmGil Cl!lls

MM.IIory

Sphmd

nna

siNJS

A Projedkln of the J11111nlulllnuses oniD the skull • Anterior b lm:ral vi-. The paranilsal sinuses 1re alr-fllled CiYltles that reduce the weight of the skull. Because they ire subject to lnfl3mmltfon that may cause pain CMr the a!Rcted sinus (e.g.. frontal headiche due to frontal slnusltb), knowing the locltfon of the sinuses Is helpful In making the correct diagnosis.

vi-.

a Pni!UIIIt!HifDII rJI the mulllary •nd fnlnblthllel Anll:rior view. The front<JI and maxill'ry sinuses dMop gradually durIng the course of CJ11nlil growth (pneumitlutlon)-unllke the ethmoid sinuses, which ire aii'NIIy pneumatized .at birth. As i result, sinusitis In chUd ren Is most likely to lnwlve the ethmoid cells (with risk of orbita I penetration: red, swollen eye; see D).

Ant1:1tar cr.~ri•l'-•

Cutedge
Sclhonoil >ln~s ScJhonoPi'lallne fwimtn

----lt:=-- - Bodyof sphmd bane

u~~--~~--~----~~ pnxeB

Fronliol

Cutedg!Gtmlddlo n...J mncha {etlvnald bone)

C l..literal-11 rJI the right n...l ciiVIty Midline section vi~ from the lfft with the nilSal conchae~ moved to dlspl~ the openings of the ni1Sobicr1mal duct ;md parilliSill sinuses Into the nasal c.avtty (see colored arrows In It: red • NsolaalrN I

1, b

duct, ydlow • frvntal sinus, orange • mulllary sinus, green • antaior ilnd posterb ethmoid cells, blue- sphenoid sinus: drilfnage routes are destnbed in F).

20

b

Head - - I. OVnJGI Bones

frantll

OfK.a

Anterfar --__ cr.tnlalfosn

mur.

gall

,-_- --_

·~!-'·

Etllmold bone, artltal plm

(

'1---..___ ~ Olllumof

! _ ---r--_ mullloryslnus

r-_

~ ·

.J D Bo11111tn1ctur.ofthe INI~hlnuMJ Anterforvlew. The cen!r.llstructure of the patl!llOSG/ s.tnw:ts Is lfle elhmold bone (red). ItS cribriform pl;tte !Wms a portion of the anterior skull base. The frontal and maxlllaryslnuses are grouped around lfle ethmoid bone. The lnfe· rlor, mlddleand supe!'formeatuses an belden· tified within the niiS
NIMI

Inferior

Milldllorysnur.

P
II!;try sinus 05tlum Is the ethmoid bulla, ~h:h cont.11ns the middle etftmold cells. At Its iflte. rfor mll~ln Is a bony hook. lfle uncinate proa!$$, ~ich bounds tne mill011ary sinus ostium anteriorly. The middle concha Is a useful land· marie In surgle<~l procedures on the maxillary sln~a lind anterior elhmold. The lateral wall separ;rting the ethmoid bone from the orbit is the paper-thin orbital pl
E Nulll caMty lind plnlllnllnl strues

Transverse section viewed from above. The mucosal surface anii!Zimy has been left Intact to ~- ~~- narrow the nasal passages a~ Even relattvdy mild swelling of the mucosa may obstruct the nasal cavity, Impeding aeratlofl oflfle parana sal sinuses. This diill!lr;~m abo shows that the pituit.1ry gland, loc<1ted behind the sphenoid sinus In !he ll)pophyseal fossa (see C), Is il~slble to transnasal su~le<~l procedures.

fnx1tllslnus

F Sites wflere the nasoiMrlrNI duct and par~~~r-.JIIInuMJ optn Into die.._

.....

Unc'him!proaw

Nasa!G!Mty

SlnlcluNt tMt .....

lntDthe--.. • Nasolaatmal duct

Mlddeoantha

mtl~Ws

Middle

meatus

SUpeflor

• • • •

fnlnulslnus Milldllarystnus Anterior ethmoid cells Mlddlt elhmold cells

•

~lforethmold aells

~~~Cj)l~m

tnfu'lor c~uha

mel!Ws Sphen~

elllmold reoess

• Sphenoid sinus

-

Ci O:IUomtatlll unttorttheleftskluftM Coror~al

section. Wilen the mucosa (dilated epithelium) lr1 lfle ethmoid cells (green) becomes swollen due to Inflammation (sinusitir.), it blades tfle flow of.secretions (see arnowl) from the front<~l slr~us (yellow) and maxillary sln~a (orange) In lfle ostlomeat<~l unit (red). Because of tflls blockage, mkroresplr.~tory

organisms also become trapped 1r11fle other sinuses, where lfley may incite an inflammallofl. Thus. while the anatomle<~l focus of the dlse<~se lies lr1 the etilmold cells,lnflammatory symptoms are also manlti!sted In the front.ll and maxillary sinLIIes. In patients with cl!ronic 5lnusltts, the narrow sites e<~n be surgle<~llywf~ ened to establish an effecUve drainage routr. !hereby curing lfle disease.

21

Hftld -

'· Cranlol Bones

1.11

Temporal Bone

A l'lllltlonofthetemlloralbone lnthesbll l.eftliltlerillvlew. Thetemporal bone Is a major component: of the base of the slcull ltfonns the capsule for the auditory and Witlbulilr .app.arilll:us and bnrs the articular fum of the temporomandibular joint. --"'='"""=--=~-Temporal

bono

,...

_......:;4--- tblldlbulilr - - - ------:F--- !iq........... part p;ort

-.. p;ort

Tymp;onk-........;~~~

p;ort

• B Olllflcdon cet*rs of the left temporal bone Left: latJeral vh:w, II Inferior view.

The mmpor.al bone develops from three cenll!rs thilll: fuse tD folm .a single bone:

• The petrous p.art. or petrous bone (paleglftl'l), contains the auditory and ~bular app.aratus. • Thetymp.anlc p.art (dariatr green) forms large porUons of the external iiUditDry canal.

• The sqUimous part. or temporal squlmil (light green), bears the articular foss.~ of the temporomilndlbular joint (ll\ilndlbular fusu).

Noll': The styluid pllllteSs appurs tD belong to the tymp.anlc part of the ll!mporal bone because of ItS location. Dewlopmentally, hDWeW!r, It Is

il

partvi the petrous bone.

Ounfil

tymp.onl

'l)rmpa-1k--~

""'mb.,ne Ph•ryng~rlc

(•udiiDry) tube

22

l'icl111 norve

Matdd olr Cll!ls

c Pro)edlan of dlnlc.ally fmporbnt ltluclures antD the left tllmponiiKin• The tymp.anlc membrane Is shown tnnsluamt In this lilll:er.al view. Because the petroU5 bone c:ontains the middle and inner ear and the tympanic membrane, a knowledge of Its anilll:omy Is of key Importance In otological surgery. The lntemil surface of the petrous bone hils openings (see D) for the panage of the filcii I nerve, inll!rnill carotid illt!:ry, ;md lnll!rnal jugulu vein. A nne nerve, the d1ordi tympani, passes through the tympanic amy, and lies medial tD the tymp.anic membrane. The chorda tympani artses from the facial nerve, which Is susceptible tD Injury d urtng surgical procedures (see C. p. 79). The mastoid pnKeSS of the petrous bone fonns air-filled cl1ambers, the mastoid cells, that vary gr5tly In size. Becau:~e these chambers c:ommunlcall!wlth the middle ear, which In tum c:ommu nlcatti wtth the n.asop~rynx viii the philryngotympanlc (au.dltDry) tu.be (al.so called Eustachlin tube) bacteria In the n.asopharynx m.y pass up the pharyngotympanlc tube and g;~in aca" to the middle"'· From the.re they m41Y p;qs to the mastoid air cells and flnally enter the tr.nlal UYlty, causing meningitis.

HeGtl - - I. OVnJGI Bones

x---=---==--=-----;;~~~~~-£mmal

llalUS11c: opening

..=;~--MISIJlld

frmmen

•

Styloid

=-- --4-- - - Altlculn tlbefde

PI'Xle.SS

- -11=!--- -

lll~ndlbul;lt

fossa .,..., __

£mm.1l liCDUStlc opening

- - --rl--- for.men lllastcld

D Lcfttt=mponlbone liltl!r.lllllew. The prlnclp;tl structiJres of the temporal bone ire Ia· beled In !he diagram. An emrss.uyveln (seep. 9) p;tsses lhrough the mastoid foramen (extl!rnal cnifia! shown ir1 a, intl!rnal orifia! in c), 01nd the chordiltymp;tnl passes lhrough the medlill part of!he petro· tympanic fissure (see p.147). The nnistold process develops graduilly In life due to trutlon from the sternodeklornastold muscle and Is pneumatized f'rDm the inside (see C). b lnh!rtor'lltew. The shitllow irtlaJiar fos.sa of the temporomindlbular joint (the mindlbularfossa) Is deirlyseen from !he Inferior view. The fac:lal nerve emerges from the b.ase of the slculllh~h !he stylo·

;a

mastoid for01men. The Initial part of the Internal jugulilr vein Is .. ~ herent to the jugular fossa, and the lntemil carotid 01rtery passes lhrough the Cilrotld Cinal to enttr the skull. c Medlallllew. This Yii!Wclisplays the internal orifice of the ma.stDid f~ ramen and the Internal at1lustlc meatus. The f.lclal nave and vestlbulooochleilr nerve are among the struc!IJres that p;tss through the Internal meatus to enter the petrous bone. The part of !he petn:MlS bone shown here is also called the petrous pyromid, whose apex (of· ten cillled the "petrous apex.") lies on the Interior of the b.ase of the skull.

23

Head - - 1. CmtifJI Bones

1.12

Sphenoid Bone

hlatfnebone

fl1l0till bone

Sphenoid Sptlenold bone

VOmer

Ocdpllll bone

T81110nll bone

bon~

Ocdpltal bone

Tmpcnl bone

P.Jrtetalbone

A PosiUon ofthuphl!tlold bonelntflullull

The sphenoid bone is the most struttur.~llycomplex bone in the hum~n body. It must be vlewed from wrlous aspects In order to appredate all Its fe.rtures (see also B): ;a I.JI:e of the skull,

external ;aspect. The sphenoid bone combines

With the occipital bone to fonn the load-beartng midline strutture of

the skull base. b . _ of the skul, ln'lllmal iiiPKt. The sphenoid bone fomu the

boundary between the anterior and middle cranial fossae. The openIngs for the passage of nerves and vessels are dearly displayed (see details in B). c; ~1111-. Portions of the great\!r wing of the sphenoid bone can be seen above the zygomatic arch. and portions oftile ptef)'gold process can be seen below the zygomatic .arch. lllo!l!the bones that border on tile sphenoid bone In eKh VIew.

B llollrtitd sphenoid bDne

lnlintor ~~~-(Its position In situ Is shown In A). This VIew demon· strates the medial and latl!l"al plates of the pterygoid process. Be· tween them Is tile ptsygold fossa, which Is oc;cupled by the medial pterygoid muKie. The for.lmen spinosum ;nd foramen not\Jndum provide pa'dlways through the base of the skull (see als;o Inc;). b Antl!t1'or llfew. This VIew Illustrates why tile sphenoid bone w.~s orfg· ln.ally called the sphecold bone (•wasp bone") before a transafp· tion em:w turned it into the sphenoid ("wedge-shaped") bone. The apertures of the sphenoid sinus on each side resemble the eyes of the wasp. and the ptsygold processes oftile sphenoid bone fonn Its dangling legs. between 'Which are the pterygoid fossae. Thfs111ew .also displays lfle superior ortlital fissul'l!, 'Which amnects the middle era· nlal fossa with the orfllt on each 31de. The two sphenoid sinuses are separated by an ln!l!malseptum(see p.21).

;a

24

Sphenoid -..,.::..-~~=' bone,

g!Nter -..fng

Temporal c

bone

c Supedar W!w. The superior view displays the sella turcica, whose central depression, the hypophyseal fossa. contains the pituitary gland. The foramen splnosum. for.~men ovale. and foramen rotundum can be Identified posteriorly. d Plllterklrllfew. The superior orbital fissure is seen particularlyclealfy In thlJ Ylew, while the optic canalis almost completely obKured by the an!l!rtorclfnold process. The foramen rotundum Is open from the middle aanfal fossa to the external b-ase of tile skull (the foramen spinasum is not visible in lflis view; compare with a). Because the sphenoid and ocdpttal bones fuse togelfler during puberty ("tribasllar bone•). a suture Is no longer present between the two bones. The cancellous trabeculae are exposed and have a porous .appearance.

Head-- 1. CmtifJIBones

1.13

Occipital Bone and Ethmoid Bones

~totlanofthe GCqlltal bone llntotfluxtl!lnal bale of the dalll lnferlorvlew. NoU>the relationship ofthe ocdpltal bone w the adjacent bones. The ocdplt.ill bone fuses ~th the sphenoid bone during pubertytoform tne •bib
A

Jugularpn:aD

Foramen

magnum ~n~ar--~~-----­

c:anal

-----=.;...~~~--~------~--~

lnfu!or

nuchal line

oalp!l
foramen ------':it-"i:--~~-m~V~um

•

Superior

Supnme

nuo:hallkle

nuthllllne

B llolltltd outpltal bone <11

lnlilrior W.W. This view shOW51fle basilar p;rrt of 1he ocdpttal bone. whose anterior portion Is fused to the sphenoid bone. Thecondylarca· nal temllnates posterior to the occTpltll condyles, while the hypoglos· s.al canal passes superior to the aa:ipil:lll ctJndy!es. The ctJndy!arcanal lsavenousdrannelthatbeglnslntheslgmoldslnus;rndendslntheocdplt.ill vein (emlswry vern. seep. 9). The hypogloswl canal cont;rlns a venous plexus In
26

b tat l~ttnl W!w. The extent of tne oa:ipit.ill squama, which lie$
HeGtl - - I. OVnJGI Bones

C lntlefriltlon of the ethmoid bone Into the lntem~l biiSe of the

D lnleil'illtkln of the ethmoid bor~e Into the f.ld~lskeletlln Anterior 1/few. The elhrnold bone Is tile central bone of !he nose and

skull

Superior view. The upper partion of the etnmoid b~ne forms p~rtaftne ~nrerior aanl~l foss~. wfllle Its lower pmlons contribute structur;llly to tne naiNII cavities. The ethmoid bone Is bordered by tne front;rl ;md sphenoid bones.

paran;~wl~nusu.

1-+r-"T'':--:-'---

Su~r

meatus

C~ga!ll---

Anterfor ethmoid foramen

..l

- •

elllmold ~ for.rnen

llostetfor

'

•

Olbltll plate

Middle

c

d

concha

Leftloltar~~hltew. Vle>Mngthe bone from tile left slde, we observe the

E lllolmdethmoldbone

c

;a SUpertor lllew. This view demonstr.ttes tne afrta gall!, which gives

perpendkular plate and the opened anterior ethmoid cells. The orbit Is separated from the ethmoid cells by a tilln sheet of bone called the orbital plate. d Posteliorlll-. Th!s Is the only view ~flit displays the undn;~te process. which Is almost completely covered by tile middle concha when In situ. It partially occludes the entrance to tile maxillary sinus, the semilunar hiatus, and it is an important landmark during endOSa:Jpic surgery of the m;~1dllary sinus. The narrow depression between the middle coocha and undnm process Is ailed tile ethmoid Infundibulum. The frontal sinus, maxillary sinus, .and ;mterfor ethmoid cells open into ttl is "funMI." The superior concha is located at the~ nor end ofthe etflrnold bone.

al:t.ichment to the falx cerebrt (see p. 188) .md the hoiUolrtally dl· rected cribriform pl;!te. It is perfor;ated by fur;amina ttl rough which theolf.lctoryflbers pass from the nawl c:.Mty Into tfle anterior aanlal fossa. With Its numerous foramina, !he cribriform plate Is a mechanl· ally weak structure that fractures easily rn response mlriluma. Th~ type of fracture is m;~nifestl!d clinically by cerebrospinal fluid leabge from the nose ("runny nose" In a pMientwltfl head Injury). b Antl!ffor VIew. The anrerior view displays the midline structure !:hit separ.ltles the two nasal cavities: the perpendicular platl! (which resembles tne pendulum of a grandf.ather clock). Nob! also the middle concha. which !s partoftheethmold bone (oftfle conchae. only the lnferfor concha Is a separate bone), and tne ethmoid cells, which are dusttred on bolh sides afthe middle conchae.

Hftld - - 1. c:nmlallona

1.14

Hard Palate

MIXIIIo MDIlory stn~a

Pilatlne

bone Sphonaid bone

• A lntegr.Uon of the hlrd p1!m lntllthe lillie afthulcull. Infertor view.

MDIILio Ch~e

Sphtneld bono

Palltlne bone

Vllm•

I . . _ afth• lard plliltll • SupertDrwlew. The hard ~lm Is a hortmn-

ul bony plate formed by ~Its of the miXrna and ~LioUne bone.ltsetWs as a ~rtltlon bebm!n the orill ilnd nasal cNtles. In thls vttwwure loolc:lng down at the ftoor ofthe nasal Cilvtty, whose lnft!rlor surface fonru the roof of the o~l c.wlty. The upPfl' porUon of the rNxllla has been ranO'ied. The palilltlne bone Is bordered postlflor1y by the sphenoid bone. b Jnfe.tor view. The choanae, the posterior openlng5 of the niiHI cavity, begin at the postet1or border ofthe hard palate. c Obllqua poltllrlor This view demonstrat:es the dose relaUonshlp between the o~land nasal cavities. Nom how the pyramidal process ofthe ~Iatine bone Is Integ rated Into the later
vi-.

Middle a>ndla ChC11111e

Sphorloid bone

'

28

1/cmer

Head - - J. CranlaiBones

lndslw -

-....,..:!.11---

anal

c

Hlrdp~l.-

1

Superior~~~- of the floor of the Nsal c-

ity (• upper portion of hard palate) with the upper put ofthe maxilla rei!IIJiofed. The hard

-l!.y -----::;5::; sl-

"hnswrse

palate~r--stheoralavttyfmrnthena­

Poi.Unr~.

-~----::!~~-~,.,_::c....__

perpondla.olor ~

poliltlne>ubn

G - r ----;;:-...~ pallllnec.ool

I

lndslvo ----~~~-...:,V an•l

r ...n....,.

defectln~ngthellp.alveolus,andpalm).

- - . . -.........--l'ilotil~prote$$ of111111dlo

Nom: the Nsal cavtty (whose floor Is formed

by the hilrd palate) communicates with the nuophal)'llll by VRY of the choilnae.

',-----,-:------'~~~~-Medon

pohrtlnuulun!

paiiiiMIU!il"'

4:

G-r pol.une furomon

lnfa1or ---~ orbit!Iftlsu"'

Ar*rtor dilold PfOaSil

O•tllmaf sphenoid sinus

wl cavities. The small a nal that linb the or.J and Nnl CMIIIies, the Incisive anill (present here on bolh sides), merges within the bonewform one canal. whim opens on the lnfertor sulface by a single ollllce. the indsi~ foramen (see b). b lnfef1Dr VI-. The l't¥0 horizontal processes of the mullla, the palnfne processes, grow t.Jgdher during development and become fused at the median palatine suture. Failure oflflis fusion results in a c/
-;t:=:::-----.,.!;fi-.411'~11fl'i

ObllqiMI ,_.lior vi- of the posterior part of the sphenoid bone at the level of the sphenoid body, displaying bolh sphenoid sinuses separated by il septum. The dose tGpographlul relationship between the nasal cavity ~nd hard palm can be itpprec:lated In this vtew. If the hard palm Is unfused in a nursing infant due to a cleft anom~~ly (see It), some of the Ingested milk w111 be dr-ted from the oral cavity and will entwthe nose. This defect should be dosed with a plate lmmedlatdy a~r birth tG permit SiltlsfactGJY oral nlll1ttfon.

Optic C
- - - - - - ' : - - - Supi!I1Gr orbltll ftuure Middle Cll'lchi

Pb!rygald

fOSM

..

Inferior --~~===~ orblbol lilsun!

Ethmoid bane, ~lcullrplote

O.O.na

Medlin - -----.;=:: polilt1u.Jtun!

c

Polillne proooosof111111dlo

29

Head-- 1. CmtifJIBones

Mandible and Hyoid Bone

1.15

R;Jmus afm~ndlble

~r--~------~ p;lrtaf

mandble

lloct;af mandble

•

proc:KS M1ndlbular foramen

--i-----,. b

llilmus

of mandible

Oblique

c

tne

A Mindlble

a Alltl!rlor ww. The mandible Is connected to !he lllscerocr<mlum at the temporomandibular jaint, whose convex surface is the he
the mandlbularoondyle. This "hN
30

b Posterior ww. The mandibular foramen Is particularly wdl dis· played In this1/few.lttransmrtsthe Inferior alveolar nerve, wltlch supplieuensory innervation to the mandibulartnth.IU temninal branch anergesfromthe mentalforamen. The twa mandlbularforamlna are Interconnected by the mandibular c:.1nal. c Oblique left lltel'll ww. This 11tew displays the coronoid process, the condylar process, .ilnd the mandibular notch between them. The coronoid process Is a site for muscular attachmmu. while the oondylarprocessbe.ilrslhehudofthemandlble,wltlchartlculateswlththe mandibular fossa of the tempor.ill bone. A depre.sslon on the medial side of the carldylar process, the pterygoid f\wea, givu attachment to portions of the lmral pterygoid muscle.

Head - - J. Cranial Bones

•

c

8 Age-nilmld dlanga., themindlble The strudure af the mandible Is greatly lnflul!llced by the alveolar processeJ of the teeth. Because the angle of the mandible adapts to changes In the ;alveoli r process, the angle betvMen the body and ramus also varies with aQe-mated chingu in the dentition. The angle measures ipproxlmately 150' it birth, ;and approxlmatdy 120-130" In adults. cleaNsing to 140" In the edentulous mandible of old age. • M birth the mandible is without teeth and the alveolar pgrt has not

yet formed. II In dlllchn the mandible burs the deciduous teeth. The alveolilr part is nill maMiy poorly d~ed beause the deciduous teeth lire considerablysmllller thin the perminent teeth.

Lesoorhom

•

Gnntrham

c In adults the mindlble be<~rs the permanent teeth, and the lllveolar

part of the bone Is fully d-loped. II Old ill" b c:hilrarnrized by an edentulous mandible with resorption of the ;alveoli r process.

Nom: the resorption afthe alveol;ar process with advanced ;age leids tD a dJ~geinthe~itionofthementalforamen(whidJisnorm;~llylocated

bel- the secGnd premolllr tooth, as In c). This !Nnge mmt be tlllcen ini:D account in surgery or dissections iiMIIving the mental netw.

l..ftJerham

G.-hom

Body

Cireollor ham

c C Hyglclbone

a Anterior vtew, II posterior view, c oblique left l~ter.~l view. The hyoid bone Is suspended by muscles between the oral floor and Ill 'l"'X In the neck. although It Is Usted among the cranllll bones In the Tmnlnolog.lo

Anolomla!. The greater hom and b..!y afthe hyoid bone are palpable In the neck. The physiological movement of the hyoid bone dur1ng SWill· lowing Is also palpable.

31

Head-- 1. CmtifJIBones

1.16

Temporomandibular joint

Zygomrtfcp- - -

oftl!mponlbone Petrotymp;~nlc

---:.:....._ __

fluure

A Mindlbul;n foa.1 of the tamporvm;mdlbulu!oint lnferlorvlew. The head of!he marldlble artkula!l!s wlt:h the marldlbular fossa In the temporomandibular Joint. Tbe mandlbularfossa Is .a depres-

sion in the $CJu;rmous p;~rt of the temporal bone. The articular tuberde Is loc.m!d on the anterior side of the marldlbular fo$$a. The head of the marldlble (see B) Is marki!dly smaller than the mandibular fossa, allow-

lng It to NYe an ;ulequ;r!l! range of movemmt (seep. 35). Unlike olfler irtlallar surfaces. Ule mindlbular fossa Is C<M!Il!d by flbroe<~rtllage rithertban hyillnecartllage. As a result, It Is not .as dearly delineated on the skull ;~s other artiallar surfaces. The external auditory canal lies jus;t behind the marldlbular fossa. This pi'Oldmlty explains whytrauma to the mandible may damage the auditory canal.

Hmdof mandible

Neck of

mandble

Ulgula \r-f- - 1111ndlbular foramen

• B Head ofthe m.~ndlble In the rfght tl!mporvmlndlbul•r Joint a Anterior view. b posterior view. The head ofthe marldibleisnotonly marbdlysmaller than the artlcularfossa but aiJO has a cylindrical shape. This shape further lnaea1es the mobility of the mandibular he
32

c

llglments of the lefttl!mpororn~~..joTnt Lateral view. The temporomandibular joint is surrounded by a relatiw.ly lal!.e<~psule, which pemntts physiological dislocation durfngjawopenlng. The joint Is stiblllzecl by three ligaments (see c ;md D). This la!l!r.~l view demonstr.rtes the strongest of these ligaments, Ule la!l!r.1l ligament. which stretches t:M!I' the capsule and is blended with it. The weab!r stylomandibular ligament Is also shown.

HeGtl - - I. OVnJGI Bones

i'tA!tygospnous

Artla.l~r

l1111rnent

dsk

Millldbular

Jolrt

nolth

Glp$Uie

Sphenornand~

Headd

mar.dlbl~

bular ligament

D Right tlmpoi'Omilrldlbulilrjo~ilnd lgiiiFMII'Is Medial view. The sphenomandibular ligament c:<~l'l ilso be ldenUfled In thlsvlew.

E Openld 11fttllmporomilndlbulilr Joint Lateral view. The c:<~psule extends postertorly to !he petrotympanic fissure (not shown here). Interposed betweel'l the mandibular he
F Dlsloalt.lon oftfle tempcii'Omlndlbullr Joint The he
G Sensory rnnerviUCin of the tl!mporomandl'bularjol'nt capsule (afterSchmiclt) Superior view. The temporomandibular joint apsule IJ supplied by articular branches arlsll'lg from Utree branches ofthe mandibular dlvlslol'l af!he trfgemlr~al nerve (o.t V

v:

• Auriculotemporal nerve • Deeptl!mporalnerve • Masseteric nerve

33

Head-- 1. CmtifJIBones

1.17

Temporomandibular joint. Biomechanics

lr.lni\'I!IV lllls throug. 1

headdmarldble (axisofrct.ltlan)

--~. ..l·- y '\J

I l { ....,.

150'

I i I

Headd

I' 7.

f.

i

I

A.

,

f

I

r.r

•

b

Woriclng s16e (~on)

c

A Moftmenb of the 1111ndlble In thetanporom~ndlbullr )olflt Superior view. Mostofthemovemerns In the temporomandibularjoint are complex motions that have three main components: • Rotitfon (openlfl!l and dosing the mouth) • ll'anslatiOn (pl\ltruslon and retiUSion of!he mandible) • Grinding movemenU during mastitlation

a

t~Gtatian. The axis for joint l\ltation runs tran~e!y through beth heads of!he mandible. The two~ Intersect at an angle of approxl· mate!y 150' (range of 110-1800 betwHn lndMduals). Durlr~g this m011e1111ent the temporomandibular joint acts as a hinge joint (ab· ductionfdepression and addLJCtianJelevation of the mandible). In hu· m;ms, pure rotOitlon In the temporomandibular joint usually ocaJrs only during sleep wtth the mouth slightly open (apenure angle up to .ilpproxlmately 15', see Bb). When the mouth Is opened past 15', rotation is rombined with translation (gliding) of the mandibular head.

34

b Thlnslltton.ln this mcMrnentthe mandible ls adwnced (pi'Gtl'Uded) ;md retracted (retruded). The axa for this movement are parallel to the median axes through the C4!11ter of the mandibular heads. c Crtndlng mowments In the left tl!mparam1ndlbular Joint. In describing these laterai~T~~Mments, a distinction Is made between the 'resting condyle" arid the 'swinging condyle." The restlfl!l condyle on tile left working side rotates .ilbout;m .almost vertical .axis through the head of tf1e mandible (also a rotational axis). while the swingIng coneyle on the right bolla riCe side swlr~gs forward and lnWilfd In a troarulatlonal ITI<M!ment. The lilteral excursion of !he mandible Is measured In degrees .ilrld 'Is called the Bennett .ilngle. Durl'ng this movement the mandible mCIIIC$ in laterotrusion on the working side and In medlotruslon on the balance side. d Crtndlnl ~ents In the rlflht tl!mporornand111ular )oint. Here. the rfght temporomandlbul.arJoint Is the worlclng side. The rtght resting condyle rotates about an almost 111!rtic;al axis, while the left eo& dyle on the balance side swings forw.~rd and Inward.

HeGtl - - I. OVnJGI Bones

Articular tlb«de Mlndbular!Wsa

"· .~'~..-::;~"ioo-- Artlcll~rdlSk ~)J;J;R--- Hudc:lmandble jclnt capsule

l.lrtefll pterygoid m~DCie.

lnftr!orpalt

•

Mf(ulardllk Ht.lid of mancllble '/fiJ_.._ _ joint (4)51.fe

..........._ .,. ftC'

lara! ptelygcld musde,

Wi!rforp.n

8 Movemllllltl ofthe tl!mporom~ndlbuln Joint 1St later.illllfew. E.ilch dr.ii!M'ng shows the left temporomandibularjoint iocluding the articular dislc .ilnd apsule and the later.al pterygoid mus· de, and e9Ch schematic dlilgram ~t right shows the correJpondlng
b Mouth opened to 15'. Up to 15• of.ilbductlon, the head of the ttlilndlble remains In the mandlbularfosS.il. c Mautfl opened p111t 15'. At this point the hl!>ld af the mandible glides forw.lrd onto the articular tubercle. The joint illds that runs transwnely through the mandibular head Is shifted fotwilrd. The artlculardlsklspulledforwardbythe supertorpartofthe lateral pterygoid musde,. and the head of the mandible is drawn forward by the lnfmorpartofthatmusde.

35

Head-- 1. CmtifJIBones

1.18

The Teeth in situ

Nl!dc

}~

}A Principii partsofthetDDtfl • CnMn

• Nedc • Root

I Penn;ment teeth of;m ildult a Malia. Inferior lllew displaying the ocdu· s.1l sul'fac:g of thetl!eth. b M;mdlbll. Superior lllew. ~ch

tooth is given an identifiCJtion code (see p. 38) tD describe the spedflc loc.rtfon of dental lesions such .u arfes. ~ch half of the maxilla and mandible a~ntains

the following set of anterior ;md posterior

(poslcinlne) teeth: • Anterior teeth: two lndsors ;md one canine tooth. • Po:ltl!rlor ll!eth: two premolars and three

mola!'l.

lnclsart

b

36

Head - - I. OVnJGI Bones

c

b

C Ocd.tsal pl1nund dental an:her. "· b '!WH oft.th ~nd the ocdUMI pllne. The miUdlla and mandible present a symmetrk31 arr.;mgernent. With the moutil dosed (ocdw.ill position), the maxillary teeth are .ilpposed to their mandibular counb!tpatts. They are offiet relative to one another so that the cusps of one tooth flt Into the flssureJ of the two opposing teeth (cusp-and· fissure dentition). Ikeause of this arr.-mgement. every tooth comes Into contact With two opposing teeth. Tills offset results from the slightly gne.ilb!r width of the milleillary incisors (seep. 39). The ocdu· Jal plane often fomnJ a Juperiorlyopen arch (von Spee curw). c Dentllerches. The teeth of the INX!IIa (green) .ilnd marwllble (blue) are arr.anged In superior and Inferior.ilrche.s. The superior dent.al arch fonns a semi-ellipse while the inh!rioc- arch is $~\;aped li~ a p;~rabola.

---Enamel

~

SllarpeyAbers

---

Allltdarw.~ll

~ f}{t - -, '

'

Cementum

E Supportklg 1tn1cturu of the tDotfl: the periodontium The tooth Is .ilfldlored rn the .illlleolus by a special type of syndesmosis ailed a gomphosis. The tissues th.ilt imrest arid support the moth, the periodontium, com!Jt of: • • • •

The periodontal ligament The cementum Thea!Yeolarwall The gingiva.

The Sharpeyflbers .are collagenous fibers that p;~ss obliquely downward from the allll!olar bone and insert into the amentum of the tooth. Thil> downward obliquity of the fibers transforms mastk:atlxy pressures on the dental arch Into tensile stresses acting on the flbefs and anchored bone (pressure would lead to bony <~trophy).

D HhltoiDgy af I tDotfl

F Cl:lnnec'.tM tissue flbln In tile gingiva

lllustr<~ted

Many of the tough collagenous flber bundln In the connect!-tlssue core of the gingiva above the alveolar bone are arranged In a screw-Uice pilttem around the tooth, further strtngthenlng Its attachment.

here for a mandibular !ndsor. This diagram shows the hard tissues of the tooth (enamel. dentine. cementum) as well as the soft tis· sues (dental pcJip}.

37

Hftld - - 1. c:nmlallona

1.19

Permanent Teeth and the Dental Panoramic Tomogram

A Coding dJejM!II'IIIInenttHth In the United States, the permanent t:Hth are numbered sequentially mher than bdng aulgned to qUidrants. Progressing In a dockwlse fashion (from the perspecive of the viewer), the b!l!th of the upper arc

are numbered 1 to 16, while thwe of the lowtr are considered 17 to 32. Note: The tnird upper molar (wisdGm tooth) on the patient's right

Is considered 1.

----Meslllll

Bue<.ai--

-

B Detlg..UOn af tDath IU!'fllc:es Superior view of the ma ndlbular dental arch. These designations ilre used In describing tne precise location of smilll carious lesions. The tenn krbla/ls used for Inelson and canine teeth,and buccoJ Is used fur premolar and molar teeth. The t.tm lln9ual Is used far the mandibular teeth and pa/atolfor the m~llary teeth.

38

- - Ungual (Pilatal)

Head - - I. OVnJGIBones

32

--4-~""-

lhnlmclar (wisdom tooth)

28

c

27

26

25

Dl!ntll panoramktDmogn~m

The dental panoramic tomogr.~m (DPT) Is <1 survey radlogr<~ph that al· lows a prelrmlnary <~~e~ment of the t:emporoiTiilndlbular joints. miiX· lllary sinuses, maxllloiTiilndlbular bone, and dental status (c.1rtous le· sioru, location of the wisdom tzeth). It is based or'l the principle of con· vent!oBaltomographylnwhlchtheX·raytube;mdfllmaremovedabout the plane of Interest to blur out the shadows of structures olltS!de the sectional plane. The plane of Interest In the OPT Is shaped like a parab· ola, conforming tD the shape of the jaws. In the case shown here, all four wisdom teeth (third molars) shocJid be mracted: teeth 1, 16, and

17 are not fully erupted and toad\32 is horizontally impacbl!d (cannot erupt). If the OPT r<~lses su~plclon of c<1ries or !WI: disease. It should be followed with spot radiographs so that spedflc regions of Interest can be ev.aluated at higher resolution. {Tomogram courtesy of Prcf. Dr. u. J. Rtlther, directar of the Depart· ment of Diagnostic Radiology, Center for Dentistry and Oromaxlllof.ldal Surgery. Eppenclo!f Un!Yerslty Medical Center. Hamburg. Gennany.) NDIJe; The upper Incisors .are broilderthan tile lower Incisors, le.adrng to a •Cllsp-and-fissure• type of ocdusion (seep. 37).

39

Head-- 1. CmtifJIBones

1.20

Individual Teeth

Oaloml J\lrf.u:e (1--ofthe CITM'II)

.....--...... ublal

Distal

•

•

Distil

Palmi

LiliaI

b

c

I

Labial

UnsJUII

A lnc:hol'$

Centnllrldsor (9); b la!I!AIIrldsor (10): c lower Incisors (23-26; 24
;a

B C.nklcs {Culplds} Upper canloo (11 ): b lower e<~nlr~e (22): • - the tip of the crown. which represents the ocdus.1l surface. The aown Is thlckerme.slallythan distally, and has greater curvature (arrow). lrl dogs, these teeth (also known a$ cuspids or t'Yt' ~th) a~ developed into fangs fDr gripping the prey between the jaw'lo-hence the tam "canine.•

;a

Ocd1.11al

surface

(f) •

Buccal

Dlst.ll

b

Buccal

DISUI

g oa:kls.ll

\1 c

Bucxlll

Distil

C Pranol;us(llcutphfJ) First premolar (1st blalspld. 12); b second premolar (2nd bicuspid, 13); c flrrt premolar(21); d second premolar(20). The premolars l'l!p· resenh transitional fDrm between the incisorsand molars. Like the mo· Iars. they have cusps and fissures Indicating that their primary function Is Ule grfndlng of food. rather than btung and tearfng. The upper left

;a

40

d

Bucxlll

~umo;

Distal

flrst premolar (12, a) Is the only premolar that has two rooa. 113 mesial surface which borders the neighboring proximal tooth often bears <1 small pit that rs difficult to dean and vulr~erable to cartes. The othtfpremolars have one root that is divided by a longitudinal groove and eo& talns two root canals.

Head - - J. Cranial Bones

•

J

luwl

...

OtdUSil ~

..t

J Distil

Pa~l

II

Bu«iiil

.~J Dimll

Ocd....,l

su..U

:J 1'11&.11

Otdusol surface

Ocdusal sumao

c

llucal

luaal

Unguol

D Malilrs

• First malar (6-yr malar, 14); b second molar (12-yr molar, 1S); ' third molar (wlldom tooth. 16): d flrst moln (19); e second molar (18); I third molar (17). Most of the mol1rs hllll! three roots to v.tthstand the greater mastiatory pressures in the molar region. The rOGts ofthethlrd molars {the wlsdomtKth, whld1 erupt.tb!r 16 ~rs ofage,

llu
DINI

Ungual

U~~guol

If it ill) a~ mm monly fused t:ogl!ltl•. pirtlaJ Iarty In the upper ltlln:l molus. Bec<~use the molars aush and grind food, they have a crown wlltl a plilteiu. The !Inures b~ the OISps are a fn!quent site of canes formitlon In idolescants. No~: The term llnguo/ls used for the rna ndlbullr meth. the term polrrtu/ for the mnlllilryteeth.

41

lkfHI - - 1. Cnmlallona

1.21

Deciduous Teeth

loo o

c=,.c:.- -

&months

l)Ur

•

•

c

A Deciduous IMth Dl the left side The deciduous dentition (baby teeth) consists of only 20 teeth. Each of tne four quadrants contains the following teeth:

• Centrillndsor (first Incisor) b !Ae111l incisor(srcond incl- )

c unlne (aJSpld) d First molu (6-yr molar) 1 Se<:ond molar (12~ molar) To dlstfngursh the deC:Iduous tJtetfl from the permanent IMI:h, they are coded with letten. The upper ardlls l11beled A1x1 j, the lowef' Is labeled KtDT(seeD).

I E'ruptlon ofthe tMth The erupljonsofthedeclduouund pamanentteeth are called the first and second dentitions, respec:tlwly. The lndMd u1l teeth are listed from left to r1ght (llf_..s perspectlw) and the types of t2etfl1re ordered

._.

according lxl the time oferuption. nm

l'rP• ofIIOOih

dmiiiiDn

lndMduaiiDOih

Tme of1n1ption

(lee D)

Centrll lncllor l..at2rallncbor nrstmollor Clnlnas Semndmollr

10_.

E.F; P,O

5-8 months

D.C;Q. N

A,J;T,K

8-12months 12-16 months IS-20 months 20-40 months

lndiVldull tvoth

Tlme of eruption

8,1;.5, L C. H: R. M

12J'M"

Secand

'J'rpe of IIOOih

(Mep.ll)

dmiiiiDn Firstmollr

l, 14; 30, 1!1

6-BJUrs

Centrll lncllor Ularal lncbor nm premolar Clnine Second prtmollor

6-!IJUrs

Second molar

1,9; 25,24 7, 10;26, 23 5,12: 21,21 6, 11;27,22 4,1);2!1, zo 2. 15;31, 18

Third molar

1. 16;32. 17

(.......... IDOih,

r~mollor1

7-lo,_,. 9-ll)'Urs 9-14years 11- 14yoears 10-14,urs ("12.,.....,..., 16-30)'I!ii'S

c Eruption pdllm Dldw adduoul •nd p.11111nlnttwth (afll!r Meyer)

The eruption pill:tern Is nlus1nlted for the upper left teeth (deciduous tJteth In blade. penna nent tl!eth In red). Knowing the Urnes of eruption of the teeth lsdlnlcallylmportant. illS these diu c1n provide a bulsfor diagnosing growth debys 1n children.

Head - - J. Cranlal&mes

D Coding the dldcluo• tad! The upper right molar Is considered A.. The lettering then proaeds dockwlse <~long the upper arc ind back IITOIIIS the lower. E Denlftlon af 1 5-yuMIIId chftd Anterior view; c, d left lateral view. The

1, b

interior bony plate over the roots of the deciduous teeth h.u been remowd 1D display lfle underlying p~rmiln~nttuGth boos (pelt blue). This age was selected beause iII of lfle deciduous teeth h.ilve erupted by lflls time ind ire ill stlll present. Theflrstpermanentt»oth. the •fi-yea r molar: also begins to erupt at this age (see C).

1'tn111nont •

l'l!rrninent CI!!Vol ndoor

loUnl ndsor

Dec:lducus llll2rlllndoor

DedduoU> anln~

Anterior vtew of mullla (e) and rNndlble (b); left latl!r~l view of maxill~ (c) and m~ndible (d).

Ptn11onont

Pwmonont

PelmoMrt

antrollnd>or

lmnllndsor

anlne

Second permanent

Second dKiducus

main

molor

4:~,_--~-- Second

permanent premolar

c

DedduaU>

DedduaU>

lottr;l hdsar

canhe

Arst dedducw molor

Frst dec:tduoLB mdar

Dedduous - latl!llllilclsar

43

2.1

Muscles of Facial Expression, Overview

Gals----=--=- - -

aponeurotica {tpiallnlal aponeuros'tl)

Lev.ltlr lab! I

superforts alaequtnasl

~-=--~r.,•-:t,.,I--Et--- ~rlabll

S1,1perfOriS lllit!quenl!l

Z)'JI(Im;Jt~M

Lev.ltlrlabll---~~~~~------~~

minor

superfor!s

DetnSSQr arciAIOI!s

- - - -.1!11

Depressor llbOimrfor!s

A MllldH ofliufalexpresslon Anteriorview. The superfici~lli!Yl!r of muKies 'i$ shown on the right half of the face. tile dHP layer on the left half. The muscles of facial eJq~res· slon represent tile superilclal muscle layer In tile face and vary greatly In their dewlopment among different lndl\ltduals. They arise either dl· reedy from tne l)eliNteum or from adjacent mU~~Ciu to which tney are connected, and they lrueft either ontD other facial muscles or directly lniD the connective tissue of the skin. The classic scheme of classifying the other somatic musdes bythelrorfglns and lnsel'tfons Is not so easily adapted bl the faci~l musdH. Bec~use the mU~~Cies of faci~l exprnsion terminate directly In tfle subcutaMOUS fat and because tfle superildal bodyfasda Is absent In the face, the surgeon must be particularly careful

44

when dissecting In this region. Becawe ofthefrcuuneousattachments, the facial muKies are able to move the facial skin (e.g., they can wrinkle the skin. an action tempor.ufly abolished by botunnum to!cln Injection) and produce a vartety of facial expressions. They also serve a pnotecttve functiOn (especially fi:lr the eyes) and are actllle during food Ingestion (closing tne mouth for sw.~llowing). All of the facial muscles are innervated by branches of tfle facial nmoe, while the muscles of mastlc3tlon (seep. 48) are supplied by motor flbefs from the ttlgemlnal nerve (the masseter muscle has been leftln place bl representthese muKles}. A ttl oro ugh understanding of muscular anatomy in ttlis region is facilitated by dMdlng the musdes Into different groups (see p.47).

B Muscles offld'll expression Left lateral vi-. The superiicial muscles of the ear and neck are particu· larly well dbplayed from this pmpectlve. Atough tmdlnous sheet. the galea 01poneurotlca, rtretches <M!f the calvaria and Is loosely iltt3ched to the pel1osteum. The muscles of the calval1a that al1se fi'om !he galea aponeurotica are known colll!ctM!Iy as the "epicranial musde.• The two bellies of the ocdpltofi'ont;rlls (fi'ontal and octlplt;rl) can be clearly Identified. The temporop;~11ealls, whose posterior p;~rt Is called the iiU·

rlcularts superior muscle, artses from the lateral p;1rt of the galea apo· neurotica.

45

Hftnl- 2. Mu.:luoftMHnd

Muscles of Facial Expression, Actions

2.2

l..ftltDrllbil ..porlods ••equtnMI

!L.--'---

1

l..emilr llbllsl4*ioris oiHquenul

NIISIII5

Orbltulorb oarll,

il

Antlrtor

b

loatnalaat

orbital part

A Muscles of~l expreMJon: p•lprebnrl fissure •nd rue

Anle!1orvlew. The most functionally lmpoortantmusde lstheorfllai/Grlsocufl, whkh doses the palpebr~lftssure (protective reflex against furelgn matter). If the action of the orbicularis OOJIIIs lost because of facial nerw paralysis (see also D), the lou ofthls protective reflex will be accompanied by drying of the eye from prolonged exposure to the air. The function of the orbicularis ocullls tated by i1Sklng the patient to squ- the eyelids tightly shut.

b The orbicularis oculi has been dissected from the left orbit to the medial Cilnthus of the eye and reflectl!d anle!1orly to demonstrate Its lacrimal part (called the Horner muscle). This part of the orblwlarls oculi arises mainly from the posterior IKrimal crest. and Its ;action Is a subject of debate (expand or empty the laa1mal sac).

ZygamollaJS

~omlllo.ls

mlnar

minor

l..ftltDrlabll suponorls ~

I.J!oRb>r _

__,_

_ __1 ....-

anp.~llorls

.,.ulloris

llua1nllllr

IUiorlus

• B Mlllda oft.dll upnsslon: mouth • Anter1or view, b left lat•~l view, c left lmral view of the deeper laterallayer. The orllkularls orfs fonms thl! muSOJiar foundll:lon of thl! lips, and Its contraction closes the oral a perrure. Its fu netion can be tested by askIng the patient to whistle. hdal nerve par;llysls mil)' lelld tu drinking difficulties because thl! liquid 'Mil trldde back out of thl! undosed mouth during ~!lowing. The~ lits ilt a deeper lev.!l and forms the foundation of111e dteek. Dvrlng miiStlcatlon, this muscle movesfood In ~n the dental ardles from the oral Vtstlbule.

46

Orbltultrts OCIIII. l..nn.l part

.. L.evmr labll l~Orls

IJMtor angularls Bualnllllr

l.YlJamlllo.ls minor

Head -

D Muscles afhdal expression: fundf01YI111raups The various mimetic muscles are easier to learn when they are studied by regions. It Is useful dlnlc:ally to dlstlngubh between the musdes of theforeheid and JNipebralftssure andtherestofthe mimetic muscles• The muxles of the fo~ead 1nd p;~l pebral fossure are inntnrllted by the superior branch of the fulal nerve. while all the other mimetic muscles are supplied by other fadal nerw branches. As a result, patients with artral fadil nerw paralysb a~n still dose their eyes whde patients with perlphe1111l t.ldil nerve p.aralysls unnot (see p. 79 tor further deUlls).

•

• .._,) c

2. Musduo(tM Head

d

calvaria

fpicranill mulde. mnslltlngaf:

MuKit rJI the alvaria

- Ocdpltofronblls (fronta I and ocdpltal

Wrinkles the foreheiid

bellla) -

• P';llpebr;~l

g

h

--

fissure

TemporGptl~etills

()ri)lcularfs oculi, mnsisting of: - Orbital p;1rt - Palpebral pi rt - Llcrfmol port CorrugWir superdln Dopras«superdlO

Nose

Praa!na

Has no mimetic function

Tightly amtracts the skin ~tround the ~

P•lpebr11l rella. Acts on the lia1mil YC Wrinkles the ~b..-(11) ~the.,._

Wl1nkt.s the raot of the

nose ,._the naris (c) a.v.. the upper hp ond niSIIa(4)

l)lgomotlcUJ minor t

Risorius Ll!v_. llbn supertoril

LlYWII'11nguR o~s

C Olmges af hcllll aprealon 1

b c d • f

g h 1

J II

Contraction of the orbicullris oruli at the latend a~nthul of the eye expresses concem. Contraction of the con-ugator su perdlll DWJrs In response to bright su nllg ht "thoughtful brow.• Contraction of the naSIIIs constricts the naris and produces a cheery or lustful facial eJ!Prt!S$IOn. Forceful contraction of the lewtor labll superlorls alieque nasi on both sides Is a sign of disapproval. Contraction ofthe orbicularis oris eJCpresses detenn ination. Contrictlon ofthe bucclnll:or signals Sitlsfictlon. The zygomaticus majclf contracts during smiling. Contrictlon ofthe risorius reflects purposefu Iutlon. Contraction ofthe levitxlr anguli oris sigNIs se1f-11tlsfactlon. Contraction of the deprt!S$0r anguli oris sign;~ Is sadness. Contrictlon of the depnssor labll lnfmorfs depresses the lower lip

Dop11!1S0r ~tnguh oris Deprassor llblllnftrtorts

ClaMs the mouth (e) Musclt rJI the chftk (lmporUntclumg.ang and drtnldng) (I) IMge mulde af the JWC>mltlc arch (I) Small mulde of the

zygomlllc arch MuKit rAIIughter (h) El-lils the upper lip Pulls the CDmerof the mouth upward (I) Pulls the mmer of the mouth dCM'I1Mrd Q) Pulls the 1_. np downw~rd (II)

Mentalis

Pulls the skin of the chin Upwllrd ~)

Aurlcullril onlaior Auricularis superior Aur1cui;lr1J poste~or

Nedc

md expresses ptneverenoe.

Ant.rfor mulde of the •ur1de Suplrior muscle rJI the •urlde Posterior muKit of1M aurtde CUUneous muscle of the

neck

I Contraction ofthe maltalls eJq>reses Indecision.

•Ldtas refw to su!Hntr~ts In c.

47

2.3

Muscles of Mastication. Overview and Superficial Muscles

Oltemew of tile muscles d mestlmton

The m~uth is opened primarily by the suprahyoid m~ades and the fWc:e

The muscles of mastlc.rtlon In ttle strict sense consist of four muscles: ttle miSsell!f, temporalls, medial pterygoid, and lateral pterygoid. The primary function of all tbesemusdes is mclose ttle mouth and move ttle upperweth <~galnstthe lower teeth In <1 grinding action during milS· tlc.rtlon. The laterill pterygoid muscle ilsslsts In opening the mouth. The two pterygoid muscles are .-.!so ilctlve during mastlc.rtlon (for the rndl· vidual muscle actions, see A-c).

of gravity. The masseter and medial pterygoid form a muscular sling In which ttle mandible Is suspended (seep. 50).

Note: all muscles of mastlc.rtlon are Innervated by the mandibular nerve (ttllrd division of ttle trigeminal nerve), while ttle muscles of fac\;11 expression ilre lnnervilted by !he facial nerve.

• Supertldal part: zygomillllc arch (antlel'lor~thlrds) • Deep part: qgomatic arch (posterior third) ~rtton: • Masseteric tubenlslty an the mandibular angle • EMias the mandible • Protrudes the mandible ~nerwtlon: Masseteric nerw. a branch of the mandibular dMslon of the trigeminal nerw (CN V,)

Inferior temporal hne of the temporal fossa Apex and mecreal sumce of the COfOnoid process of the mandible • EMias the mandible, chiefly with Its wr1fal flben. • Retracts the protruded mandible With Its horizontal

~nerwtlon:

posterior fibers • Unilateral contracaan: masUcillllan (~MWs the mandibular head on the balance side bwanl) Deep temparalnerws, branches of the mandibular dMslan of the trigeminal nerve (CN VJ)

(i) Med..l ptefftCIIcl

Pterygoid fossa and latl!ral plallt of the pterwold process Medial surface of the mandibular angle (pterygoid tublniSity) Adlans: Bewtm the mandible ~nerwtlon: Medial pter,gold nerve, a branch ofttle mandibular diVIsion of the trigeminal nerve (CN v,)

Ortgtn:

~rtton:

I SchelllltltdthetemponiiiJmuscle

® ....... pterygoid OIIJln: • Superior part: lnhtemporal crest (gi'NII!r Wing of the sphenoid bone) • Inferior part: outersurfaaofthe lateral plate of the l*rygoldprocas

-.rtton: Actl-

~nerwaon:

C Schema\fc of tile medlill ;md lml'ill pb!ll'Siold muscles

48

• Superior part arUa~lar disk ofthe lltmporomandlbu· lar]Oint • Inferior part: condylar process of the mandible • Bilateral contraction: initiltes mouth opening by protruding the mandible and mGII!ng the ar11cul.ar disk forw.rrcl • Unilateral contracaan: eleolates the mandible to the opposlllt side during mastlatlan Lateral pterygoid nerw. a branch of the mandibular division of the trigeminal nerw (CN V,)

Pllrfeulbone

lhlntll bene

Te!1'C'O llli Is

Massetl!r.

l..1tl!r;ol ligament

superficial part

D Temponllland mu.seter U!ft lall!ral Yiew.11 Superficial layer, b deep layer. The masseter and zygomatic .arch have been partially remOIII!!d.Thefullextzmtoftheporulls Is shown In b. It Is the most powerful muscle of m.astlcatlon and does .approximately half the work of mastication. The a:msists of a superfldal part and <1 deep part. The t2mpor;llls ;md masseter act powerfully In r.arsrng the mandible and closing the mouth. Asmall por· tfon of the lateAI pterygoid Is vlsl· blelnb.

b

49

Hftld- 2.

2.4

Mu.:luoftMHead

Muscles of Mastication: Deep Muscles

Lllml

l*ll!IOicl. sLCJ('rlorpart

A l.Btel'lll and medl1l pb!rygold n!Kies Left l~ral viiMl'. a The coronoid process of the mandible has been removed here along with the l~r partofthetllmporalls sa that both pterwold muscles nn be Jftll (see p.49 Db). b Here the ttmporalls has been mmpletllly remowd, and the Inferior part of the l~ral p~d has been windowtd. The lotMJI pterygoid Initiates mouth opening, which Is then mntlnued by the supra-

see that ftbers from the lmral pt«ygold blend with the articular disk. The lateral pb!rygCiid fu nctlons iiS the guide mUKie of the temporomandibular joint. Beause Its vartous p;1rts (superior .;md Inferior) are acthle during all movements, its actions are more complex than those ofthe other mUKies of m;~stlatlon. The mrdlol pterygoid runs almost perpendicular tD the lmr.;ll pterygoid and contributes to the formation of a muscular sling that partially encompasses the mandible (see B).

hyoid muscles. With the tiiTiporomandlbulu Joint opened, 'WI! Ciln

He.ad tA mondblt,

artlo.lllr surfaoe

B MatlcatDry II'IUKU!ir 1llng Oblique posllertor view. This drawing tlurly shiMS h- the m;~sseter ind maJial pterygoid form 1 muscular sling In which the mandible Is suspended. By com bfnfng the actions of both muKies Into ll functianal unit, this sling enables ~ esful clQSure ofthe jam.

50

......,~~"-+---

Lllmlparrgold.

Wuforpart

HHd- 2. MusdesoftheHettd

Dur.ammr T~mponl

lobe

OpticEthmoid tdls ~d

!!nus

Temparab l.lrtml pterygoid, Ju~rlor put

Maueter, ~pp;ut

N~h~ryn~e

Lm!'al ~rotldgland

OnlP!wl')'nX

pterygoid,

lnftr'larpart Meehl pterygoid

Tongue ~ndblt

c

Muscles of mastSaUort, mranal sectron at the lewl ofthe tphenold tl'nus Postl!riorview. The topcgr~phyof the muscll!$ of m~stic.ation and neighboring structutl!s is ~rtirularfyWI!II displayed in this section.

51

Muscles of the Head, Origins and Insertions

2.5

M-..rc lllllldes

Jll!mad.............

~l•rw,CNVI)

andlnlpllllual-

_,..,.,m XIJ

Ocdp~IIS,

oedpltal bely Conugmrs~ll

Orlllcullrisocull, Olbltalpart LAiatmel part .-rlabll sup8forts alaeque nasi ~cusMiljor ~lalsmlnor ~.a~~t~Drang...lorts

NasaliS, IIW'IMIW,.rt

Allr,.rt Dep.-rseplln~~~l

Orbla.ollrtsorts Bucdnator Mellt
Olbkdarts orts, mandlb~l
'------- Tempnls

angutats Platysma

Medial ptlrygcld

•

(see~anclc)

A Mullde orfgfnnnd IMet'Uons on tfu~ tlnlll Leftli!ter.!lvlew. b viewofthelnnersurf.lce of tile right hemlmandlble, c Inferior view of the botSe of the skull. The origins and inM!rtions of the muscles are lrldlcated by color shading (orfgln: red, fnsu<11

Medal pttrygold

tlon: blue).

b

52

HHd- 2. MusdesoftheHettd

M..... f!I . . . . .OII ~rdhllllonof

tlfllmhi--.CNVsJ MDsmr Medial ptllrygold

Lateral l)ll!r)'gold

T1!111J0Illfs

.

.....,..., ..._._ ...... , .,... ... -CNIX.end

u..... --.p.,p. ...... _CIIIJIII) H)II0910JSUI

(not shO'M!) Gallosilossus (not shO'M!) St.ytoglos.sur.

,...._CNJQ Tensorvdl paln!nl ..-vdlp.wllt!nl Sty!OpNryngt!US

Co nslrll:to r phlryngiS medUI (mshownl

St)1ohrold Dfg&'ltlfc, anM!orbdy

l*lduiiNIId..

........ _..._, llllltlllcbNir

,......... elf

Splenlur. a pills ~ulmuu:apiU''

Obllquur. c:aplt1uuperlor RK!usapllls po.sWrior m;;jor RJ!d1ls a pills

~I

mllldes(laml iii!IVblnetW •mlllldc.vtal

,.._,

llectllsapltls latltralls ltlnguscapltlr. llectllsapltls anttr'lor

..,,iiidoldai;wluld llldn.-.•c-

_,_CNlll)

Sb!mocleldomaosttlld

pomt1er minor

Semlspnalls a pill's

Tn~pe;dus

53

Hettd - - 3. Blood Vtosselso{tlte HeDd Gnd Nedc

3.1

Arteries of the Head, Overview and External Carotid Artery

AngUiilt --~---':\ ~l'tlery

,#~-""""-~~~~~--~ <~uricUar~

tnrenorlilblill --~.._-.,-~ ..ury facial~

~~d---~~~~

artery

A CMI'WWw of the 111a'tes of the held l.clt la!l!l"al view. The common CArotid irtl!fy diYicle:s Into Ute Internal CArotid .ilrtl!fy .ilnd external carctld .ilrtery at !he CArotid blfurCAUon, which is at tile approximate level of tile fourth cervial vertehr.a. The CArotid body (not shown) Is loCAted at the carotid bifurcation. It con· talns chemoreceptors tftat respond to <*Y!Jen deficiency In the blood

54

(hypQ-Qa) and to changes In pH (both are lmport.lnt In the regulat!or1 of breilhlr~g). While !he external CArotid a!Ury dMdes Into dghtbrinches (see D), Ute rntennal arotld artery does not br.ilnch further before entering tile skull (seep. 246, cen!br.al vessels). where it mainly supplies blood to the brain. It abo gives off brinches that supply 01reas of the facial slceleton (seep. 60).

Suporfldol --_,__;:.....:.----:::...-:::....,...\ 1JI!mpcnl.aty ~-~d....---Pastrr1or

aurlcUar arll!ry

1-- - - - - - Oalplta.aty .,..."""'!"l~----- r.dal.aty Su~or -----~~_.~

thyroid irRI}'

Common

----'or:......,

caralld •rt.y

8 Bnndt• vi the exlamll canrtlcl art.ry • Left lateral view, b anterior view. The four groups of branches vi the extenlil carotid irtl!ry are shown in diffi!rent colors (1ntl!rior brancha; red. rnedilll bnonch; blue, pomrior branches; green, term InaI branches; brown). Ceruln branches of tfte ext2m1l urotid 1rtl!ry (faclllartl!ry, red) cornmunkate Wltft brandies ofthe InternII uroad artl!ry (tzrmlnal br1nches of the ophth;olmic artery, purple) through anntomos~U in the facial region II. Extncerebral branches of the lntJennal arvtld artery are de-

•

safbed on p.60. lid:!mol

an>lld .a.,

lramal aratldartory

·. u::::::=r SU~ar

thyroid arlJI!ry

•

D Onnf-ofthe bnncha of the aum.. cai'IICid 1rtl!ry (more distill brandies are desatbed In the units below).

SUbsequent units deal wttft the arteries of the head iS they are grouped in the table below, faiiDWed by the branches of the internal cai'Dtid artery and the velru. Nlme.tthellra.._

c llranct. . afthe aum.r carotid artl!ry: typlallanamrnr and Vllrfanb (after Uppert and Pllbtt)

a In typk;il caHt (50 :1:) the f1clll 111Ery, llngUili rtery, and superior thyroid artEry i rise from the rxtanilll a road o~rtEry above tfte arotld blfui'CiiUon.

11-f v.rllllts: ll,c The suJ*ior thyroid a r1:lry arises at the level of tfte carotid bifuratfon (20 ~or from the common arotld artery(101). d-f T- or tit ree branches combine to form a com man 1runk: llnguobclal lru nk (18 X), thyroltngllil trunk (2 ~. or thyrollnguofidil trunk(l ~-

AniBtlll' bnnct.s: • Superior thyroid artary • Ungual • rtJory

• llryrur. thyroid uta nd • Onl floor, tonuue

• Facial artery

• 5upll'ftdal fKJal region

Medlelllrendl; • Ascending pharynge~l

• P'- to the skull base

artl!ry

Paltelfor••ndla: • Ocdpltalartary

• Oa:lput

• Posterior aur1culor artery

• Ear • MIISt'Qtory muscles, postBvmedlal

• 5uperftdilllmlporaI

part of tht faclll sktletDn, meninges • Tempor.tl ~n. !Mrt afthuar

artl!ry

55

Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k

External Carotid Artery: Anterior, Medial, and Posterior Branches

3.2

SupmrocNe.ar - - -it ~rtety·

~-1!-.-+--~1

branches

11-T- - Superfklil

tl!mpor.JI
Superior-......&.,..;.......;;;;;;:-....,~

llbllllriJ!ry

Ru:fal artery

• Bnlnd!escfthe

• A flcTIII artery, ~Ttalartl!ry, a'ld postertor aurlallar artery andtfltrrbl'lnches Left later~! view. An Important anterior branch of the external ~rotld artery Is the fac't.ll <~rtl!ry. wfllch gives off br~nches In !he neck and f~ce. The prlnclp.;~l ct!Mco/ branch rs the ascending p.;~lati'ne artery; the fl)nsi//crr bronch ~ ligated during tonsillectomy. Of the (rrcial branches. the superior and lnferlorlablal arteries combine to form an arterial clrde around the mouth. The tem!too/ brunch of !he fildill artery. the ar~gular artery, ar~astomoses with the do~l r~asal artery. The latter vessel rs the b!rminal branch of the ophthalmic arb!ry, wflich arises frvm the intern<~! ~rotld artery. Be~use there are extensive arterial aNstxJmoses, fadal lnjur1es have a tendency to bleed profusely but also tend to htill quickly and well CIWI'ng to the copious blood supply. The pulse of the facial arb!ry is p;alpable at the anb!rioc- border of the masseter muscle inM!I'tlon on the mandibular ramus. The prlnclp.;~l br~nc:hes of the post;11rtor aurlalllr artl!ry lndude the postl!rtor tymp.;~nlc artery and the p.;~rotld artery(b).

56

ophlhalmlcartsy

Allrfculr branch

Pastl!t!or aurfculllr amry

Postl!rfor tymp;nlca!Ury

P.lrotldbl'llnch _ _ _..,...,..

Extl!mll - --+unlddutay

'-fll

Het~d - -

l. IJioodVesselsof~HetldandN«
Donal llngl.lillbnonch!s Ung.~~lartsy

;;r:TW-= - - Supr...,.,lcl lnndl

I.'

Emnwl

r>--- - o\JI:endlng plwryngiOIIIIU!y

1

12ra!dar11try

Superior

t¥oldansy 0 U'lgial1rtery 1nd lb llnnches Left lmral view. The lingual artery is the second anterior branch af the emrnal e<~rolfd artery. It has a relatively large e<~llber, providing the tongue with Its rich blood supply. It also gives offbr.~nche.s IDifle plexus arid tnnslls. I! Bnndtes flllfle l!llhrMI arattd iilrtery and their 4llsblllut1Dn: III!Rrfar, medial, 1nd pcllhrtar lnndtes with thl!lr prtndpel

di.UIInncha

...........

AntBior ll!nnchlc

• Superior thyroid arllly (see B) - Glandular branches - Superior laryn9"l • rilly -S~e~~b~nch

B Superfar tlryrald 1rtery, 11cmdlng pharyngule!Ury

lnd their lnncha Left literal view. The superior thyroid artery Is typically the first br.~nch lxlarfse from lfle external carotid iilrtery. One of the antafor brinches, It wpplles ltle larynx and thyroid glind. The asundlng pharyngul a!Ury aprings from lfle m~iil sidevlthe ~I carotid il'tey, usually arising aba¥e ltle level of the superior lflyrold artery. The level at wnl.d t a \USe~ branches from the external caroad artery does not neassa rt1y correlate with ltle murae or thewssef.

• ungual arllly(-D) -Dorsal lingual branches - SubtongualarUry

• Thyroid gland • Larynx

• stemodeldomiJSIDid muscle • Bast of tongue. epiglottis • Sublingual gland, tongue, oral floor, o~ I C3Vlty

- Ol!ep llngualart.ry • FoJCiolartery (see A) - Asandlng palatine artery

- Tordar branch - Submenu~ att.ry - Labial arterlts

- Angular arilly

•Tongue • Pharyngealw.ll, soft pallll!, ph.aryngatympanlcIll be • P.lllatine tllnSil (l1llin branch) • Or.JI floor, subma ndlbubr gland , Ups

• Nasalroot

Medllll ....ndl:

• Ascending pharyngeal artery (see a) - Pharyngeal branches - Inferior tympank artery - Pasllerlar menlngul artery

C Ort§ln flllfle -ding pharyngeal.-tery:

typlul c.e

end nrf.ntl (after Uppert and Pabst) • In typlol cases (701) the asca'ldlng pharynge.;~l ilrtery arises from the external carotid artery. 11! - d V.ltlnb: The asandrng pharyngeal artery arises from II the occipita I artery (20 I), c the internal c;,rotid <1rtery (8 'l. or d the facial artery (21).

l"'lltlllforllrandlll: • Ocdplta Iartery (see A) - Occlpbl br• nches - Damndlng bnnch • Poarlar auricut.- bro ndl (sftA)

• Pharyngetl wall • Mucosa of mkldle Rr

• Dura, post2rfor ~~ nlalfmu

• Scalp. ocxlpbl region • PDsiB'Iar ned: musdes

- stytomuiDid 1rtery

• Fidal nerw In the facial canal

- ~ll!rlor tym~nlc arllly - Auricular branch - Occlpbl branch - Paratkl branch

• 1)m panic a./lty

• PI:JSilerior side of auricle • Ocdput • Parotid gland

Hettd - - 3. Blood Vtosselso{tlte HeDd Gnd Nedc

3.3

External Carotid Artery: Tenninal Branches

Pomrtor supefar ah'ealarartl!ly

Pbell!lald branch Mlddlt menngullrtl!ly DeC~) atlfaJiamtJe.y

Antleliar tympanic artery

b

Maldh.y.artJ!Iy ~artl!ly

Bucalartl!.y

A MlllllliiiY irtary and Its branchas left later.rl view. The maxillary arll!ry Is the larger of tile 1:\W terminal branches of the eXU!rnal carotid artery. IU origin lies deep 11:1

the mandibular ramus (lmport;mt larldmark for loc.ttfng the ~sel}. The maxillary arll!ry

consists of thlft parts: o

•

Myloh1cfd

Mandibular part (bl~~e)

• Pterygoid part (green} o Pterygopalatine part (yell-)

branch

B The two tl!nnl111l bnu~he• of1M o.tenwl c.trotfd 1rterywttfl tfltlrprtndpll brancltes Brandl

o

Inferior alwolarartBy

o

Mlclclle meningeal ai1Jery (see C) Deep auriCular artery AnWrfor tympaniC artery

o o

Masseteric ai1Jery Deep tempontl branches Pterygoid branches Bucal artery

o

o

Masseter muscle Temporalis muscle Pterygoid muscles Bucal mucosa

Posllef1or superior a~olar
o o

Maxillary mola11. maxillary sinus, glng!vl Maxillary alftoll

o

ltanswrse t.ldlll aner,

o

o

Fronbl and parlet
o o

o o

o

o o o o

o

o

5I

Mandlble,lftth. gingiva (the mental branch Is Its terminal lnnch) o calvarfa, dura. anterior and middle cranial fossae o Temporomandibular Joint. external audltoly anal o TympaniC cavity o

o

o

o

Hard palate Soft palate, palatine tonsil, pharyngeal wall

o

Lateral wall of the nasal cavity, conchae

0

o Nolsal septum

Soft tissues below the zwomatlc arch Scalp of the fore"'"d and 11\!rtex Lateral orbital wall

Het~d - -

r.

l. IJioodVesselsof~HetldandN«
Anlltrtcr supertcr

Dental brandies

•hlealar atfl!ry

Poster1crsopbl branchos

" C S.lact.d clinically lmpolt.lnt bi'IIKIIH crf tt. mulllary <1rlay • Right middle meningeal artery, II left lnhorbltll artery, c right splwlopalatlne artery with Its branches that supply the n.ual cavity. The mldcle menlng1111ll artl!ry paSRS through the fortmen JpinlllSum Into the middle cranial fosR. Despite Its name, It supplies blood not Just tDthe menlngu but al.sotDthe owriylng cal\lalfa. RJJpture of the middle meningeal. artery by head trauma results In an epidural. hernatom.ll (1ft p. 262). The lnfr-tlblartl!ry is a bl"ilnch of the milllillary artery and thus of the external carvtld artery, while the suprilorblulartery (i branch of the ophthalmic artery) Is " terminal branch of the lntl!mil caroUd artery. These vessels provtde a path for a potential a nasmmosls behwen the extema Iand Inti!rna Icarotid arteries. When sewre naJO· ph1rynge;~l bleeding occurs from branches of the sph•opalat.,e artery (a branch of the maxillary irtery}, It may be necesRry tD ligate the maxillary artery In the p~opai.Jt!ne fosR (see pp. 100, 11 o; 1ft

c

also c. p. 61 ).

D Supetflclal bl!mporel wtery Left lateral view. Particularly In elderfy or ca· r:necuc: patients, the oftEn tortuous course of the fTont.J I branch of this vessel can easily be traced across the temple. The wperiiaal

temporal ilrtery """Y be lnwlwd In an In· flilmrnatDry aullolmmune disease (temporal arterltls), which can be confirmed by biopsy of the wssel. The patients, usually elderfy males, com plain of severe headiKhes.

lrgcmatlc:o- - - - - - ''-'

crbll.'llarmy

of----'--..~-

Supert'dol

llompcnl1tfl!ry

59

Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k

3.4

Internal Carotid Artery: Branches to Extracerebral Structures

CAmel!I part

• A SubdtwtslDns of tfle lntl!m;~l arotSd

Ophth~lml(

Anterlor

artl!ty and brandies thlrtsupp~

<Jrll!ry

chorolclilartery

extncerebral strucu.m of tfle heM!

~or

ammunlc&fng artery

a Medial view of the right Internal e<~rotld arll!ry In Its passage thro~~gh the bones of 1he skull. b Anamrnlcal segments of the l'ntl!mal e<~rotid artery ~nd their br~nches. The intemal e<~rotld artefy Is distributed chiefly to the brain but also supplies extr.iiC4!rebr.ill !'e9lons of 1he head. It consists d four parts (listed from bottom to top): •

S~or

l1ypophysQI artery

Cervie<~l p;~rt

• PettoiiS part

• cavernous part • Cerl!llr.al part The petrcus part of the Internal carotid artery (traversing the carotid e<~nal) and the caYI!m· ous part (tr.werslng the cavernous sinus) have a role In supplying extracerebral structures of the he<~d. They gl~ off illddltlon<~l sm.illl branches that supply local structures and are usually named for the are;as they supply. Only spedallsts may be elq)ed:ed to have a detilled knowledge of these branches. Of spedal lm· port.'! nO! is tile ophthalmic artery, which arises from the cerl!llr.al part of the Internal carotid artery (sed).

60

C<M!mo~A

31nusbl1!nch

b

HeDd - - 3. Blood Vessels ofrite HHd and N«
Longpo:!ltlrfar dllll'yamry Pl>m!rlat - - - - - - - ; ethmoldal.artl!l'y

=---------:''<---- - c~ntr.Jimml .artJ!I'y

Ophth1lmk - - - - . . . ,
•---......:,~-- Mkldlem«~ln!jeil 1118y

8 Ophthllmlcartl!ry

r - --rr'-- - - SUpraomltal Mtl!ry

""",__ _ _ _ SUpmcochiNr

.Ury

~~~~

:T-- -

MkldleJ)I~1111

-ry

b

a Superior view of the right orbit. b Antl!ri~:~r view of the facial branches of the right ophthalmic ar1l!ry. P.anel a shows the or!glr1 of the ophthalmic artery ;at the internal c;arotid artery. The ophthalmic artery supplies blood to the eyeball I~ elf and to the orblt.11 structures. Some of Its terminal br.mches are dlstrlbutl!d to the eyelid and portions of the forebe.
~ar

elt!maklalartl!ly

Anb!riar ethmoldlllrllery

Ophthalmlc:;ll'llery

C Y.15all;ir SIJpply of tfu~ nnal septun left lilterill VIew. The nan! S4!ptum Is another region in which the internal carotid artery (an-

--.....,..._.. . ,,. ! _...or-:=....:...:,_,..:'"=-'~--

Sphenopal;rtfne ar11!ry

~.---....£-;1.----

•

Maxlllaryartsy

---lnllemalc;rctfd ar11!ry

terior ind posterior ethmoidal arteries, green) meets Ute exterN~I Cilrotld artery(sphenopalatfne artery, yellow). A rfchly vasculartzed area ontheanteriorpartofthenanlseptum.called Klessdbidl's arei (blue).ls the mort common site of nosebleed. Since KJe.sselbich's area Is all area of anast.1mDSis, it may be necess.1ry to ligate the sphenopalatine/maxillary artery irldfor Ute ethmoidal ar1l!rles through an orblt.1l.i1pproach, depending on Ute source of the blee
B-- -111-- - Extl!malcaratld ar11!ry

61

Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k

3.5

Veins of the Head and Neck: Superficial Veins

~~--------1~

fugullrveln 1/IT~o:::-"""-'-------- Ext!ern~l

Jugtl~r~~eln

~------~~rw•

).!gular win

..,......'-"'-""""7;>"'\.;;;'---- i i r- - - - - Suplli!Jai)Uiilr

win

A Sup~dll he.ad and nedcwtnund tfll!lr drainage to the bndJloa:ph1lkveln l.cltla!l!l"alvfew. Theprlnclp.;~lvelnofthe necklsthelntemc!ljuguklrwln. whkh drains blood frcm the rntertor of the skull (Including the br.illn). En dosed ir1 the caratid she
62

uklr lil!in drains blood &om tne occiput (occipital vein) and nuchal ~

glon to the subclavian Yetn. ~tie tne arttwtorjugufarmn dr.rlns the supertlclal anterior ned: region. Besides these superficial Yelns. there are more deeply situated venous plexuses (orbit, pterygoid plexus, middle cranial fossa) that are desaibed in the next unit. N~ The superficial veins are most closely rElated to the deep veins In the area oftfle angular vein, with an associated rfsk of spreading Infectious organisms lntncranlally (seep. 65).

HeDd - - 3. Blood Vessels ofrite HHd and N«
~L---:----

~-------

Retnlrnandlbulllr w'n

lnb!nwl jugulllrwln

E-- - - - - : - - - Emmal Jugular win

Leftbradlk>- ---~

-=----- Suprascapular

Jill""-. .

Win

aphallc win

8 Owmew of the prfndpill veins In the had ;md neck 1St later.al VIew. Only tile more lmport.lnt veins .ilre l.abeled In the diagram. As at many other sites in the body, the course and caliber of the veins In the he<~d .ilnd nedc are wrlable to a amln degree. except

C Dr.lhJgeofbloodfromthe heid ;~nd neck Blood from the hNd .ilnd neck: Is drained chiefly by three Jugul.ilrvelns:

the internal, exll!mal and anterior jugularveim. These veins h
for the largest venous trunk. The vdns Interconnect to form extensive .iln.ilstomoses, some of wfllch extend to the deepvefns (see A. pterygoid plexus).

Vl!lln

llllgkln lhlned

lll!lallonlhl(tiD deep

anllalfalclle •lm.tnal jugular win

• lnts1aroftllukull (Including the br.-.ln}

• Within the carotid

• ectl!mal jugular win

• Head (supriciaQ

• Within thuuperlldal cenlialfasda

• Anterior

• Neck. poruons of the head

• Within thesuperlldal cerVIcal fascia

jugular win

sheath

pertldal cervlul f.lsda.

63

Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k

3.6

Veins of the Head and Neck: Deep Veins

Superior _ _ ophthamic-.eln

Angularw!n

.l::)l~--

- ----.s-- --ioll

DMp---~~~--=--~~

facial win

, ..,__ _ _ RietnxTJIIndblllf 'Win

a-.....,,_.._______ Emrnal pala!lne'Win ~~---1~1

Jugllu...eln

A Deep veins of tfle helld: p11ef'ftold ple~Q~S left laterallltew. The ptefygold plexus Is a venous network situated be· hind the mandibular ramus between the musdes of mastication. It has exten.s111e confii!Ctlolu 'With the ~djacent veins.

I DMpwlnsoftflehe.Jd: orfllt and middle cnnl;~l fossa left lateral llfew. There are two relattllely large venous ttunks In the orbit. the superior and Inferior ophthalmic vein. They do not run p.arallel to the arteries. The veins of the orbit drain predominantly into the cavemous sinus. Orbital blood can also drain externally vla the angularvdn and facial vein. 8eca~~Se the veins are Y.illlleless, extracranlal bactena may ml· grabe to the Cavl!rnous sinus .ilnd cause thrDm· bosls In that venous channel (see E and p. 93).

64

c-mous

sinus

::c=::..;;r-- - Inferior

ophthalmic win

HeDd - - 3. Blood Vessels ofrite HHd and N«
------;,--,-------7lf - - SUperior

agltt:alslru

-----.;: ,. . - --+-- CGnftuenceof ltlesl'luses

0~~~--~--~----------.

~-4--

enlsslrywil Venous plelaa

TranswM

31nus

a~Wndltle

fa ramen

C Vetnsoftflucdput

ITIISI<~Jm

Concttlr

'f--'i-;$~-

enb:si ry vein

Venous PlflWsof ----"''"----+--~"" the hypoglossal

e---~--- lntl!mal

l!eMCll'lll

Ex!Jemal wm!ml

)lgularlll!!ln

--~-~1--4~~

" -- - - - Ocdplt.ll win

Postenor 111ew. The superficial wtns of the occiput communic.rtl:! with the dural sinuse$ by w;ry of tile diploic 1/dns. These vessels, called emlss.1ry wins, provide a po!l!ntlal route for the spread of Infectious organisms lnt:D the dural slnus;a.

YenO!aplecw

s~

cphlNimlc Yl!ln Ophth~lmlu~

- - --/1-5=_..._

Angular a~ ---___;H Angtl~rwl'l

----u.

i>b!l')'gOid --"""":'':""""'i"\o~"'7"=--'l-'!l,iJ....-.'"""·•

plexus

~ltlrylll!!lns --------'"7-~----

•

lntlemal

Jugtlmoe'l'l

..,;~--------- Rdromand·

bulirYI!In

E Venousanntan101!14!n5 partll5 oflnfed'lan • Very lmport;mt cllnlc;llly because tfle deep spread of bacterial Infection from !he fadal

region may result In avernous sinus thl\lln· basi$ (infection lel'ding w clot fanmatian thatmil)'ocdudetileslnus). Bacterial throm· basts Is less common at other sites.

~nlaiVII!IIn

D alnTCII~Importllnt11MC11IIIrm.tl'on· ships Tn the f'adll region The facial artery and Its brandn~s and the terminal bra riCh of the ophthalmic artery. the dorsal nasal altery, are clinically lmpoltlnt ftSseis in the facial region because they may bleed profusely In patients who sust.lln ml~ facial fractures. The wins In this region are clinlcallytmport.lntbecausetheoymayallowlnfectious organisms to enter the cranial cavity. Bacterldrom furundes (bolls) on tfle upper lip or nose may gain access to !he cavernous sinus byway of the angularl/eln (see E).

Conneclllng Vll!lln

Velalsll-

o

Angulan.Wn

• Superior ophthalmic vein

• Cawmous sinus •

o

Veins of palatfne toMII

o

o

Supertldal temporal win

• Parietal emissary win

• Superior sagittal sinus

o

Oaipital win

• Occipital emissary win

• Transverte sinus.

o

Ocdpltal win, posterior auricular vein

o

o

Extemal vertebral wnous plexus

• Candylaremlsury win

Pterygoid plexus, tnferfor ophlhalmlc vein

o

c.wmouulnus •

mnfluena! of ltle sinuses

Mastoid emissary win

o

SigmOid sinus

• SigmOid slnta

65

Head - - 4. Crankll Nerves

4.1

Overview of the Cranial Nerves

A Functional components of the Cl'ilnlal nerves

The twelve pairs of cranial nerves are designated by Roman numerals according to the order of their emergence from the brainstem (see topographical organization in C). Note: The first two cranial nerves, the olfactory nerve (CN I) and optic nerve (CN II), are not peripheral nerves in the true sense but rather extensions of the brain, i.e., they are CNS pathways that are covered by meninges and contain cell types occurring exclusively in the CNS (oligodendrocytes and microglial cells). Like the spinal nerves, the cranial nerves may contain both affenmt and e~rent axons. These axons belong either to the somatic nervous system, which enables the organism to interact with its environment (somatic [ibf!fi), or to the autonomic nervous system, which regulates the activity of the internal organs (visceral fibers). The combinations of these different genera/ fiber types in spinal nerves result in four possible compositions that are found chiclly in spinal nerves but also occur in cranial nerves (see functional organization in C):

C Topographical and functional organlz.atlon of the cl'ilnlal nerves l1mdloall fiber

T011011111phkill origin

Name

Telenaphalon

• Olfactory nerve (CN I)

• Spe
Diencephalon

• Optic nerve (CN II)

• Special somatic afferent

t.lesenaphalon

• Oculomotor nerve

• Somotic efferent • Visceral efment (porosympathetic)

type

(CNIII)"

Pons

• Trodlleor nerve (CN IV)'

• Somatic efferent

• Trigeminal nerve (CNV)

• Special vlscoraloffen!nt (first brondlial an:h)

• Somatic afferent Cienenl-llffeftnb (101Mtk sen..Uon):

- E.g., fibers convey impulses from the skin and stnab!!d musde

spindles

• Abducent nervo (CNVI)'

• Somotic efferent

• Facial nerve (CN VII)

• Special visceral efferent (second bronchkrlorch) • Special vlsaral afferent

CieMr.OI vbanla""ralb (viKZral..,nsatlon):

- E.g., fibers convey impulses from the viscera and blood vessels

• Vlsceli11efferent

(porasympathetlc) • Somatic afferent

CieMr.OI vbanl efferalb (viKZromalur function):

- Fiben innervate the smooth muscle of the visc~a. intraocular muscles, heart, salivary glands, etc. GeMr.OI SOIIIillfc effeftnb (oo....to..-funcdon):

- Fibers innervate striated muscles Additionally, cranial nerves may contain special fiber types that are associated with particular structures In the head:

Medulla oblongata

•

VestlbuiOCDCh~or

ne""'(CNVIII) • Glossopharyngeal ne""'(CNIX)

afferent

• Special vlscoraloffen!nt (!lrird bronchial arrh)

• Spe
5p«<;;l somatic afrarents:

- E.g., fibers conduct Impulses from the retina and from the aiKitory

and vestibular apparatus Speml viKZralalferents: -E.g., fibers conduct Impulses from the taste buds of the tongue

• Special somatic

• Vllgus nerve (CN X)

• Special viscoraloffen!nt (fourth bronchial an:h)

• Special vlsaral afferent • VIsceral efferent (porasympathetlc) • Visceral afferent • Somatic afferent

and from the olfactory mucosa Spedal visaral.._:

- E.g., fibers Innervate striated muscles derived from the branchial arches (bronchiogenic e(ferrnts and branchiogellic muscles) • Accessory nerve

(CNXI)"

• Special vlscoraloffen!nt (fiflll bronchial an:h)

• Somatic efferent • Hypoglossal nerw

B Color coding used In subsequent units to Indicate different

• Somotic efferent

(CNXII)"

llbertypes

D

General somatic off..rent.

D

Special somatic

D

General vl~al off..rent.

D

Special visceral

D

General vi~al

D

General somotlc

66

~nts

~nts

•

of~Erents

of~Erents

Special visceral l!fferent:s

• Note: Cranial nerves with somatic efferent fibers Innervating the striated muscles also have somatic afferent fibers that conduct proprioceptive Impulses from the muscle spindles and other structures (for clarity, not listed above). A characteristic feature of the cranial nerves Is that their sensory and motor fibers enter and exit the brainstem at the same sites. This differs from the spinal nerves, In which the sensory fibers enter the spinal cord through the dorsal roots while the motor fibers leave the spinal cord through the ventral roots.

HeGd - - 4. Ctvniaf Nerws

..

~~~

)/ I o~rynlfW

I

Opllcn..,.

Ill Oallornolar

67

Head - - 4. Crankll Nerves

4.2

Cranial Nerves: Brainstem Nuclei and Peripheral Ganglia

A OVerview of the nuclei of aanlal nerves Ill-XII

just as different fiber types can be distinguished in the cranial nerves (C, p. 66), the nuclei of origin and nuclei of termination of the cranial nerves can also be classified according to different sensory and motor types and modalities. According to this scheme, the nuclei that belong to the parasympathetic nervous system are classified as generolvisceral efferent nuclei, while the nuclei of the branchial arch nerves are classified as special visceral efferent nuclei. The visceral afferent nuclei are considered either general (lower part of the solitary nuclei) or special (upper part, gustatory fibers). The somatic afferent nuclei can be differentiated in a similar way: the principal sensory nucleus of the trigeminal nerve is classified as general somatic afferent, while the nucleus of the vestibulocochlear nerve is special somatic afferent

Somatic sensation

Alar plate

VIsceral sensation VIsceromotor function Somatomotorfunction

• Floor of the fourth vent~de

Somatic afferent

----r'r-----...

nuclear column

(rbomboldfossa)

VIsceral afferent nuclear column

Mator nudll: (give rtse to~ [motor] fibers, left in C) Somatic efferetlt (som1tlc - r ) nuclei (red): • Nucleusofoculomotornerve(CN lll:oyemusdos) • Nucleus oftrochlearnerve (CN IV: eye musclos) • Nucleus of atxlucont nerve (CN VI: eye muscles) • Nucleus of accossory nerve (CN XI, spinal root: shoulder muscles) • Nucleus of hypoglossal nerve (CN XII: lingual muscles)

Somaticefferent nudear column

----''="*"'

~#--

Medial

b

Visceral efferent nuclear column

Latleral

Vlscerll efferetlt (vlscer~l motor) nlldel (blue): Nuc~ rmocia!H with t~ pam>ympcrthotic flffWUS symm ((jght blue):

• VIsceral oculomotor (Edlnger·Westphal) nucleus (CN Ill: papillary sp~r and cWiary muscle) • Superlorsallvatory nucleus (CN VII, facial nerve: submandlbulor and subllnguol glands) • Inferior salivatory nucleus (CN IX. glossopharyngeill nerve: parotid gland) • Dorsill vagal nucleus (CN X: viscera)

Nuclei oftht branchial rzrd> nerws (dolt blue): • Trigemlnill motor nucleus (CN V: muscles of m•stlutlon) • Facial nucleus (CN VII: facial muscles) • Nucleus ambigiiUS (CN IX, glossopharyngeal nerve; CNX, vagus nerve; CNXI, accessory nerve [cranial root]: pharyngeal and laryngeal muscles)

Nudeus amblguus

(visceral efferent,/ branchlogenlc efferent)

Olive

B Am~ng•m•nt of bn~lnstem nuciHr columns during l!mbflUfllc Somatic lfhreoot (som1tlc oensory)111d --.uloa>dol- nlldel (yell-): Stnso
ofthe Ynlibulocochkar ntrYe (CN VIII): • Vestibular part (sense of balance): -Medial vestibular nucleus - L~lvestlbular nucleus -Superior vestibular nucleus -lnfet1or vestibular nucleus • Cochlearpart(hearlng): -Anterior cochlear nucleus - Postefiorcochlear nucleus

Nuc~

Vlscerll ""--': (vl10111l ....-y) nud.r (g....,n):

• Nucleus ofthesolltarytract (nuclear complex): -Superior part (special vlsceralafferents [taste] from CN VII [facial I, CN IX [glossopharyngeal], and CN X [vagus] nerves) -Inferior part (general visceral ilfferents from CN IX [glossopharyngeal] and CN X Ivagus] nerves)

68

developml!nt (after Herrick) Cross-sections through the spinal cord and brainstem, superior view. The functional organization of the brain stem Is determined by the location of the cranial nerve nuclei, which can be explained In terms of the embryonic migration of neuron populations. a Initial form as seen in the spinal cord: The motor (efferent) neurons are ventral, and the sensory (afferent) neurons are dorsal (• dorsoventral arrangement). b early embryonic stage of brainstem development: the neurons of the alar plate (sensory nuclei) migrate laterally while the neurons of the basal plate (motor nuclei) migrate medially. This gives rise to a general mediolateral arrangement of the nuclear columns. The arrows indicate the directions of cell migration. c adult brainstem: features a medial-to-lateral arrangement of four longitudinal nuclear columns (one somatic efferent, one visceral Pffer· mt, one visceral afferent, and one somatic a(frrf!nt). In each of these columns, nuclei that have the same function are arranged one above the other in a craniocaudal direction (see C). The nuclei in the somatic afferent and visceral affrrent columns are differentiated into general and special afferent nuclei. Similarly, the visceral efferent nuclear column is differentiated into general (parasympathetic) and special (branchiogenic) efferent nuclei. This general/special subdivision is not present in the somatic ~rent nuclear column.

HHtl - - 4. C'nJnJGI Nt!lws

Vlsanl OOJiomotor

nudeus

D D

• D D D

~~~~----S~Mn~~ oftr!gemhal n~

!-7.-7------1\kldeuscf !ICIIItllrytract

• Nucleus of ocularnotarn~

VIsa!nil oculcmotarn~us

Somalk efferent nuclei General visceral eiWwnt nuclei

Special vtsceraleffwent nuclei SoiNiic lffefent nudel General visceral ~nt nudel

Special viscnl afferent nuclei

D Ganglll<~nodlted wtth cnnlll111rws Ganglia fill Inti) two main ull!gortes: sensory .and aLI1llnomlc (parasympathetic). The seMOry gangla are analogous to the spiBal ganglia in the dorsal roots of the spinal cord. They corttiln the perfkaryi of Ute ps!!l.tdoonlpo/ar nerve cells (• prlm.ilry affermt neuron). Their peripheral proce.ss comes from a receptllf, and their cartral process termlnat1!s In the CNS. Synaptic relays do not occur In the sensory ganglia. The autDI*I'IIt §IIIQIIII In the head are entirely parasympathetic. They contain the peribrya of the multipolar nerve cdls (• second efferent. or postsynoilptlc. neuron). Unllki! the sensory ganglia, these ganglia synapse with parasymp;rthetic fibers from the brainstem (-first efferent. orpregqng/loolc. neuron). Specifically they synapse with Ute periiGirya of the second tfi'el'ellt{orpcstsyntlpll'c) neuron, 'Who.s.e fibers .ilrt' distributzd to the target organ.

..

cndlll

,_

feiiiCIIJ

....1..

Oculomotor

Allllan-lc

• OhiiiY 91191on

nerw(CNIII)

ntgemiM

......

• lltgiiNNII

neNe(CNV)

ll'ngllon

l'lldalnene {CNVII)

• c.enlcUa ganglion

·~ palatln~ 91191on • Subman· db...., ganglkln

Vesllbu'dllearnene {Oil VIII) b

a-

pharyngeal

c

loc.ltSonofcnnllllnerws 111-XIIIntfle bnlnlltem ;a Posterior ~ew (with arebellum removed). b Mlds.1gltbl section, left laterill view. El(t;ept for aanlal nerves 1and II, 'Wfllch are extznsions of the brain rather than true nerves, all palrl of aanlal nerves are aJSoclilted with com!spondlng nuclei In Ute brilnstem. The diagrams show the nerve patilways le
ID .mel from tftese

nudel. The arr.ilngernent of the cranial netW! nuclei is easier to understand wltm we dmlfy tflmn Into funct!oBal nudear columns (see B). The effrtmt (motor) tN.Idel vmere the effmttt tlbers .ilrtse are shown on the left side in •· The of(mm (stnllll)') nudei wheretlte~rmtflbers end are shown on the rfghtslde.

nerw(CNDQ

• Splnll

ganglion • Vesllbulr !l'nullon

• SUp!Jior ganglion • lnfellor (pelroMI)

ganglion

~­

(OUQ

• Supaior

auaullr) ganglion • lnfellor

• I'I1Mrtl!bral and

Intramural ganglia

(nodOJe)

ganglion

69

Hettd - - 4. CIVInhJI N«ws

4.3

Cranial Nerves: Olfactory (CN I) and Optic {CN II)

t~--~~~~~~~~-----0~~~

tract ·~~:::;.........,..~----- P~rtfonn a~a·

Sernilunar gyrus Am~M~--~~~~~._--~

gyrus

A Olt.u:tory bulb ~nd olt.u:torytnlcton the biNisurfiiC& ofthe frontal lobes ofthe brain The unmyelinated axtuu of the primary bipolar sensory neurons in the olfactory mUCO$a ~re collected Into ~pproxlmately 20 flber bundln (see B). which ire referred to collectively as the ol(rnwy ni!M'. These axon bcmdles PiSS from the nasal c.1111tythrough !he a1brtform plate of the ethmoid bone into the anterior cranial fossa (see B), and synapse in the o1fodtKy lxlfb. The o1(llcttKy lxtlb ind ~S50datl!d o1fodtKy 1n1tt are not pi!rts of a perfpherill nerve but Instead constitute iln extension of the tl!lencephalon thit conulns CNS-speclftc cell types (ollgodendrocytes and micn:.glia). The olf.actory bulb and tract share with the telencephalon~ menlnge<~l covering that Is remcwed here. Axgfu from second-order afferent neurons In the olfactory bulb PiSS through the olfactory tract and medial or lateral olfactory stria, ending In the cerebr;al cortex of' the prepiriform area, in the amygdala, or in neighboring are<~s. By this short route. olf;act:ory Information Is thus tr.lnsml1:t2d Into the CNS and can be rel;ayed directly to the cerebr;al cortex.

I Extent of theolt.rdory muGII5il (olfactory regiDrt) PDrtion of the left natal septum and later.al wall of the rfght nasal c.Mty, viewed from the left slde. The olfilctory flbers on the septum and superfor cnncha define the extent of the olfactory region (2-4cm2). The thir1, unl'!lyl!!li· natl!d olfactory fibers enter the skull through the a1br1form plate of the ethmoid bone (see p. 27} ilnd PiSS to the olfactory bulb (see illso pp. 116, 204, and 372).

70

The primary sensory neurons of the olfactory mucosa have seYeral unusual properties thit should be noted. These neurons have a limited lifespi!n of up to several months, but are continLJOUS!y replenished fn:Nn ~ pool of precursor cells In the olf~ctory mucosa thit undergo periodic mitosis. New olt.rctory receptors ire thus generited throughout adult life, ;and their axons enter the olt.rctory bulb to fonn new synapses with existing CNS neurans. The regenerative capacity of the olf.actory mucosa grad~lly diminishes -Mth ~dvanclng ~ge. '-ever, mulling In ~ net loss of receptors and a slow decline lr1 overall sensory function. Notl!: injulfes to the cl1brltonn plate may damage the menlnge;al cove!'· ing of the olt.rctory fibers, resulting in olfactory disturb.'!nces and cerebrosplml fluid l~kage from the nose (•runny nose• after head triluma). There Is iln associated rfsk of ascending bilcterlal Infection causing meningitis. • The shaded structure5~redeeptotheb~l surf.lceofthebraln.

Rontalsinus ~~~---7~----~~~

flbe's

~~-01br!fonn

pw

s~

co nella

HHtl - - 4. C'nJnJGI Nt!lws

0~~------~~~~~~~~~~

cN'asm

O~lt ----..;:-;=--~~----:i ~rt

uan1--~~~~~~~

genial me bo6f

O~lt

---......:,;_+-4

radatlcn

c Eye. opCfc nerve. op1kcfll..1n. Mel optk tract

VIew of the b;n:eofthebriln, b ~roli!teralvlewofthe leftsldeof ttle brilnstem. The termln..tton of the optic tr.rct In ttle liltl!ril genlculatebodyluhown. The optic nei'Yt' is n~t a true nei'Yt' but an extension ~f the brain, in ttli$ case of the diencephalon. AnalogouJiy to ttle olfictory bulb ind tract (see A), ttle optic: nerve Is she.11fled by meninges (removed here) ind contains CIIS·spedllc eel~ (see A). The optic nei'Yt' conurns tile ax.ons of retin..l ganglion all,, Thae- tenninatl! mainly in the lateral ge· nlculate body ofttle diencephalon ind In the mesencephalon (superior collfculus. pp. 234-235).

;a

~ Because ttle optic nerve ban exteru1on of the brain. the dlnlclan can directly Inspect a portion ofthe bralnwllfl an ophthalm05cope. This examination Is lmportlnt In the diagnosis of manyneurologlcal diseases (ophthalmoscopy is desaibed on p. 133). The optic nave pams from the eyebill throc.~gh the optic canal Into lfle middle aanlal fossa (seeD). Miny. but not all, retinal cell ganglion axonsaouthemldllnetottlecontralater.llsldeofthebr.~ln lnlfleoptlc chiasm {a). The optic tract extl!llds from ttle optic chiasm to ttle lateral geniculate body (see al'o b).

D Courseoftheoptknervelnttleright orbit

l..ab!ral11iew. The optic ni!M! extend!> through the optfc canal from the orbit Into lfle middle cr;mlai fossa. It exits !he posterior side of the ey.!ball within the retro-orbiul fat (rem<M!d here). The other cranial ni!M!S entl!r the arbit through the superior orblul f!JSure (only CN V1 Is shown here).

71

4.4

Cranial Nerves of the Extraocular Muscles: Oculomotor (CN Ill), Trochlear {CN IV), and Abducent (CN VI)

Ctnbnll pedlndes afmHeNII!pholan

Trodllarni!M!

I

7 ........

~ ~-...,....-- oaJamalalll!nle

L--. ~ ~ rJ -~~amr

Nudetauf--

rudeus

tnxl!INr neM! Nudeusaf

PDns------

oculomotor

Cenll'alg.y ---?'--- ~

sub.mnce Rednudeta -+----1:s..a.t:.~

Nudt!us af oa.lamaiDrneiW

_ , __ _

n9~

C TepegNphJ alttle . ulamolllr nuda~~ Crcn:s1ectlon through the bralnstem at the le"RI of the oculoll'IOblr nucleus, superlor view. Noa: the vtscerill etrl!11!nt, pui1Sympathetlc nudflilr mmpla (\llscerill aa~lomatDr [Edinger-Westphal) nucleus) can be distinguished from the somiltic efferent nudeu complex (nucleus of the oculomotor nenll!). D Onnllewafthetroc:hiHrnerw(CNIV)

A lmq111a1 oflha IMIWI from lha bnlnst.m Almlior view. All three nerves that Sllpply the extnoculilr muscles emqe from the bralnstem. The nuclei tA the oculomotor neM! and bodllur neM! al1! located in the midbrain (mii!.MftCephalon), while the nucleus of the ibducent nerYe islocmd In the pons.

Tlw trochlur nerw mntalns ..,1y samaCir ljjlnntflbers.

c.u.... The troch._r 111M! emqes from tlw post2r1orsurflce of tlw brainsl811 n•r the midtone. c:ou nes anblriarly around the cerebral pedunde. and enlln the arbtt through the superior Ofblbl lluln. ~,__

NIX Of lttese lttree nerRS. the oculomotor (CN Ill) Is ltte only one thilt c:onUins somitlc elfaent 1nd visceral effel1!nt flben ilnd supplies _..II!Xtnoculir musdes (see C}.

• The trochBr ,.,..Is the onlycranlalnerwlnwhlch al the fibeR auutothe opporlle side (see A). Consequently, lesions rlthe nudeus or of trbers 111ffY dose Ill the nudevs, before they CTOSS

The aa~lomatur nerw c:antllns JCIIJICIIIc~ond..., ~ ftbers.

the midline. result In l»chlar niii"W polsy on the side opposltlt to the lesl.., (c...trlllltiorll poll)?. A lesion post the sltltwhelll! the I*W crosses the midline lelds to tochlel r nerw polsy on the Ymt slde as lhe lesl.., (lpollo...,l p1ll}?. • The trochlftr NMOislhe only cronlal nerve lhateme.,.a from the donal side of the brolnstem. • It hu the longest lntradu ral course of the three extraoculor motor nerws..

CounE The nerw n~ns anterlortyfnlm the ,_,aphal.., (midbrain - ~ llwl of tt.. brmstem; see pp.ll6. ~ll) ond enters the Dfblt through tt.. supe!lclr Oltlltlllssln

In the mlclbrillh (rneSI!KepNion).lb effeoentssupplymolllriiiNI'" votlan to one musde. the superlar abllque.

I OWrvlewofiMaa~lomatcrnern(DIIII)

Nudol . . . .-m• c • fllll9k • Somclllc~ ~from 1 roudNr r;;gmplex (OClllomcloblr

NJCIIus) rn the midbrain ($etC) supply tlw follOWing muscles: - IMIIDr palpebrae superlorts (acts on the upper l)'lllcl) - Superior, mecllal, and Inferior rectLB and lnfwrlor abllque (• ..ct:raaa~lar mLBdes, 111 act.., the .,.._IQ. • 1llsa!RIIefl"r.m*: Para. .piltho!dc preganglionic liffe...,b from the Vls09l orulomotor (Edlnger.-stph•O nucleus syllilpse with nturons In the dllary ganglion that In~ the following lntnoDOJia r muscles: - Puplllory sphincter - OllarymLBde

ElllctsofLillll lar_....., ClallomoiDr polsy. .....-1tr clepenclng on the atlnt rl the fr+lry. • [ffo!cts "'~ CIClJiandDr polsy (JanlyJis rltt..atracxubr tllld lnttaociAr musdes lind ltwtDr Pll pelne): - P!Dsls (drooping oftlwlld) - ~rd ilnd lawai gne devlltlon In the 6ctld eye - Dlplopl• (In the absence of comploc. ptmls) - Myd rl1sls (pupil dOllied due !llsphlnc!B" puplll•• paralysll) - Aclalm modiltiOn dlfllcultleJ (dlllry PI rolysls - lens cannot focus).

72

Nudeu• end

.llll....

en:The nudeus of the trochlur nerwlS locillld

SfKtloftrocHelw-t.turY: • The olffec* .,_ is higher lind is also devilled medially becalM the Inferior oblique (nap..,slble far elwalon and abduction) bealmes dcmlnant due to lcm of lhe superior oblique. • Olplopll.

E OWntTewaftheallduamtnerw(DIVI) Tlw abductnt nerw mntains only IOmGCic efjlnntfibers. Cllurwe Th• nerw foiiCJWS 1long f:IC!nJdclral pilth

btfln ~n'*lng the

orbit through the supertor orblti Itlssure. lllllciluiiiMI........_ • The the abdua!l'lt- is laaled in the pot\S (· midlewl bralnslam). lts fliers emor9ng Itthe lrRrior bonlor"' tho pons. • Its efferent fibers supply 110m.Jtamotarlnnerftll.., Ill a single muscle, tlwlilteral rectus.

nucleus"'

m.tsai.W-.1: nerw hiJirr: • The olffedled •Is d~ medially.

• Dlplopll.

HHtl - - 4. C'nJnJGI Nt!lws

Supeflor rectvs

==.----- SUperior

Oculcmotor

obUqu~

~--~~~~~--=~-UU~I tedLts

{dllllcled)

lnti!rior

Medial t«tus

5~ --~-.....+~-' oblque ~~~-~~~~~~ ~ lnti!rior-----,~~-a,

-

reclus

nochle.Y

--±---~HUI'

obUqu~

Supefor

s~

cplrt!lalmlc Win

rectus

liv.lt!iltpalpebr.aesuperlolls

SUperior redlis

l.iklfmal

Laafrnal ntM

gt.ld

fnxrtll ntM!

Lllttnl rectus

nochle.Yn~

Abduoent

Superior oblique

llt!M!

~~·--~-----­

Optlcn~

ni!I'Ye

Med~l

rectvs Oculomotor n~

lrmrlor

rectvs t..neul It

F CouniC olthe nerves ~pplyfng the ocullr muscles Lab!!"al ¥lew. Right orbit. ;a Lab!!"al ¥lew. b superior view (opened}. c .antenor ¥Jew. All three cr.anlal nerves leave the br.il!nst4!1Tl and enter the orbit through the superior orbital fissure, passing through the oommon tendlriOUS ring of the extraocular musdes. The obdUCJIIIt nenoe has the longert fXt10dcHol oour5e. Beci~R of this, abducent nerve p;~lsy may deYelop lrl association With meningitis .ilnd subar.ilchnold hemonbage. Transient palsy may even occur in cases where lumbar puncture has caused an excessive full of CSf pressure. with descent of the bralnstem exerting tractlor1 on the nerve. The oculomotor tterYe supplies p;~ra-

;a

n!dus

Abduc.nt ni!NI!

lnfi!tfor obtque

sympathetic lnr~ervatlon to Intraocular muscles (Its parasymp;~!hetlc flbers synapse In the ciliary g<~ngllon) as wdl as somatic motor lnnl!f'vatlon to most of the extraocul.ilr muscles .ilnd the levatDr p;~lpebr.ae superioris. Oculomotor nenoe p;~lsy may a!fl!!ct the parasymp;~!hetic flbers e1!.CI11!l¥ely, the somatic motor flbm exduslvely, or both at the same lime (seeS). Because the preganglionic p;~rasympathetlc flbers for the puplllle directly beneath the epln~rlum .after emerging from the br.airutenn, they are often the first structures to be aft'ectzd by p~H­ sure due to trauma, tumors, or aneurysms.

73

4.5

Cranial Nerves: Trigeminal (CN V), Nuclei and Distribution

Ophthimk dlwlslon

lll...ntll!phdcnudeus of trlgomll'lill nerw

T=~=~

f

M..tlr.ry--dlvlllon

Mlndllulir - - --...., dlvlllon lllgemnol.....w

1

'

./~

-rnucloulof

trlgomlnolnl!fW

Prind~(po~ne)--­

t~nsorynudOUid

trlgl!llllntl ni!M!

Spnalrudeus - - - of trlgemklal nerw

A Nuclellftd emergence from the pons. Anterior view. The lilrga' sens«y nude! of the trigeminal nene are d151Jfbuted along the bralnstem ;md tldl!nd downward Into the spinal mrd. The sensDf)' root (major p;art) of the trigeminal nervi!! thus farms the bulk of the fibers, while the mofDr root (minor p;~rt) b formed by fibers arising from the small motor nudeus In the pons. They supply motor lnnervolllon to the muscles of mastlatlon (see 1). The following .somcrtic~ nuclei are distinguished:

~

• Me~llc nudeus ofltlt t.rfgem1nrJin.rvr. proprloceplllle fibers

frum the muscles of ma.tic;ation. Spedal felt!J re: the neurons of this nucleus are pseudounlpolar ganglion cells that have migrated Into the brain. • PWndpol (pontiMJ JI!I1Sllf)' nudftlS of 1M 17igrminol nl!l"ll£ chiefly m~lata touch.

• Spinal nudeus a{ ltle trlgemlno/ nww: piln and tempenture sen· solllon, aiJio touch. A small, drcumscrlbed lesion of the trigeminal spinal .nsorynudeus leads to charad.eristic sensory disturbances In the fKe (see D).

II Cross-section through the pons at the level of emergence of the trlgemlna I ne~ superior view.

74

8 Onnllewaftlw trfg~mtn~lnerw (CN V)

The trigeminal nel"ft, the sensory nel"ft of the heild, mntalns mostly SGIIlm1c affw1nttlbers with ll smaller proportion of special viJcfral ~fibers. ItS thrMINijor somatic dhlsr- hM! the following slls ,., .......... from the middle aanlal fosu: • CJp/IIIIDimlr:dMrklll (CNV1j: enll!rsthe orbltttuaugh the superlDr Drilbl ftssuN. • ~dflmloti(CNV:}:cntmthe ~bHthrough

thefofanwn roeuncllm. • .........ciMoion (CN V,): passes through the flnmen cw•ID lhe lnfe!lar surbm the bne of the slcuH; only division a>nt.lnlng matDr ftben.

m

Nuclei •d dlllrloullon: • Sp«1ttliii$CIIOI effe'r!nt: Efflrent flben from !he rnoiDr ru:leu1 of lhe tJfgemlnal ntNt PISS In the mandibular dMslDn (CN vJl tiK

- Musdes of m.tk.ltlon (tempor.~lls, m~~sseter. medlllland lllllnl pt2rygold) - Or1l ftoor musdes: rnytoh)'oid and anll!rior bellymthe divastric - Middle .. r mUICic IB110r ~p;~nl - Pharyngal musclr. mnsor wll palatfnl • SomG~aj!Wnnl: The trtgemlnal ganglion contillns pseudounlpola r gingllon cds wt.e c.ntra libel'S pass 1111 the Sl!llJOfY NICIII of thetlf9l!ntiii1M1W (see A e). Their~~~~ flbtn 1r1nerta the flcial sllin• ..,. portjciM Ill the IIISOpNryngeal fi\UaiiSI, and the ....artor~ rlthe langue (somlllk sensation,- Q. • "~~~Jan! rffa'«rt paiJrwat': The viscera Ie!ment llben of Mimi! aanra Inel"ftl adhere to branches or sub-br.lnches of lhe trlganiMI nerw, bywhkhthey tr-1 tothlllrdestllllllon: - The lacrliNIII'IIM! (branch of CN V1) mnveys p;~raympilhllllc fillers from lhe facialnerw along the z,gomatic nerw (br1 nell m CNV2)111thelac:rfmalgland. - The aurlaolcamparalnerw (branch of CN V,)
•

~ offolrrM,..,_,.,~~fnlm the bclalrww (
D•

1ID•~Iy. the tngemlnal nenoels the ner;e llftne llrJt

br<~nchllllan:h.

CIIIIQII dl_.,.. llfdle.......rn.t-: Sensory dlsturba~eS lind defiCits may arise rn var1ous mndrttons: • Sensory loss due Ill triumattc nerwleslons. • Herpes - •ophthalmicus {iiWOiwmentof the territory of the fint division !lithe tngemlnal nerw,lndudlng the skin and/or the ~~p, by the var1all..--ter virus); herpes zmter df the fac:a. The afferent ftbers mthe trigeminal neNt OIIIR the fadal neNt, seep. 7t) are rrwoMtd In the ami!OII'fl*(rellex dDM!ne mthe e)'tlld; seeC.p.l&1).

HHtl - - 4. C'nJnJGI Nt!lws

OphthalmiC

----~__.

dMilon {CNV,}

b

Mandibular----"dMslan(~~

•

II

C CourM ;~nd dlltrtbu\lon ofl:he trfgemll'lll nerve • 1St lateral view. Thettlree dMslons of the trtgemiNI nerve and cllnl· ally lmport:lnt termiNI branch~!! ~re shclwn. All thrn divisions of the trigemin~l n~ $Upplytt1e skin ofttle face (b) and !he mucosa of the ni150pharynx (c). The anterior ~1hlrds of ttle tongue (d) receives sensory lnneNatfon (touch, pain and thermal sensation, but not taste} via the lingual nerve. which is a branch of the mandi· bular dMslon (CN V~. The muscles of mastication ~re supplieod by the motor root of 1he trigeminal nerve. whose axons artier the mandibular dMslor1(e).

NotJt: The efferent fibErs courJe eXA:Iuslvely In the mandibular dMslor1. A perlpheroll!fgemlnal nerwlfslon lnwMng one of Its dlvlslons-ophlflalmlc (CN V1). maxlllary (CN V1). or m~rldlbular (CN V3)-may cause

loss of $CNTI~tic ~n~tion (touch, pain, and temperature) ir1 the a~ lnneNated by the afferent nerve (see b). This contrasts with the more coocentrfc pattern, and more restricted modality, of sensory deficit prodUCI!d by a central (CNS) lesion inwhling trigeminal nuclei and pathways (see D).

D eentnl trfgemlnllletlan

Principal (pontine) sen50fY nucleus of tile trigeminal nerve

•

•

a Somawtoplc organization of the spinal nucleus of the trigemiNI nerve. b Ficlill zones In 'Which sensory dellclts (palrl <md temperature) a~ when CC!It.ilin regiom of the trig~ mlnalspiNI nucleusaredeslroyed. Thl!ll!ZIJOes follow the concentrfc Slllder lines In the f.rce. Their p.rtl:l!m Indicates the coiTI!spondlf19 portion of the trigeminal nudeU$ in which the leslor~ls lotited (miltl:hlng color shides). b

Sl!lderlints

75

Hettd - - 4. CIVInhJI N«ws

4.6

Cranial Nerves: Trigeminal (CN V), Divisions Ants!ar

ettlrncldal netW

SUpratrodlleolr ne~W ~-----

LXI!malneNe

Trlgemlllil ~ian

A Bn1nches ofthe ophtflalmlc dMikln (• ftrst dMIIIon ofthe trTgem11111 neM!, CN V1) Tn the orblbl region l.ater.ll view of the part!ally-clpmed right orbit. The first small lmmch arising from the ophtftalmlc dllllslon Is !he recurtent menlnge.;~l branch, which supplies sensory lnnewatron to the dura mater. The bulle of the ophth
Noii!:Thelaafmal nerve receives postsynaptic, par.asymp;llhetlcsecretomotorlibets from the zygamatic nerve (maxillary divisian) via a mmmu· nlarlfng btonch. These flbcn triVd to the lacrimal gland by the lacrimal nerve. 5¥mp;ltftetlc flbers accompany !he long dllary nerves that arise from lhe nasodllary ne~W, tnvelrng In these neNes to the pupil. The ciliary nerves ai5CI contain afferent fibers th
- - -·-E::- =ir--.-1-i--iiii-- - Z)'!JCINit'lc:nerve

B Bn1nchesofthe mlldlllrydMIIon ( · - d dlwtllonoftfle trTgem11111 nerve. CN Ya) Tn the mlldlllry regTon Lateral view of the partially opmed right miiXIIIary sinus with the zygo· matte arch removed. After giving off a me11lngeal branch. the maxillary dMslor1le.aves tfte middle cranial fossa through !he foramen rotundum and entl!!ts the pt2rygopalatine fossa, where it divides into the fallowIng branches:

• Zygomatic nerve • Ganglionic branches to the pterygopalatine ganglion (sensory root of the pterygopalatine ganglion} • lnfuaorbltll nerve The zygomltk nerve enb!rs the orbit through the trt(MorotflJt:/11 (lssiJI'I!. Its two temninal branches, the zygomilticofucial branch and zygomilti·

76

~~~"""71-----,~---

lnfr.JortJit.llne
""-:l~---!+.....::.--=::----

Alm!r!arsuper!or ah'eoln brlii'ICtle

cob!mpor~l branch {not shown here}, supply sensory lnnewa!Son to the skin CM:!r the zygomatic arch and temple. P;arasymp;llhetic. pomynaptlc flbers from the pterygopalatine ganglion are carried to the lacrimal nerYe by tfte communicating branch (seep. 81}. The preganglionic fl. bers arfgrnally artse frcm lhe f.adal nerve. The lnfraartlrtal nerw also passes through the inferior orbit!! fissure into tlle orbit, frcm which it artm the lnfuaorbltll canal. Its fine temnlnal branches supply tfte skin between the lower eyelid and upper ltp. Its other terminal branches form tfte Sllpl1lar denflll plexus. 'Which supplies sensory Innervation to the maxillary teeth:

• Anterior superior alveclar branches to tfte incisors • Middle superior alveolar branch to lfle premolars • Posterfor superlor alveolar branches to tfte molars

HHtl - - 4. C'nJnJGI Nt!lws

'Mge
ganglion

Mandibular dMslcn

Foramen

DHptl!mporal

cwale

ne<Wt

=~-----.,....-,:--',.....--

Patygoid

n-.s

C

BI'IIIIICMI ofthe mlndlbullr dMslon {•thin! cfi'IITslon of the trTgemln~~l nerw. CN In the m•ndlbul•r region

v,)

Right lateral view of !he partially opened mandible wllh !he zygomatic arch remcwed. The mixed ifferent-efferent ITiilndlbular dMslor~leaves !he middle cnnlalfossa through thefor.amer1 ovale .and enters the Infra· temporal fossa on theextemai<Jsl)«taflheb<JRoftheskull.tumenin· geal bra riCh reenters!he middle cranial foss.1 to supply sensorylnnerva· tlon to the dura. Its sen:sory bnlnches 01re iS follows: • Aurtculotempor.tl nerve • ur~gual nerve • lnferioc' <~lveolar nerve (<~I~ arries motor fibers. Re below) • Buccil nerve

The branches of!he oudailomnporollleM'supplylhewmporal sldn,lhe extem;tl auditory canal, and the tymp;lfllc membrane. The flngtJal tlfM! supplies sensory ftben to the anterior two-thirds of the tongue, ind gustatory fibers finam the chorda tymp;~ni (facial neM! branch) travel

with it. The offrnnt fibers of the in(rtHlr oflilt'Olar ni!M! pass through the mandibular foramen Into the mandibular canal, where they give off Inferior dent
Ma5SCUric nerve (mmetel' muscle) Deep temporal nerves (tempor.tlls muscle) Pterygoid nerves (pterygoid muscles) Nerve ofthetensortymp;~nl muscle Nerve of the tensorveli pal<~tini musde (not shown)

D arnkll1nenmcnt oftrtgcml'nll nerve functfgn £<1ch of the lhree ITiilln divisions of the trtgemlnal nerve Is tested Rp;trmly durtr~g the physical examination. This Is done by pressing on the M1lo'l! j!J(jtpojiltswith onefingertotest !he sensation there (ICI(al tendernus to pressure). The dtaractmstlc nerve eJCit points are aJ foii!MJ:

• 11lrCNV1: tht'supr.torbltalforamen orsupr.IOrbltal notth • For CN V1 : !he Infraorbital for.1men • ForCNV,: thementalforamen

T1

Hettd - - 4. CIVInhJI N«ws

4.7

Cranial Nerves: Facial (CN VII), Nuclei and Distribution

8 Overvtewofthet.ldalnerve(CNVII) The fldal nerve mainly
angle between the pons and ollw.lt passes Ulrough Ule Internal acousuc meatus Into Ule peCrous p;rrt of the temporal bone. whlft It dNicles into its branches: • Tbe vlscleral effeiWit flben pass Ulrough the sc,lomosloid (!nmel liD the bllse of the skull to fonn the lnt111parolld plexus (see C). • Tbe paraymp;~theUc. v1sar111 efferent. and V1sce1111 afferent fibers p;ass Ulrough the peO'Oiympl/lllc jlmn'tto Ule base of the skull (see A. p. 80). WhAe still In Ule peCrous bone. Ule facial nerve grws off the g - petrosal nerw. stapedial nerve. and chorda tympani.

/

Nudeur. of solitary tr.act

• J\bducert

Internal genu

nucleus

offlldlln~

Fact~I

nucleus

A NuclehndprlndJU!I br~~nchaoftheflldlllnerve ;a An!l!rior view ofthe br;rlnstem. showing the site of anergence ofthe

fadal ntn'l! from !he h:mer pons. b Cross-section through the pons at the level of the internal genu of the f.lcial nerve. Nok: e;rch of!he different fiber types (different sensory modalities) Is associated with a p;rrtfcular nudeus. From the flldll nLJCiars, the spedal!lfSa!«ll ~ axons tbat Inner· vm the muscles of facial expression first lt!Cp backward around the abdu~nt nucleus. where they form the Internal genu of the f;rclal nerve. Then they run foiWilrd and anerge at the lowe!' border of!he pons. The tuper'lar s.n111tory nucleus ccnt.illns IIISa!romOII:Ir, presynaptic porasympml!mc ne.Jroru. Tog ethel' with ~ (• gurt.alllry) fibers from the nucleus of the solitary tr.1ct (Mrpafor p;rrt), they emerge from the pons as the nerws Intermedius ;rnd then ;rre bundled with the 1IISt:l!nWo!DI' .axons frcm the facial motor nucleus to together form the fadalneM!.

Nuclei •ddllelllulloft. gong/lo: • ~ IIIICMII t/flrtnt: Efferents from Ule fadil nudeus supply the following muscles: - Musdes of facial U!ftSSion - Stylohyoid - Postmorbelly of Ule dlgastrk - Stapedius (stapedial nerve) • lliKBvJeffetent~: Paruympathetk presynar> tic flben •rising fnlm Ule superior saiMitory nudeus synapse with neurons In thep~ ganglion or sullmandlbulatpg/IM. Tbey lnnentatethe follOWing str\Jctures: - I.Jcrtmal gland - Small glands of Ule nasal mucosa and of Ule hard and soft pellte - Submandibular gland - SubllngL~<~I gland - Small sal!vlry glands on the dGr$Um of the tongue • ~ IIIICMII G#fffWif: Central fibers of pseudounlpolar ga~ gllon cells from Ule tenlculate ganglion (corresponds liD a spinal ganglion) synapse in Ule nucleus of Ule solilllry lract. The peripheral proC2SHS of these neurons fvrm Ule dlotdD t,mpani (gusbtDry fibers from the antmor two-thirds ofthe IIDngue). • Somcrl1c Cl/fftrnt llfC81)I)SI Some sensory fibers that supply the aurtde, the skin of Ule auditory canal. and Ule outer surface ofUie tympank membrane tr-1 by the fldal nerve and gftlku/orltgong/loll to Ule trigeminal sensory nuclei. Tbeir precisecourte is unro-n. ~Jy. Ule facial nerve Is Ule nen~eofthesemnd

branchial arch. ar.ctsGft.daiiiWWI~ury: A peripheral f.ac:lalnervelnjuryls chlrx-

terimd by pa111lysls «the muscles «expression on the alfedal side of the f<1ce (see D). Because the facial nerve conveys var10us fiber co~ ponents Ulat lefte Ule main ttunk of the nuve at different slw. the clinical ~n offaclill p;~ralysls rssubfediiD subtle varlilllfons marlil!cl by assoc:ilted disturbances of taste. lacrimation. salivation. ek. (sed, p.80).

78

HHtl - - 4. C'nJnJGI Nt!lws

~;..-o=-==---

Postl!rfor

aur!culolrnerwe

flldalnene

C F•dlll nerve bnlndlet (or the muKiet of expression

Norelfle different flber types. This unit focuses almost exdushlelyon the vlscfral ef(rrettt (branchlogenlc) tlbers for the muscles« facial expres· 51on. (The otilerflbertypes are clescrlbed on p. 80.) The mpedi~l nei'Yt' (to the Jt~pedi~JS muscle) branche$ from the facial nerve while sdll In the petrous part of lfle temporal bone and Is men· tloned here only because It also contains 'Yisceral efferent fibers (lt:s course Is shown on p. 80). The first branch that arises frcm the fadal nerve after Its emergence from the scylomiiStold foramen Is lfle poswrtor urkular nerve: It supplies 'lfsomll f/fm!nt flbers to the posterior auricular muscles and the postelfor belly of the ocdpltofrontalls. It also conveys Somall:l.ltnsOI}' fibers from the eldl!rnal ear, whose pseudounl· polarnei'Yt' cells ;~relocated in the geniculm! ganglion (seep. 80}. AIU!r

D Ccntnl•nd pcrfpheRII hdll piRI!pb • The facial motor nudew contains the cell bodies of IOIM!r motor neurons .,mlch lnDei'Vate Ipsilateral muscles of facial expressloD. The ~ (special 'Yisceral efferent} of these neurons neach their musde

le;nting the petrous b~ne. the bulk of the remaining viscer;~l efferent fibers of the facial nei'Yt' form the ln\l'llpilrGI:Icl plaxw In the parodd gland, from 'Which successi'Ye br.-anches (t!mporot zygomattc. bucml, .-and morgiiK/1 mondlbulllr) .ilre dlmtbuted to the muscles of faclalupresslon. These facial nerve branches muJt be protected during the removal of a benign parotid tumor In ordes to preserve muscle funcdon. Additionally. there are even smaller branches such .-as the digastric brilnch to the posterior belly ofUie dlgastlfc muscle and the stylohyoid branch to the stylohyoid musde(notshown). The lowest branch arislng!Nmthe lntr.tparotfd pluus Is the ctMalt brcrlldl. It joins with lfle transverse cer'Ylcal nerw. an anterior br;mch ofthe C3 spinal nei"Ye.

targets through thef.ildal nerve. These motor neurons are lnnerwted In tum by upper motA:Ir neurons in the primary sonnatomot:Dr cortex (pnecentnl gyrus). whose axons enter cordconuclear flber bundles to reich the fadal motor nucleus In the bralnstem. Naf1!: the facial nudeus has a "blpartrte• structure_ ItS upper part suppf>'ing the musde5 of the forehe;~d and eyes (b!mporal branches) .,mile its lower part supplies lfle muscles In lfle lower half of lfle f.lce. The upper pillt «the f.ldalllEn'e nucleus receiYes bllm!r.ll lnnew.ltlon, the lower pillt mntralaterallnlll!lv.ltiOrl ti'om cortical (upper) moblr neullli\S. b Cl!ntnl (supn111ude<~r) pllralywll (loss of the upper motor neurons, In this case on the left side) presents cllnlt<~lly with paralysis of the contraliteril musdes of facial expression In the lower half of the face. while the contr.alater.al forehead .ilnd extra-ocular musdes remain functional. lhU'I, the comer of the mouth $.15IS on the right (contralm!ral) slde,butlfle patient can stlllwrinklelfleforehNd anddoseUieeyes on both sides. Speech articulation Is Impaired. c Pl!ftphHIII (Tnfrlnuc:le.lr) p!11111Jysls {loss of lower motor neurons. In this c.ase on the right side) is c:har~cterill!d by compl~ p.aralysis of the lpsll.-ater~l musdes. The patient cannot wrinkle the forehead. the comer of the mouth sags• .-ardculatlon Is Impaired, and the eyelid cannot be fully dosed. A Bell phenomenon Is present (the eyeball turns upward and outward, exposing the sdera, when the patient attempts to dose the eyelid). and the eyelid closure reflex Is ibollshed. Depending on the site of the lesion, .-addttfonal delldts may be present such as decreased lacrlnnatloD and $.llrv.atlon or loss of taste sensation In the anterfortwothirdsofthetongue.

79

Head - - 4. CrGnltJI Nmlu

4.8

A

Cranial Nerves: Facial (CN VII), Branches

"-daln.,.bnndl.lndw~

IIane l.ab!ral view ofltle right b!mporal bone, petrous portiGI'I (peerous bone). The flldal nerw, accom panled by ltle vestlbulocochlnr nerw (CNVIII, not shown) , p~ses through the lnb!rnal acoustic meaws (not sh-n) to enter the petrous bone. Shortly th~hr It fwms the fJIRmal !lf'IU Df the f.ad.al nerve, which milrts ltle IDation of the gen lal~te ganglion. The bulk of ltle visceral efferent fibers far ltle musdes of expression pi1Ss through the petrous bone and leiM! It .atltle stytomutDid fo~men (seep. 79). The bela! nerve gives off ltlree

RodalntN!

GenlcUate

111g..,t....r

ganglon

nen~t

Htma of aNI for

brllnd>es ~en the genicul;b! ganglion and

stylomiiStold rv~men: • The p;ll'asympathetlcgi"Nt.wpRliNI~WW arises directly at the genku~te ganglion. This nerve INVes the anterior surface of the pelrDus pyramid at the hiatus of the canal for the greater petrosal nerw. It contln ues through the foramen licerum (not shown), l!l1tln the p~ByGold canal (see C), and passes to the pl2rygopalatlne gang lion. • The llbl,_.l n.,. piiSSI!$ to the mUK!e of the same name. • The dlonlll tympMI br.anches from the facial nerw. a'-t! the stylomastoid foramen. It contains gustlltory flbe·rs u well illS presynaptic paruympathetlc fibers. It runs through ltle tympaniC c.vlty lind pelrDtympanic fissure and unites with the lingual nenoe.

1'115t:l!rlor aurttulr lliiW

B Branc:Hng piltll!m Dlthe fildal n~n~~~: dlignllltlc significance In tempanl bane fnctures The principal signs and sym ptDms are different depending upon the exact Jite of the lesion In the course of the faclil nerve through the bone. Note: only the pslndpGI signs 1 nd symptllms assodalled wtth a partleuII r lesion site are descr1bed. 1he more per1ph1K111 the slt2 of the nerve Injury, the II!SS diverse the signs and symptoms become. A lesion at this lew! ~ects the facial nerve In acldiUon to the wstlbulochochl~ar nerve. As al'ftult, periph~r~l motor f~cial par~l)'$iS is

stylomaollald for.alllt'n

5

2

3

4 5

80

iiCCOITlpllnled by he.ir1ng loss (deilfness) and vestibular dysfunction (dtulness). Peripheral motor bclal p~~nlysls Is iccomp~~nled by dlstllrb.ana!s of taste sensation (chorda tympani),laaimation, ~nd saliV<Jtion. Motor p~~ralysl5 Is accomp~~nled by dlstllrbances of sallwiiDn ind taste. Hypericusls due to p~~nlysls of the stapedius muscle has little clinical im portanee. Peripheral motor p~~ralysls Is .accompanied by dlstu rbances of taste and sallviUon. Periphe~l motor (fidil) parii)'$IS Is the only manifestation of a lesion Itthis level.

HHtl - - 4. C'nJnJGI Nt!lws

Trfgemlnaii'M!I"IIe

Trigeminal

ganglon

VII axnmo.nlortfng bnuxlltothe

~) -~i:::··~

lnll!mal Cllnltfd artsyv.4th lnll!mal G rotld plexus

\

N.as.11glands

/

C~r--------------~11

petros;llnt!M!

Nucleus of t h e - -

~----------------~~~ Pllltfne

solttuytract

Qll'l!lllon

Gllr'l~ll.. bnr1d1es

SubmaAdlbuler ---~.._~"1 gland

c PlnJY~~~Pitflctk Wcm!l effm=n'blnd llf..:entl.tferents {gum tory ftbeft) ofthe hclill nl!f'ft

The presynaptic, parasympathetic. Vlscer.ill efferent neurons ue located irl the superior s.aliv.atory nudeus. Their axons entef' and leav!! the pons with the v!Ka'al efferent axons iS the nei'\IUS lnt1!nnedl115, then travel with the visceral efferent flben arising from the f.ldal motor nucleus. These pregar~gllonlc p.;~mympatltetlc .axons exit the br.illnstem In the facial nerve and branch fn:lm it irl the greater pelrDsal nerve, then mingle with postgangllon~ symp
palatine, and pharyr~g~l muc:oSi. Abers from this g<~nglton entef' the maxillary dMslor1 ;md travel wllh It to Innervate the taafmal gland. Vtsmal offrrent .axons (gustmlry fibers) for the ;mtetfor two-thirds of the tongue rur\ in the chorda tympani. The gustatDry fibers originate from pseudounlpolar sensory neurons In the gcnlcUite g~ngllon. 'totllch oorrespotlds to a spinal sensory(dorsal root) ganglion. The chorda tympani .illso conveys the pre.synaptk pormympothetlc 1/Jsmal effl!f'fllt fillers for the subm;andibular gland. sublingual gland. arid sm;all salivary glands lt1 the anterior ~thlnds of the tongue. These flben travel Mth the lingual nerve (CN V:s) and are relayed In the submandibular gar~glkm. Glandul.ilr branches .ilre then dlstr1buted to the respective glatlds.

D Nerves of the petrcMlJ bone Great:2r pelrDsal nerve

Presynaptic parasymp;rthetlc branch fnlm

i>ostsyn;lptlcsymp:athetlc branc:h fnlm ll'le lnt2mal

CN VII to the pUr'ygopalatlne gangtron (l;lcrlmal

carotid plexus; unites wtth the greater petroSil nerve to form the nerve of the pterygoid ca~~o~~l, thet1 continues to the pterygopali111ne ganglion .ilnd supproes the same llenitory as the gre~ter petrosal nerve (see C).

gland. ~I glands) ~.esse~' petrosal

Presynaptic parasympathetic branch fnlm

nerve

CN IX. to the otiC ganglion (parotid gland, buwl otndlablalglands. seep.U)

81

4. Cranial Nerves

Hftltl -

4.9

Cranial Nerves: Vestlbulocochlear (CN VIII)

Medial

Wltlbulor nud...

Superior _ ......r

A lludel oftlle..UIIulocochiNt ne,... (01 VIU) Cross~ through the uppe.r medulla oblong~tl. il

nudeuJ

Yetlllular nudeL fGur nudnr complt~~eS 11e distinguished:

• Supesforwstlbu llr nucleus (of Bechterew) • Lab!r.ll wstibular nudeus (of Deiters) • Medlil YeStlbularnudeus (of Schwalbe) • lnferforwstlbular nudeus (of Roller) Nom: The lnfl!rlor wstlbubr nucleus does not appear In a ao:ss-sec-

tiGI'I at this level (see the loation Gf the cranial nerw nuclei in the br~lnmm, p.228). Most of the amns from the vestibular ganglion terminate In these

four nuclei, but a smiller number pass directly through the Inferior cerebellar peduncle Into thlt cerebellum (see~)- The ¥eStlbular nuclei appear as eminences on the flCIOI' Gf the rhGmbgid fwsa (see Eb, p. 227). Their central ccnnectlons are shown In Ea.

• Ploscerfor
nudous

I

Antlorforcochlear nudeus

b Codllur nudel. Two nuclur cornplela!S 11e distinguished: • Anterior cochlear nucleus • Posterior cochll!ilr nucleus Both nuclei are located lateral to the ~~Htlbular nuclei (see All, p. 228). Their central connectiot\S are shown in Eb.

b

B O.rvlnl aftlle ..UIIul-lllurnerw (DI VIU) Thewstibulocochllar nerw is alpftialJOmGCic ll{ftn!nr (sensory)

""""'tNtmnslltunaiDmlully and functionally oftwo mmpol'll!nb: • The II'ISUflular roottn~nsmlts lm pulsu from the wstfbullr apparatus. • The cachl.r roottransmits lmpul,., from the auclltDry app111 rotu..

These raots a"' sunaund.cl by a cammon cannedlve~ue llhe•lh. They PiSS from the Inner ear throuQh the lnternalamustlc meatus to

the onbellopontlne angl1, -Mlert th.,-1ntertM br.illn. Nudeland dlllr1llulton, fG11f111a: • ~root: The mtlbularJJGnri/Son mnbllns blpollr ga01111on

cells -Mlase central proceu. [MIS tD the fourwstlbular nuder on the floor of the rhomboid fossa af th1 medulla oblong•b. Their perlphenl proa:sses begin at the sensory cells af the semicircular canals. sacculi. and utrlde. • CDc~!,_. lOCI: The spital fiiJflg/ton contlins bipolar g~nglion cells whose centlll p - PI" to the two mchlear nude!, which an: Iaten~ Ito the \Wt'lbula r nuclei In the mombold foss.J. Their pe~plt­ eralpi'OC2Ssubegln 1tth1 hllrcelluftheOigln afCortr. IMry thDrOugh physiaiiXImlflltion should include a n1pid assessment af b~ rww campon1nts (hurlng and lwolonce tests). A lesion af~ vestlbul~r root lelds tD dlrzlnt~t, whl~ a lesion ofthe Clldllelor root lucls tD r-tng loss (ranging to clea'ness).

82

Ce!Selk>-

ponllnnnglo

....,,..'-'ihiF--

Aalustlc

"""""""

('mllbulor Khwonnomo)

C Amullk: naroma In h anbellopGndne 11111le Amustic neuromas (more accurately, vestibular sdlwannomas) are

benign tu men of the cerebellopontlne angle 1rlslng from d-Ie Schwilnn cells of the ¥eStlbular root of 01 VIII.IU they grow, they com press and displace the odjacent structures and cause siCMty prvgre"ive hearing losnnd galt1tlxli. unge tumors an lmpalrtfle egress of CSF from the fourth ventrlde. co1uslng hydrocephalus and symptornaUc lntncranlil hypertl!nslon (wmlting, Impairment of c:onsclgusneu).

HHtl - - 4. C'nJnJGI Nt!lws

Viesabllarganglal\ wpo!l!arp.wt

D Vfltfbulnoangllon ;111d codllen ganglion (splr.llg;~nglla) The Ye.Stlbular root and cochlear RIOt still exist~ sep.arare structures In the petrous part oftheb!mpor~l bone.

flocxulusof -~==--~· arebeilum

hferfar

vestbular nudws

E Nuclet oftfu~vest!Wocodllen nerve Tn the ll111lnstem Antel'for 11tew of the medulla oblongata and pons. The Inner ear aDd Its a~nnectians with the nuclei ~reshown schematicillly.

a Vestllullr palt The vestibular ganglion mntains bipolar sensory ails whose peripheral processes pass ta the sanlclra~lar canals. s;~ccule. aDd utrlde. Their ax.ons travel as the vestfbular root to the four vestibular nuclei on the floor of the mombold foss;~ (further CDnnoectioru are shown on p. 368). The vestibular organ processe.s Information concerning orlentit!on In space. An acute lesion of the vestibular organ Is manifested clinically by dlzzlness (vertigo).

b Coc:hlear put: The spiral ganglia form a band of nerve cells that follows the course of the bony core of tile cochlea. It contains bipolar sensory ails whose peripheral processes pass to the hair ails ofthe organ of Corti. Their centril processes unite on the floor of the Internal auditory canal ta form the cochlear RIOt and are dls!Jfbuted to the 1:\W nuclei that ;me posteriOr to the vestibular nuclei. OUter connections of the nuclei are sham~ oni) 366.

83

Hftld -

4.10

4. Cranial Nerws

Cranial Nerves: Glossopharyngeal (CN IX) lnfslor

Nudo!us aftho IDIItary trxt,

gJivotoly

nudtus

~~ ~daaoftho

Nlldaa omblgws

IDibytrart.

rn&flor JNrt

~t~7~=~ Nudowoftho~ IDhtorytract

-'--""""'

Nuduoftho _ _ _ __..,..,::;.__

solt.lryllact

a-

..

phoryageal neow

A Nudll llfdle11DHOph~l niiW 1 Meduii.J oblongollbl, interior viii!W. Ill O'osHettlon through tbe

medulla oblongata It the 1m~I Clf emergenCie of the glossopharyngeal nerw. Ford.Jifty, tile nudel oftbetrlgemln.JI nerw are not shown (see I for further details on the nuclei).

B Onnl1ew of die IIDUOphlrynglll nMW (CIIIIX)

The glossophlryngul nerw contains pi«UUatrd~ visarol f#ffrfllt,.,_,ln adiltlon tllw!Jtral~tand somattc~tjlllm. 5ltel ..,......,.._The glossophlryngul n•rw •"*VVS from the medull• ablang•to •nd '--• the ~nlal avtty through tl. Jugulor

fo111111181. llb:lel and olllltllutl•, gong/fv: • Sp«jrriiiUcrnl. .(lmJndllogenk); The nude111•m blguus sends Its .1mnsIllthe canstr1ctDr muscles ufthl pl\ar,nx (• pharyng&l lnndlu,joln with thewgus tDform the plgryngeol plalll) and Ill the stylopiiMyngela ( - C).

•

~"OIJaniii~~~):Thelnfettorslllol;ltoly

nucleus sends pamympadMtic ~plic fibers totbe otic ga~ ~ ~-ffomtheotlcplgllonll'ldlstrlbutedtll

tbe ]Mr01ic1 gland and ID the bucallnd labW panels(- a and E).

c.ennr procasesd~stnSOIY

• Somcllfr. .

•

c

..

ganglion cells loated in the inf1Ticraniol~gonglion or ~ ln(rJfwgGIIflllon of the ~pharyngul ntn~e tenninate in lhe spinal nudeus oftl.trigemln•l- The perlphtnl prooesses of lhese cell• lrfR from: - the posmricrthinl ofth• tongu•, .soft palm!, phlryngul mucou, .1nd tllnslls (liferent ftbers for the Qlll relle~C). see Ill and c - the mUCOH ofthe tympanic awlly and ellltlchian tube (tympanic plexus). see II - theskln oftill! u~an~lurond audiiDryunol (blends with thl! lwTIIDry supplied by the VIIJUS ntrvt) and the Internal surface of the tymp;onlc membnuw (JNrt ofth• tymp1nlc pluus). • 5p«1(11 ~SICffVI ~ ecnt111l prootSSeS of p$81doun~lor gonglion tills from thl! Inferior gor~~~llon lllrmln•tlln U.e superior p.1rt of the nudeus of the solitary trillct. Thtlr perlph•ral processes orlglnltle In the pos12rlor third ofthe tongw (sjUIUI:Gry ltbers, see e). • \1mnll ~ Sensory flbers f'n)m the following reaptllrs termlnol21n thl! Inferior port of th• nude111 of th• sal!tory lr.Jct: - Chemoreceptllrs In lhe carotid body - P'rasul1! 11!ceplln In tl. a ratld sinus (s• f) O.O.Io,.......rly,theglos$ophlr,nge~lnerwlslhe-oflhethlrd

branchialan:h. Isolated lesloftl of the glaaophlryngul nerw 1111 ral1!. Lesions of U.ls nerw .1re usu.Uy ilccompanled by lesions ofCN X lind XI (va~us nerw .Jnd ;oausory nerw., cnmlll p.1rt) beCIIW.II thrw IWWSeml!lp jantyffom thejugularforllml!lllnd RIll~~~~ lrpyln ~sku~ fractures.

84

HHtl - - 4. C'nJnJGI Nt!lws

Ungual b111nthi'S TymJ)Oilk nerve - -

C lnn!d••oftl!.glph;lrynge;JI nerw beyDnd

Supt!rlor g;Jfl!lllon

1~--='f---

1M tlalll base

lnfe
Left late<;al view. Noll! the close relationship of the glossoph.aryngeal nerve tD the vagus nerve (CN X). The carotid sinus ls supplied by both nerves. The most lmpomnt brallChes of CN IX seen lrl the dlagrim are as follows:

!Jinglon

• Pharyngeal branches: three or four brinches for !he pl\arynge
vagus nerw.

I'Nr)\'lgul plexus

pha~lbranches

body.

• Tonsillar brallChes: for the mucosa of the pharyngeal tonsi1 aoo lts sum~~Jndlngs. • Ungual branches: somatosensory flbers ind gustitDry flbers for the posterior third of the tDngue.

Clroud sinus

Trlglm'niln~

aa:uopharyngNI nerw

/~

Mandbular

dMslon

~nlc

plexus

"'-./\, . . . . - - - - - - - - - - Lesser petrosal I'M!r"¥e

Otic

Dll'~lan

Postganglionic parasytn· pathetlcflbefs (run a short d1stance w1lll IN! JiUriCU~por~~ln~}

lnftrlar

g~ngllon

D lr;mcheufthe glllssoph;lrynge;~l nerw lr1 tfletymp;mlc catty Left ant2rolmral lltew. The tympanic nerw, which passes through the tympanic canaliruiLII into the tympanic cavity, is the first branch of the glonopharynge;~l nerw. It COfltilns vlKeral efferer~t (pmynap1k para·

symp;ltbetlc) flbers for the otic gangllor~;md somatic alferer~t fibers for the tympanic caVIty and pl\aryngotympanlc (Eustachian) I:IJbe. It Joins with sympathetic fibers from the carotid plexus (via the carotiCDtym· panic nerve) tD form the tympanic plexus. The parasymp;ltbetlc fibers tr.wd asthe lesser petrDsal nuve tD the otic ganglion (see p.99), which pi'OIIfdes parasympathetic Innervation tD the parotid gland.

E VI tee I'll cffen:nt (plruympriu:tk) flberuf the iJossopharyngeal nerw The presynaptic par<~sympa!hetlc flbers from !he Inferior sallvatory nucleus leaw the medulla oblongata with the glossopharyngeal nerve and branch off as tile tympank nerw lmmedlmly afta'emerglng from the bue of the skull. The tympanic nerve dlllldes within the tympanic cll\llty tD form the tympar11c plexus (seeA,p.144),1Mllch Is Joined by po.stsynaptic sympathetic fibers from the plexus on the middle meningeal artery (not shown). The tympanic plexus giftS rise tD tile lesser petrosal nerw. which leiYeS the petrDus bone thrDCJgh the hiatus of the canal for the lesser petrosal nerw and ent2rs the middle cranial fossa. Coursing beneath the dura, it passes through the foramen laarum ID the otic gar~gllon. Its fibers enter the aurlaJiotempor;~l nerve, pau tD the facial nerve, and Its autonomic fibers are dlstr1bull!d to the parotkl glaoo via facial nerw branches.

15

Head - - ... CnmltJI Nerw.s

4.11

Cranial Nerves: Vagus (CN X)

The vagus ntn~e CDI1talm gmeq!IIMI Jlledal V~sctr.r effeRntftbm .,well.s vtsarallllliennt and SOIMik llltlnntftbers. It his the most t:lllll!nSive clistrbD>n of.. the a.lill (vagus • "lllglbond") and CDIISists ci aanbo I, .,..,..., tt-.clc, ...:lllbdomlnal p«ts. This unit dells ""'lnly with tlw vag.. nerw In tlw hud lind n~~ek (Its thoracic •nd 11bdomln~~l ports lire de:Krf~ In the volume on the Neck ;md lntemill Org~ns).

DarMI ¥1!1111 nudeus

SIN af..-gene.: The VIllUS nei"VIt tmc
Nuder •d dlllrllulllln, gongllo:

• 5P«kJJIIISCMJ/«ffmnt~): ~tillers from the

)'gular foramen

Splnolnudeus ofb1gfmlnllnfiW Dai'Mivag;~l

N.=.u~~~tho! nuclous a~por1Drport

Nudtw of the IO~'Yli'ICt. l~orport

=~ Nudeus •mblguus b

Olivo!

A Nuclei of the wguuwrw. ~ Medulli oblongabl, anmior view showing the site of emergence of the vagus nerve. It CnJss..sectlon through the medulla oblongata at the level of the superior olive. N'* the various nudei af the vagus nerve and their functions.

The RUCkus crmbiguus contains the

JOmOPc ~t (branchiogenic) fibers for the superior and Inferior laryngeal nerves. It hasa somatotopic organlzlltlon,l.e., the neurons for the wpmor laryngeal neiVI! are above, and thase far the itt[MDr laryngeal nerve are below. The dot:sal nucleus of the vagus nnw Is located on the floor of the rhomboid fossa and mnbllns presynaptic, par.aym pll:hftlc vlsanl efferent neurons. The sonnauc ~nt fibers whose pseudounlpobr g1ngllon cells are locat2d in the superior Qugular) ganglion of the vagus nervi! urminate in the spinal RUCkus of tift! ~o/ nerve. They use the vagus neM! only as a means of cunveyutce. Tlle central processes of the pseudounlpolar g;mgllon ails from the Inferior (nodose) ganglion ilre gustatory fibers and visceral afferent ftbers. They mrmlnate In the nucleus of the sollt1Hy

Inlet.

86

nudeus amblguus supply tiM following musdes: - Pha'Yngeal muscles (phlryngul branch, Joins wtth gfosso. phlryngealnerw to fonn tiM ph1ryngul plibUS) 1nd muscles of the soft palate (lem:or wll peLitlnl, mulde af IMIIa). - Alll•ry"!!""l muscles: TIM superior I•'Y,...I nerw supplies the a10lthyrold. while the lnferfor llrynget~l nerw supplies the other laryngal muscles (the orfgln af lhe llblrs Is described on p.ll). • GI!IMI'IIIvlsarollfrttwlt~- Dg): PinaympatheUc pn!SyNiptic ~from the do~l¥11gll nudeus MrVe syNJlM in pn!'letmbral or lnlnlmural ganglia wllh pasbynapUc fibers Ill supply srmath muscles •nd glands af: - thon~dc vlsall and - abdominal vtsan as far • the 11ft calrc ftealre (cannon-Mhm point)• • Somatic l1{frnnl: Central pniODeS ci pseudaunlpobr gongllon aoh ~Dated In tiM .suporior(;>JuiDIJ ~ cithewgus tl!rmNte In the .pn. I roudeul d the trtgemlnll rww. Tlw ~~~fila's orl!lln*trom: - the 41nln the ~cnnlll ross. (menlngul branch. see Df). - • small- at the skin ofU. Dlt) and Ullmll .....,.,.,.,.. (..rra.llor br..dt,- Dq. n....ncu~ar ~Hand!

pinna<-

Is the onlyc~ branch dthewgus rwrw.

• 5P«kJJIIISCMJI.,..,_ C.nlnll p.-.s at pse.udounlpoi;lr ga ngllon cells from the lmrlor nodose g1ngllon tennlnll:e In the su perlor port of the ru:llvs of the solltlry tract. Their peripher~l processes supply tiM WtJt buds on lhe epiglottis (see Dd). • Genmol viJizrDI o/femrt: The perlkary• mtt- .tfarw1ts •re •loa located In the Inferior ganglion. Their Clelllnl p~DCZ~Sesllnnln•.. In the Inferior part at the nudeus olthe $01brytflct. Their peripheral prooesses supply the following oreas: - Mucasa at the lawer pharyl'lllat Its junction wllh the esophagus (see De) - la'Yngeal mumu •bow (superfor !.ryngul nerve) •nd beiCM (lmrlor l•ryngeal nerw) lh•IJiotdc 1perture Dll) - ~ure reaptorJ In the aorUc an:h (see De) - Chemoreoep4Jors In the parHortlc body<- De) - lhoradcand abclomrnalvtsc.ra <-Dol

<-

Dewlopo•••LIIIy, the VIgus nerw Is tlw n Jlxth bronchial •rch.

mlhe fourth and

Astructure of ~n~jor dnlal lmportllnce Is the I'I!'CUmllf laiJngeal - . whkh supplies vrsaromoUir Innervation to lhe only muscle that 1bducb the vaal canis, tiM ~rlorcrl.,..rytenalcl. Undmral destrucUon of this -leads to hoilrwness. 1nd bllilten~l destruc:JJon leads til respiratory dlsnss (~).

HeGd - - 4. Ctvniaf Nerws

- - - l'haryng""l brandies - - SUps1or

Lal")''l!!""'........e

11112malbr>ndl

!-:'---:7- - Leftlrhrior

ltlghtlnferlor -~~e--;·,;,.,­

loryngoolnorw

loryng..lnorw

01~1d ---~::;#-J;~~----

ExtJemalbrinch

muscle

Subdnlon or111ry Bntehlo- ----+-n--

b

aphollc trunk

C Br1nches of the Wlgus nerve (CN X) ~ tht neck il The vagus nerve gives off four sets of branches In the neck: philryngeal br~nches, the superior laryngea I nerve. the rewrrent Laryngeal nerve, and th~ ~cal cardiac branches. The Inferior laryngeal nerve h the b!rmlnal brinch of th~ reament laryngeal nel"4. It winds around the subcLavian artery on the right side and arvund th~ aortic ilrch on th~ left side. On that side It Is In dose rebUonshlp tD the left: main bronchus. A lesion of the Inferior laryngeel nerve (e.g., due to pressure from a nodal metastasis of bronchlill Cilrclnomil or from an aortic aneury5m) may lead to hoarseness (lntr1nslelaryngeal muscles). The Inferior larynge•l nerw passes dose to the posterolmrill aspect of the thyroid ~nd. IT'Iilldng It suscepUble tD Injury during thyroid optBtlons. For this r.Yson, ,;m otolaryngologi$l should asse:A the function of the laryngeol muscles prlor1o thyrvld surgay. b Muscle suppOed 1Pf the superior Ia ryngeal nerw.

~~---_.~~--~

cordiac brlll
•

c

e D

•

Vlsce.n l1nd -rydlltrtllutlon of the WIUSII-{CN X)

87

Hettd - - 4. CIVInhJI N«ws

4.12

Cranial Nerves: Accessory (CN XI) and Hypoglossal (CN XII)

C Onnfi!W ofthucr:lll!lliOI'JMI'Ye (CN XI)

TM accessOI'f nerw Is considered by some authors to be an lndfpfndmt p.art oftt. wgul nerw (CN X). It conblins both visceral and somlllic efferent flbe~. and has oM cranial and one spinal root. Sites el em....-: hsplnal roat emerges from the spinal cord, passes supertcwty, •nd en~ tt. skull through the (onrmen mOllllum.. where It tolns With the cranial root

from the medulla oblongata. Both roots then 1etw the skull lllgether through the jugular{otomen. While still within the jugularforamen, fibers from the cranial root Pllll to the wgul nerw (lntlernal branch). TM spinal porUon descends to the nuchal region as the l!ldlernal branch ofthe accessory-.

A Nudaus W

CIDUFM ofthl _.,1111"11'11

Posterlorvlewoftfte br.llnstem (wl!hthe ce~ bellum l'l!moved). Fclr didactic l'l!.asons, the

muKies are displayed from the right side (seeC for further details).

\

~;.~ b

B LetTon of tfle 1cauory nl!f'ft (onthe~slde) <11

Posterior ¥few. Piralysls of tile tripezlus muscle causes drooping of !he shoulder on tfte.aft'ectl!d sllie..

88

b Right inte!'Oiatefal view. Wltft p.aralysls of

tile sb!rnocleidomastoid mus~ it is difli· aJit for the patient to turn tile head to tile opposlll! side igilnsta resistance.

NudeT and dlllrllutlotl: • Ctonial tOOC: The special visceral effefent flbe~ of the accessory nerve that arise from the caudal part of the nucleus amblguus JOin tt. Vli!IUS nen.oe and are distributed with the recunent Jaryngeel neMt. They lnneMtlt all of the laryngeal muscles eca!pt the criCDthyroid. • Splnol tOOC: The spinal nudeus of the accessOfY nerw fonns a nanvw a~lumn of celllln tt. anUrlor hom of the spinal cord at the level of C2-CS/6. After emerging from the spinal cold, ItS somalfc efferent fibe~ form the -mal branch of the •a:zssOIY nerw, which supplies tt. trape21us and stemodeldornastold muscles. Elfwdsof•-ry-lnJury A undateral lesion results In the follOWing cletldts: • TAipeliuJ ~ chantcte.U.d by drooping of the should.-and difficulty raising the ann alxM the horlmntal (the t111perlus supports the ser111tus anllef1or In eleVlltlng tt.ann past 90'). The part of the accessOfY nem thillt supplies Ute traperius is wlnentble during operations In the neck (e.g., lymph node biopsies). Beause the lower portions of the muscle ~~also Innervated by segments 0 and C4/S, an InJury oftheaccessOIY neMt Will not mult In 011mplete trapezius p.aralysls• • ~IISIDid prwlysis. chantell!lbed by lllrUCDIIIs (wry neck. I.e., dl~ cultytumlng the head Ill the opposite side). Beause thll mulde Is supplied wuslwly bytt.accessOfY neMt, an InJury to that neNe causes ftacdd paraly· sis. W'lth billtentl lesions. it is difficult for tt. pellent to hold the head In an uprlght position.

HeGd - - 4. Ctvnial Nerws

E Dwnll-ofthe hypoglaulnerw (CNXII)

Hypog.....ltr1gane ~n rhomboid fana)

The t.,pogloswl-11 ' Pl"lr SOfNit1c: elftrtnt tNt supples the IIIIISCih-

Hypoglo~

MMI!

Ollft

Nud...atthe

hypoglossalnenoe

a

lheh)opo-

\

9...... .......

I

Foramen

In the floor cfdle rhom bold bsl. Its solllll:lc tft'erentftbers emerge from 111e medulla oblol'lglti,IHving the c:ranilll Col'olltythi'OIIgh tile hypoglossalcanalillnd deKitndlngl.t.1111ott.vagus- The

..

gkllsalnenoe

Cross-section through the medulli oblo!lgm at the level of 111e ollva. This section passe5 through the nucleus of the hypl)glossal nenoe. It nn be seen that the nucleus lies just beneath the mom bold foss~ and raises the floor of the fossa to furm the hypog los~l tr1gone. Because Ndl nucleus

lllooct..MIIsb_,_,......The nudtus of the hypaglaaolneJWis1aaled

magnum

Clnalof~

D NudeTofthe~loeMinenoe il

lllredtt.~.

Nudruul"

Cl splnaiMMI!

~lossal nerw enters the ~of the IDnguubcowthe 1¥1!d bDne onddlll:rlbuta Its fibers there.

i$ close to the midline, it i$ mmmon for more extensive leJions to Involve the nuclei on both sides, producing the dlnlc.al manlfatations of a bilaWr.~l nude<~r lesion. b Anterior view. The neurons contained In this nuciNr mlu mn COITI!SpOild to the alpha motur neurons of the spinal cord.

D_.lltlon: The hypoglossal nerve sup-

pfles 1lllnt~nslc 1nd ut~nslc musdes of the IDngw (acept for the po imlgiDUus, CN X). It can be mnsldeM 1 "zlorath" wntral root rillherth1n 1 true cnmlll- Thever.tral fibers of C1 and a ti'IWII with the hypl)glosul ...,.. but l - I t again .Jfter a short

dbtanoe to form the superior~ ofthe (deep) InN! QU\IIcalls.

l'nlanlr31

of..,_.._,_,.,._,ury:

sr.cb • Centr1l hypoglossal p11r111ysis (supnonuclur): lh•tangue ct.vlau WRI'f from the side of th• lesion. • Nuc:INr or perll)hlral pual~ls: The

Loft and right

;}''· r \1

gmiDglouiB mLISCies

~ dwlltaIDwlnltt.ilfKtl!d side due to 1 P4 epo~ld!nl e d nuculir ldlon on the healthy side.

c

">-- - - CGrtlmbulbor

stylogi1151U5

fiben

musde

F Dlltrtbutlon oldie ~lolull'll!rw Cenlro~land peripheral course. b Function ofthe genioglossus musde. c Deov!Mlon of the tongue !:owlrd the paralyad side. The nucleu~ of the hypoglossal nerw is innerwted (upper motor neurons) ~ cortic:;ll neurons from 111e contralateral side. With a unlllltl!ral nltdfor or pertpherol lesion of the hypoglossal nerve, die tongue devl.ib!s tDwird die side of the lesiOn when protruded because of die reliUve dominance of the healthy ga'lloglossus muscle (c). When both nudel in! Injured, the tongue cannot be prGtruded (flaccid paralysis). •

....... MMI!

.......

• 89

Hettd - - 4. CIVInhJI N«ws

4.13

Neurovascular Pathways through the Base of the Skull. Synopsis

.................. (t) Supe
® Aloduant

tflllmlc"'!h ® Lllc:rirNI .-...

® Oculornomr

® l
(!) Nl110C11111ry

"'""" nen~e

®'n'octllnenoe

.............

,_

Middle nwril'(lml artl!ty. mentn9N! br.anchofCNVl

...._....

blalldGIIYI

Trlgemlllll ne~~~e.CNV), lesM" petrosAl nen.oe

Intimal carotid arl:erf, tntl!mll c.Jrotid 1)'11'p;rthetX plelws

blalldGIIYI

nttmal carotlchrllly. Intimal carotid~ patti eac plexus

....._.,...._

Antm'ortympanic ,.,_ tuy, choRia t}mpani

Mlcldle mtrin99 arlely. mtrin99 brand! ofCNV1

..._,.._I_ Hldafla!Yifor

LesS
(I) ntl!miiJugl.farwfn

® QO$sophlr}n •. _

.................

(1)~~-

lllllllafGI.....

® Acaealory nen.oe

<» nferlor petmsal

GrtftrpdrOj\oll-

sinus

®"""""'or "*'hgNillf1lery ull'pfn!Nne llf1lery lind wb

(1)1/e:titiluloalcNNrn...., ®Facialn

£mtssuywln

® Acaw:lrynenoe ® l'lferlor

Spbal win

~ahfrus

®fo511!ricr rnenhge.lllf1lery

® Amdor Sl)(nal •rt«r

~ogloaal-wnoiiJ

pleJUof hypogloaal anal

® l'osllrfcr ® Spinal root of 19f'NI artl!ty aai!IIICI')'IMIW ® Spbal coni ® Verb!bnll

A SltK wfwre nerws ;md - " ' p;111 through the skull INA IJ!ft half of dra!Mng: fntem.-al'lltew of the base of the skull. Right half of drawing: exlli!malvlew of!he billie of the skull. Because the opening ln1D tfle crilnium is not identical to the site of emergena on tfle extemill

90

-

.............

1rtay

C.O.....GIIYI

Condylu antaarylll!ln

.-aspe<:t of tfte base of the skull for some neurw.~sa~lar structures. the site of entry Into the cr.-anulm Is shown on the left side .-and the site of erne11ence Is shown on !he right side.

Head - - 4. Crankll Nerves

Opening

'Tnnsmltted structu,..

lntemll view,INse of the skull Anterior c:ranllol foua

• CriDrifonn plate

• Olfactory fibers (collected tD fonn CN I) • Anterior and posterior ethmoidal artery

Mickle Cl'lllnial fossa

• Optic canal

• Optic nerve (CN II) • Ophthalmic artery

• Superior orbital fissure

• • • • •

• foramen rotundum

• Maxillary nerve (CN V2 )

• Foramen ova&e•

• Mandibular nerve (CN V,)

• Foramen spinos!.X11

• Middle meningeal •rtery • Meningeal branch of CN v,

• Carotid canal

• Internal carotid artery • Carotid sympathetic plexus

• Hiollls of canal for greater petrosal nerve

• Greater petrosal nerve

• Hiallls of canal for li!S5er petrosal nerve

• Li!S5er petrosal nerve • Superior tympanic army

• Internal acoustic meatus

• • • •

Facial nerve (CN VII) Vestlbulocochlear nerve (CN VIII) Labyrinthine artery Labyrinthineveins

• jugular foramen

• • • • •

Superior bulb ofintemaljugularvetn Glossopharyngeal nerve (CN IX) Vagus nerve (CN X} Accessory nerve (CN XI) Posterior meningeal artery

• Hypoglossal canal

• Hypoglossal nerve (CN XII)

• Fora men magnum

• This foramen has an oval shape because it transmits the motor roots of the trigeminal nerve (CNV) for the muscles of mastication.

• Meninges

• • • • • • Extemal•spect, baseofthe*ul (where different from internal aspect)

Oculomotor nerve (CN Ill) Trochlear nt!rve (CN IV) Ophthalmic nerve (CN V1) Abducent nerve (CN VI) Superior ophthalmic vein

B Principal sites where neurovascular structures pass through the skull bilse Note: The eltternal opening of the foramen rotundum Is located In the pterygopalatine fossa, which is located deep on the lateral surface of the base of the skull and is not visible here.

Medulla oblongata, spinal cord Vertebral arteries Anterior spinal artery Posterior spinal arll!rles Accessory nerve (CN XI): entering spinal roots Spinal vern

• Incisive canal

• Nasopalatine nerve

• Greater p;~latine foramen

• Greater p;~latine nerve • Greater p;~latine artery

• Lesser palatine foramen

• Lesser palatine nerves • Lesser palatine arteries

• Foramen lac2rum

• Deep petrosal nerve • Greater petrosal nerve

• Petrotympanic fissure

• Chorda tympani • Anterior tympanic artery

• Stylomastoid foramen

• Facial nerve • stylomastoid artery

• Condylar canal

• Condylar emissary vein

• Mastoid foramen

• Emlssaryvetn

91

5.1

Face: Nerves and Vessels

This chapter describes the topogr.ilphlcal aBatomy of the anterior .ilnd l~teral aspemoftfle he;! d. It is ii$$Umed th.irttfle reilder is<~lre<~dyf.lmili~r with the skeletal, muscular, ind neui'OYilscular anatomy lllll!tr.lted In preYious chapters. The most dlnlcally Important regions around the eyes, no.s.e,and ears aredescribed in separatechapben.ln tflischap!zrthe

various reg!orts of !he t'ac!!. head. .ilnd neck are dlspl~ on the ewnnum"-d p.ages (left-band ~de), whne the odd·num"-d p.ages (righthind side) p!'O'IIIde Information on functional groups of specific iniltDmlcal structures .ilnd their dlnlcallmportance.

~--J.f-":'~_,;lfi~f\-:~E---

SI.JIIllorllftlllnl!rfl', latml branch

·-~·~ .":'.';~~::.--- S...,..aorllftal nl!rfl',

medial branch

f.tdllni!I'W. -+':4-H~.!J.o ll!mpcx;~l

,\li+IHI -- Aur'lc:Uoll!mpcr.ll

branchH

nerve

Angulmu'lay

E UU~·~- s~alumpcnl

~ndwln

artl!ryandwin ,~,...-A~~!---k-.~1H-•LJ--

lnfractbltal artl!l'y andnerwe

Fatlalnen.ot, - - - - '""", marginal mandl· bularbranch

Fadalarto!ry - - ---f'llE and vein ~---

A SupHfldllnenresl!nd-boftflel!ntl:ftorhdlln:glon The sklflind f;m:ytlssue have be1!n removed to demofiStrate tfle superficial muscular layer, the muscles official expression. This laya'has been p.arlially temCM!d on tfle left side of the f.ace tD display underlying portions of tfle musdes of mastfeidon. The muscles of Cl!Pression receive their motor lnr~erv.rtlon from tile {odc!l netW.. which emerges laterilly fi'om tile parotid gland. The face receives Its sensory lnnerv.ltlon fi'om

92

Ment.l n~

the trigemlnalllC!rl'e. whose tfn-ee terminal branchn are shown here (see E), Brinches from !he third dMslon of the trigeminal nerve iddltlonally supply motor Innervation to the muscles of mastication. The face receives most of its blood supply fi'om the mrmo/ mmtid ar!l!l)t Only small aren around tile medial and lateral cantil! of tile eyes 01nd In the forehead are supplied by the Jnll!ma/ CGroffd or!l!ly(seeB).

HNd - - 5. TopogmphlcGI.Ano1Dmy

Dorsai~~~S;~Ial'll!ry

- - -+ - -.,;.,'-7----

"("-~--+----

Xilr...::;;;;,...,....___:~r-----

uural palpebral

Sup11101111t<JI<Jr11!ry Medial palpebral
lll'ti!I!H

./"\ -- - - Superfidlll tl!mponl1111!ry

r- - - - Dttunal

ca ralld .wtl!ly

8 DlstoriiU'Ikm of the atam;ll Glrolfd art.ery (red) and tntl!mal urottd illltll!ry

{brwm}lntfleflce Hemodyn~mically signific;~nt

anartomoses may deYelop betwHn ttle$e two ~rtaial tml· tortes. Even il ~rtred reduction of flow In Ute Internal carotid al'tl!ry by ~!herosclerosls may

not le.ild to cerebral Ischemia, as long as there Is .ildequate compensatory flow tftrough the superficial tl!mpor.ill artery. If this is the case, tftm ligation oftfte superflcial tempor~l artery Is conttalndlt."!ted (tile artery might otherwise be ligated, for example,. In a biopsy to confirm Ute diagnosis of temporal arteritis;~ p. 59).

C Triilnguludlngerzone lndlefiiC8 This 1011e Is mart.ed by !he pnesen1:2 of venous connections from Ute face to the dural venous sinuses. Bec:i!use the veins in tftis region
Superlat

ophltlalmlcveln

Ophthalmic artl!ry AnQularartl!ry - -df <~ndveln

Sltefor - --t\ • galtlg ltle angularwfn

____.- Superlat ~ petrosalslnus

r----s...,aarflltol MrYe

------ lnhrlor --petrosal slrw

(br.aru:naf~V1 )

..---;~----.,...--- Maldl;uy~h$

...,...._...:......_ Sigmoid

s'tlus

'+-- - - - lnfrlarbltal I'I8W (blllndlof~V:z)

'----'------==- - lntemlll ]ugularwln

E aJntcallytmportilnt sftes of etnel'llei'ICII!

aftflethn!e trtgeml'NII nerve brandies

D Clfnluly lrnpolt.ilnt vucular ftlltloMhlps In tfle flce Nok the connections between the extl!ricw of

the face and Ute dural slnus;es. If .il purulent Inflammation develops In Ute "danger zone• (see C), Ute .ilngularvefn c;~n be

ligated at a standard site to prewnt Ute transmtsslol'l of lnfectfo~K organisms to the c.avemoussinus.

The trigeminal nerve (OIV) is the major ~ ~tic sensory nerve of Ute heild. The dtagram shows Ute stll!s of eme!'gen1:2 oflts lhnee lil~e sensory br.ill'lChes: • br~nchofCNV1 : supraorbitlll neM! (supraorbltlll foramen) • branchofCNV2: lnfraorblt.ll nerve (tnfraorbltlll for.ilmm) • branchofCNV3: mental nerve (mentlll foramen): see alsop. n.

93

5.2

Head, Lateral View: Superficial Layer Supetftdal~r.ll

SUpetftdaltemparal artl!ry, p.llfet.11 br.anch

artl!ry, frontal br.~nch

nti'aodlltll nerve

(br.anchof trigeminal nerve)

~a:lnmr

muscle

Ment.11neMe (branch of trigeminal neMe)

Br.~nchts of parG!Id plexur.(fadal M'lle)

A SupHfldllveaekmdnervaofthehud l.clt lall!fal view. All the irteries visible In Utls dlagrilm irlse from Ute mrmol Ctl1'0tld ortl!ry, which Is too deep to be Wible In this superfldal dissection. The lateral he.'!d region is dr~ined bytheertf1f!Gijugulor!il!in.. The facial vein. however. drilns Into the deepa-lnternaljugularveln (not shDWn here). The (adal rtfiYf h;ss divided ln Ute parotid gland to form Ute p.arotfd plexus. whose br;mches leave Ute p.;~rotld glarld at ItS anterior border and are distJibuted to Ute f~tial muscle$ (see C). This la!J!r~l

94

Ext!!mal

fugularwln

head region also recdves sensory lnnuvatlon from brinches of the frl· gemlna/ nt!fVt {see D). while Ute portion of the occlput visible lt1 the drawing Is supplied by the gi'MfT and lessf!r OCCQlrtDI tl1!M!S. Unlike the trigeminal nerve. thecaipital nerves origina!J!from thespinal nervescf the cuvlc
HNd - - 5. TopogmphlcGI.Ano1Dmy

SUperfiCial tlemporal <111:2fy,l'rontal bra nell

Mlddleb!m-

pot;llal'tl!ry

Superior 101b1011<111:21'y

lrhr'lor -----. lolbiOII<111:21'y

lnfetlar /

.alwolaral'tl!ry. mental bra nell

::::z:'

Mallinal - ----,-=,..-·71

I

./

Submemala~

mandlbulilr bnlndl

-11- - - - Motorbrandles ID rtylohyald and d\Q&rlrlc {pos!l!rlor belly}

Facial <111:21y

8 Superllctal br.lndles oftfle l!ll.tl!m;ll Glrotld ilrt.l!fy 1St laterill VIew. Tills dlagr.ilm shows the .ilrterfes lfllsolatlon to demonstrate their branches .ilfld their relationships to one another (compare with A; seep. 54 for det.illls).

C FiKhiMaw(CNVJI) Left lateral lllew. The mwdes of f.ildal expression receiVe all of their motor innervation from the seventh cranial nerve (seep. 79).

Aurlalo!l!mporal nenoe

Trigeminal

gangran

-.l~!l!ll!~:;;-_,.;,_..~~-- Mandlbulilrdlwlslan !\']) ~H~iiiiii~="'--- 1..1t2!'al pterygoid musd~

~ltll --":-!~'7

netw

1nrer!or - --i-.::;....---::-.,.--

,.zo:.

alveolar Ol!n'e

Bualnator mulde Mental netw ---F:=;.~·

Mylohyoid m1.11de

D Tl'lgemlllll nerw (CN V)

Left l;ateral view. In the region shown he<1!, the he;~d derives its somatic sensory supply from three large branches of the trigeminal nerve (supriloltlltill nenoe. tnfrilorbltill nerve, and mentoll nerve). The diagram II· lwtrates thelrcnurse tn the skull ilnd their 5ltes of emergence In the .iln· tetiorf.lciall'l!gion (see the .ilnberiorviewon p. 92). The trigeminal nerve Is partly a ml1!.ed nerve because motorflbers lr.IVel with the marldlbular nerve(= third dMslon of the trigeminal r~erve) to supply the muscles of mastication.

E Nef'ft tellftorles of the Iatini head and n«k Left later.ll view. Noa: The laterill head ;and neck region receives Its sensory supply from

aanlal nerve (trtgemiNI nerve ;md Its brilnches}, ;md from the dors.al rilml {greattr ocdpltill ne!'Ve) and ventrill r.ilml (lesser occipital nerve, great aurirular nerve, transwrse cervical nerve) of spinal netVI!S. The C1 spiN I nerve has a ventral root, contllnlng mawr flbers, but r10 dors.al root: Ittherefore provides no SEnsorylnnerviltlon to the sklr1 (I.e .• It hillS no demnatome). OM

95

Head, Lateral View: Middle and Deep Layers

5.3

S\CH111rCKhlearneM,

supnartltal nerw

------:lf/#;~lt!o..­

(br.~nclld~V1 )

FlldalneM. bucal bnnc:he Menlll~ ----&~.1/l

{bnnc:hof

CNV:s}

fadall'll!rW, marghal mancf· bularbranch

A VKselnnd ncrvcufthe lntennedlllc I~ l.clt laterill view. The parotid gland hils be\!11 reiTIOYCd to demonstrate the struc:tllre of the lntrip.uotld plexus of the facial nerve.. Note c.ertain nervu hall!! been di!SCribed in pn!Yiaur. units. The ftlns have been removed for dartty.

96

lntr;parotld plexus

HNd - - 5. TopogmphlcGI.Ano1Dmy

Allrtrulot!em·

Po.stl!!for sl.pelfor aM!alar
por.aln~

Superfldilltem·

pollii..Ury IJI!Jer.al ~dmusde

lnfraorblt
Middle menlr>geal artel)'

BucalnerYe

MD!IIaly
Bucxfn.atllt

mustle LllgualneM

~riot ;~M!alarn~

Inferior Mlooedar
8 Vencfnnd m:m:ufthedecp III)'Cr l.clt later.~ I view. The masseter musde and zygomatic arch have been dMded to gain .ilccess to the deep strucllJres. Also, the r.ilmwo of the marldible has been opened to demonstrate the neunw.asrular struc· tures th.iltti';M!rse It The veins have been completely removed.

5.4

Infratemporal Fossa

Temporals musde

Superi!claltAmporal aruryand~n

DeEp temporal nerws

Superior aM!ollr-. postl!tlor sLCM!flcr alveolar branches Maxillary arury llucul<mryllld-

Medial pl21')901d musde UngualnerYe Faclalaruryand~n ~musde

Deep ttmporal

a runes Auricu~ral

ntM Latml~d

musde FaclalnerYe Ramuscfmandble lnfetforaM!olar aruryand n~ Stl!modeldo-

INI!tl:lldmusde

A

lelttnlr.lt.l!mpar.~lfom, supl!l'fldall~

Ulteral VIew. A separate unit Is devoted to the Infratemporal fossa because of the m~ny roucwres th;at it contains. The zyg~matit ~rch and !he anterior half of the mandibular ramus hive bem re!MVed In this dlssectlor1 to gain aa:ess to the Infratemporal foS;Sa. The mandlbu·

Jar canal has been opened, andUie Inferior alveolar arll!ry and nerve can be seen ent:trlng the canal {the accompanying vefn h~ been removec:l}. The m;WII~ry artery dividn into it$ tenninal branches dHP within the lnfratempor;ll fos.sa (see 8).

5~112mpcr.ll

Ternpcr.llls ITWC!e Deeptl!mporal ner.'H lnfnlorllltalarl:el'y

arury andwln utet;~l pterygoid muscle

Aurla.foll!mporal

nerve Sphl!nopa~he arury

Po:stB1or superfor


Trigeminal nerw, mandibullrctlltslon Middle menlloeal arury

Bucal aruryand n~ Maldlary arury Bucdnator rmscle UngUilln~

P.ldalartl!ryandwll Massetl!rrmsde

8 lett1'nlratil!mponl fol11, deep layer l..ater.ll view. This diln!rs frvm the previous dissection in th;at both he;td$ of the lateral pterygoid musde have been partlally removed, so that only their s!IJmps are llfslble. The branches of the maxlllary artery and mandlbcJiar dMslor1 tafl be Identified. Bytareful dissection, It Is possible

98

Me;lial pterygoid muscle Faclllln~

lrhrtor
to define Ule site where the aurfCIJiotemporlll nerve (branch of the mandibular division} splits around the middle meninge~l ~rtl!ry b~ fore entering the middle crar~lal fossa through the foramen splnosum {seep. 59).

lind -

5. Topographlml Anafumy

Mllllary dlvlllon Ophlhllmlc d!wtslan Mandlbu!.rdMslan None d IB!sor

tymponl tadai i'IOM! -----,~·

"bclal unal Tensortympani mUKit

C Left atlc pn1llon and Its roob loatH deep In tile lnrr.tlemponl-.,

Medii!I Ylew. The small, flit otic ganglion Is located medial tDthe mindlbulilr nerwjust lr.-

ferlor to the fora men oville. The puiiSym~etic: fibers for the parotid gl;lnd are relayed In the ganglion (seep. 85).

c

lnflftcr

UngLIII nt
lnflfkr

Unguol none

alveolarrwve

Milllllary dllottlon Mlndlbullr dolslan

•

Mo!nlng• l b111nch

alveolar nerw

Deep12mpo1111

""""" llur.alnerw _

Mecllillp1J!I')'ll01d

•

-~------:;;

___...;.;:! =0( --J

7

lnfttlor

Unguol none

1lveolarnerw

nerw Alrl::Uo· 12mpo11111'10M!

UngUIIro.rw

Bucdrwtar mlllde MalHII!rlftlsde D llnnches afthe mlndllulilr division rn the lnl'nltllrnporel ,_.

Left imAI view. The medlirl pterygoid muscle can be ldentlfled deep within lfle foSSil. The third divil;ion of the lligemi"'l nerw paSJeS

Medlill pllr}ogold

mlllde through the forilmen ovate from lfle middle cranial fGssa to enter the infratempo~l fossa. Traveling with It are mumr fibers (matDr root) lhilt supply the muscles « mastication (only a few of the liben are iiiU51rated here).

E YirtrlntJ ot tile left mlllllll.-y .-ll!ry

Lateral view. The course of the m;ndllary artery Is subject to consld8<1ble varliltlon. The most common variants are listed below. a Runs literal to the literal ptl!rygold musde (common). • Runs mediiIto the liter
d Runs between the branches of the inferior alveolir nerve. e Runs medial 1D the trunk of the lnfel1or ilveol.a r nerve.

99

5.5

Pterygopalatine Fossa

Pb!rygopalatlne fossa

~d~g--------------~

pataune artery l't2f)I9QmDIII;ry --__...:'-----7 flss~re

Zygom;rtlc l)n)
~------- l.e$sef

palitlne ;utery

A CourM ofthnrtarfK In the left pt81Jt0p;llatfnefosM Urteral ~ew. The lnfr.rtemporill fosSil (see previous unit. p. 98) Is continuous Mth the pterygopalalfnefosSil shown here, with no de.-.r line of dem~rcation betwl!en them. The anrtomic~l bound~rie.J af the pterygopala11ne fosSil are listed In B. The pterygopalatine fossa Is.-. aossroad for ne\lrovascular structures traveling between the middle cranial fossa, orbit. nas.al c;Mty. ilnd or.al CiiVlty (see !he pasSilgeways In E). lle
c u.,.er lr.lndles of tile m.ullary ill'teJY The maxlllary artery consists of a mandibular part. pterygoid part. .and pb!rygopalatine part. Because the vessels of the mandibular part lie ouWdetltearea aftltedlssect!on. they a~ not listed Jntltet.1ble below (seep. 58). lnnch Motldll>cdor port seep. 58 l'tf(ygoSd ptl1t: • Masseteric amry • Deep temporal arteries

• PWygoldbrand'tn • BIICCill artery

• Masseter muscle • Temporalls musde • rttrwold muscles • lluocill mucosa

~port:

D!Jedlan

lanlemg Jbuclure

• Post!rior supe~>ior al\lll!olar

Anterior

Maxillary tubenHity

amry • lnfraorbltll artery

l>cstleflor

Ptler}gold proc:JeSS Qaller.ll plate)

Medial

~endltularplate of the palatine bone

Lort.efal

- Lesser palatlnurt.ery

Communlc.1t.es with the Infratemporal fossa Ilia the pt:erygomaxillary fissure

Superior

Gremerwlngofthesphenoldbone,junctlon with the Inferior orbital fissure

Inferior

Op.ens Into the l'l!ti'Opharyngeal spa at

100

• Des«ndrng palatine artery - Gmb!r palatine artery • Sphenopalallne artery - lateral posterior nasal arteries

- Posttrlor septal brandies

• Maxillary molars. miXI11ary slnus, glnglva • Mulllary alveolae

• Hand palate • Soft palate. palatine ton~ll. pharyngeal w.all • l..at.eral w.all of nas.al cavity, d'toanae • Nawl sepCIJm

HNd - - 5. TopogmphlcGI.Ano1Dmy

lnhorbitlllllln'e

Orbit<~~ br.uldles Gingllonk br.uldles

Ma:dlaryneM ~~~orbltlll--~------~==~----~

Nasapalallne ne~W,

IMt.n!

medial .and laller.ll superior pa.stleflot nasal bt.anches

~------ Plo!rygopalall'le ganglion

==i------ Nerwof pterygllid anal

Nlaopelltfnenl!l"fl', - - - - - - - -_..,.

postl!dcrlnfwlor n&'l.llbrardles Gl'llilte-

palitlne.-

Gruta-l)etrO/I;IInerw

----:----=-""'"

D COurse of tile nerves In die left p1ief'ygo~U~'-tlne ro.. Latl!r.ll view. The m.MIIary division, tile second dtvlslon of CNV, passes from the middle cr;mlal fossa through the forilmen ro!:IJndum Into the ptt!rygop.alatiAe fossa. Oosely related to the maxillary ni!M! is the para· symp.athetk pterygopalatine !Jilngllon, In whkh preganglionic flbers synapse with g<~ngllon cells that. In tum. lnnew.rte the lacrimal glands and the small palatal and nasal glands. The pterygopalalfnegangllon re-

«ives ~ pre~ptic fiber$ fram the gre~~ter petrosal nerve. This nervt' Is the parasympathetic root af the neMIS lntemnedlus branch af the f.t. clal nerve. The sympathetic flbers af the deep pettoSill nerve (sympathetic root), lila! the Sl!ns«yfibersofthe maxillary nerve (sensory root),

piiSS through tile g<~ngllon without syn;~pslng.

E Pill!ls.Jgew.ll to the p11ef'ygop;~I;!Une l'o:!ls.J and trart!lmlttl!d neui'OIIIilscular structures

.........,.

Comes from."

F0111men ro!:IJndum

Middle cr1nlal fos:sa

• Maldllarynerve(CNV:z)

Pterygoid canal

Base ofthe skull

• Nerve of pterygoid anal (grater and deep petros.~! ntr~~eS} • Artery of pterygoid an<~l with .acccmpanylngvelns

(Inferior aspect) Cirtmr palallnecanal

hlale

• Greater palatine nerve • Descending palatine <~rtt!ry • Grater palaUne <~rtery

r-pala1:lnean<~ls

hllte

• l.aserpalatlnener\'1!5 • Laser palatine arteries (t2mllnal branc:l1es of descending pala11neartl!ry)

Sphenopalatine foramen

Nawlavrty

• Sphenopala11ne artery (and <~ecompanylng \'elns) • Medial and la1er1l wpel'lor and Inferior postel'lor nawl brilnches (from nasopala11nenerw, CNV.zl

lnfer!ororbltill flssult!

Orbit

• lnfraorbltill na'\'1! • Zygomatic nenoe • Orbltil br<~nches(from CNVz) • lnfr<~orbltill ;utery (and <~ecompanylng\'elns) • Inferior oph1halmlc Win

101

6.1

Oral Cavity, Overview

A Upu111dllbl'lll cn.es

-~-:--Angle of

An'terlorvlew. The upper arid lowerllpsme«attheangleofthemouth. The oral ftssure opens llltO the orill alllty. Changes In the lips noted 011 visual inspecticm may yield imporbnt diagncsticdues: Blue lips (cyanosis) suggest a disease of the heart.lu~~g. or both. while deep nasolabial creases may reflect chronic dlseises of the digestive trict.

moulh

8 Or~lavlty Anterior view. The dern:al arches wtth the alveolar proce!.Ses of the maxllla ;md mandible subdivide the oral cavity Into sever.ill p.irts (see also C): • Ot.ill vestibule: the p.itt of the cral cavity bounded on cne side by the tftth and orlthe other side by the lrps orchecb. • Oral c.ntty proper: the cavity of !he moulh In the strict sense (within the dental arches. bounded posteriorly by !he p.ilatoglossal itch). • Fauces: the throat (boundary with the pharynx: palatopharyngeal arch).

Hard

p.Mitl!

P.lllltogloml

SCft


p.Mitl!

P.llatopharyn-

:-.~~u..:.---I.Mlla

gealarch

1-- - P.llat'he

Faudal lslhmus

ton Ill

The fauces communicate with the ph;lrynx through the faooal isth· mus. The oral avlty Is lined with llOillceAtlnlzed, stratified squamous epithelium !hat Is moistened by seaetfons from the S.illllr.lry glands (seep. 113). Squamccacell carcloomas ofthe oral alllty .are particularly common in smo~ and heJvy drin~.

Hard

T!lnls

p.wlltl!

lllbarlus

Oral --::----~t:'I'~Lr#---- Frenuklmof Yl!:ltb&.fe lower

rp

1-Jrwry

~odway

Soft Oralclllllt:y propt!f

p.wlltl!

U>'Uia Nasof.lucl;ll lsltlmus Hyoid bone

Epglcttk

C 01'11anlziltlon ;md bourldarfes of tile Ol'ill CiiVIty MldSilgltt.ll sectfo11,left tmral view. The m~&Sdes of the oral floor .ilnd the adjacent tangue together constitube the inferior boundary of the oral c;wltyproper. The roofoftheoral avlty Is formed by the hard palate 111 Its anterior two-thirds and by the soft palate (velum) In Its posterior third (seeF). The uvula hangs &om the soft palate between the or.ill

102

plt;lryn:x

o,. phlryn:x

I.Oiryngoplt;lryn:x

cavity and phirynx. The tceraunlzed s1ratlf!ed squamous epithelium of the skin blends wtth the nonki!r.atln!Ud stratified squamous epithelium of the e~ral avity at the vermilion border e~f the lip. The or;I cavity i' located below!he nasal C3111ty and antertorto the pharynx. The mldport'kln of !he pharynx. called !he oropharynx. Is the area In ~Mllch !he alrw;ry and foodway lntenect (b).

HHd -

Postl!lfor ------.=~~~IY

"·~

_,...____.

~"•1*:0.....,*--~,.,..=.---- Nasopala1tl~

Sl!ptallnndlu

n~

· - ----~;;t:;~~~~

foramen

)'-l~+:...,;,----ll!.--- Mtd'an palaUne

sutune Cnsrtl!rp;~latlne

!laW

CI"Ntl!r p;~latl~

Le~rpallltlne

foramen LA!SUI'PIIItfne foramen

Pllerwold

-....;:o~'"?'!!ii

hl~n~~lus

~,__

lnfr.aorbltal.antl!rlct superlct .alveolar branchK, michie superior Ml,oeol~ r bra nell

_

__;,.,.~~-- NasopalaUn~

ner\'e

D Neui'GRIClll;ir structures of the hard pilite Inferior 1/iew. The arteriH and nerves af the hard p;rlm (skeletal anat»my Is shown on p. 28) pass downw;rrd through the lncls'llle foramen and the grea~rand ies,ser p.alatiAef~ ramlna Into the oral cavity. The nerves are terminal br;rndtes af the trfgemln;rl ne~Ve's m;rxlllary dMslon (o.J V1), and the arteries artse from the territory of the maxillary artery (Aeither are shown here)

E

Sensoryrnnervltlonofthep~lml ITIIICIIA, upper lip. dleetrs. and sfnghr.a

lnfenor VIew. Notr: that the region shown in the drawing

lnfr.aorbltal - -. -.....:.. nerve,pcnrlct

--~~--~~~.---c~

~aM!olar

p;~latlne

ntM

branches

Ptllllne aponeuro.s!J ---~~t=:f:::.,__..:;::;\:...._~ lllusalus ---::=---~~ LMJiae

. .~~

~~--~--~dJ

Soft--..:......-F..iF4h

().Ilite

6. OnJICDVII.y

~~M~--.;_-

TenscrwU ()M~nl

~.,....-.,----- (J,wtorvell

()Mitlnl

recdves sauory lnnerv.rtfon from different branches oftile trfgemln;rl nerve (bucul nerve from the mandibular diVIsion (CN V3, all other bran the$ from the maxillary division, CN V1).

F Musclu ofthuoft p.alltlt lnfenorlltew.Tilesoftpalatefonnstheposterlor boundary of the oral c.Mty, separating it fram the oropharyruc. The musdes are attached ;rt the midline to the palatiAe ;rponeurosls. which forms the connective Ussue foundation af the soft palatJ!. The tzn-veli palatini,levatorlll!!li palillinl. and musaJius uvulae can be ldentl6ed In this dissection. While the tensor veil palall:nl tightens the soft palate, simultaneously opening the inlet to the pharyngotymp;rnic (auditory) tube (seep. 145), tfte levator veil palatinl raises tile soft palate to a hol1mntal position. Bolh of these musdes, but not the musaJius uvul~e. also contribw! structurally to the lateral pharyngeal wall.

103

6. Orvl Cavfty

Hftnl -

6.2

Tongue: Muscles and Mucosa A SUrhu ilnlltomy of the R~t~Uill rnUCCBil

Ungllll tonsil

Fo~amen

awm Polilllne

ton•ll

DoiJLm


Body of tong..

' - - - - - ApOKof

Supericlrview. While the motor prope.rtla of the tGfi!IUt! Me func~ lly Important during mutlatlon. swallowing. and spe~klng.lts eqtlllly Important sensory functlalls InClude tJstll! and fine bctlle dlsalmlmtlon. The wngue b endowed with a very p-"ul muSCl.llilr body (seeQI). The upper surfKe (dorsum) of the wngue Is covwed II¥ il highly Sf»' cialiad mucosal coat and conslsb, fioam fioant to back. of an api!X (tip), body. 11nd root. The V-shaped funvw on the dor.ul surface (the sukus termlnalls) further divides the tongue into an ~~~rior (oral, presulaO part and 1 postErior (philryngeal. postsulal) port. The anterior port comprises the anterior two-thirds of the tongue, and the posterior part campri!ellhe postErior third. N: the tip of lfle "V" Is the foramen czc:um (veJt!ge of embryologlal migration of the thyroid gland}. This subdivision Is a ~ suIt of embryvloginl development and explains why each part has a different nerve supply (see p.107). The mucosa of the anterior part Is composed of numerous papillae (see 1), and the connectlw! tls:sue betw.:en the mucos.al surface and muKU Iatune contains many small saliwry glands. The physician should be fa mlllilr with them, iiS they may give 1tse to tumors (usually malignant). The mw buds are bordm by serous gl11nds (.see lb-e) thilt ire known also as wn Elmerg/ond$; they produce a watery secretion that keeps the tastll! buds dean.

tongue

Aliform

'llllat>t

l'lpllla NcnlleNdnlad sll'aCI1Itd } ..,.mom oplthdum }

Unguall!pO~

r-Sulaa 'MIIofpoplll l -

} Unguol mLIICios

l:m'etory ductof. SI!I'QUS91•nd

,::..:..,.=,....;;; "

~Sen!..

/

.

glands (IIDn Ellner glands)

•

•

~ Fcllm

npatpop11a~

popllae

(priolly
epfthellum) Conne
c

Serous gllnd

..

8 Thc,.pll•cvfh""'guc iii Sectlonil block dlagl'lm of the llngt~~l piplllae. b~Types of piplllae. The papillae ane dMded Into four morphologlally distinct types: b vallate papillae: enclrded II¥a wall and cantllnlng abund.;;mt bstll! buds.

104

e

c f\lngiform papillar. mushroam1"'pcd, located at the sides of the tongue (they hi~Ye mec"'nlal receptors, thermal receptors. ;md ustll!buds). d Filiform papillae: thread-shaped papiUae lf1at are seruit~ tD tactile stimuli. c FGJi;Jte papillae: located on the pos~orside$ ofthe tvngue. containIng numerous taste buds.

HftHI -

5. Oral Ccrvffy

Do111m ofiDngue

c

>------ v.rt!GIImuode ofiDngue

)""'.....,..,.~-Th11'1$lootiW

muscle ofiDI'Que

Musclesafthltangue a Left latmsl view. b anterior view ofi coronal secUon. There are two sea of lingual muscles: extrtnslc and lntrtnslc. The extrinsic muscles are ~ched to specific bony slb!s outside the!Dngue,while the inb'insic mt.11cles ~ no attachments with s!Geletal structures. The mrlmlc llngu;d musdes lnd ude the: • • • •

genioglossus, hyogloJSU5. pala!Dglossus, stylog IQISSUS.

The inb'insiC lingual muscles include the: • • • •

suptorior longitudin•l muscle, Inferior longlbldlnal muscle, tnnswne muscle, vertical musde.

The extrinsic muscles m~ the tongue as 1 whole, while the Intrinsic musdes alter Its shape. Ellcept fur the palatoglossus, which is supplied by the VI!JUS nerve (CN )(), all of the lingual musdes are Innervated by the hypeglossal nerve (CN XJI).

\

D Unllner.l hypogioaoll netwe p•ltr Adlve protrusion ofthe tDngue with an Intact hypoglossal nerve (a) i nd with a unllmral hypoglossal nerve lesion (b). Whe"l the hypogiCJS~al ntn"e is damaged on one side, the genioglossus

musde Is paralyzied on the lffected side. As a result, the heillthy (Innervated) genioglossus on the opposl~ side domiNtes the tongue across

the midline tow~ VIe affectrd side. When the !Dngue Is protruded. therefore, It d~b!s tow~ rd the paralyzed slde.

•

ApadiDnguo

b

105

6.3

Tongue: Neurovascular Structures and Lymphatic Drainage

• A Nerveund-lloltfletDngue • ~ft lateral view, b view of the inferior sur· f.lce ofthe tongue The tongue Is supplied b¥ the lingual arh!ly (from the maXIllary .artery), which diVIdes Into its l!!rminal br~ndtes, the dHP lingual ~rtery and the sublingual artery. The lingual vein usually runs parillel to the irtery and drilns Into thetntrmoi}Ugllklrwtn. The lingual mucosa receives il$ $DmQfosensory innervation (sensi· tMty to thermal and actlle stimuli) from the ltnguol rtMil'. which rs i branch of the trtgeml· nal nerve's mandibcJiar division (CN V~. Tbe lingual nerve transmits flben from the chorda tympani of the f.lclal nuve (CNVII). imong them the .afferent taste ftben for the .ilntel'for two-thirds of the tongue. The chorda tympani aiJO cont
Subllngu;JI iJrtl!ry

Apexoflalgue

An1:2ffor lingual glands

Frenulum

Subtngu;.l fold

--~~

Subtngu;.l

---==--'!!!!~

papilla

b

106

Deep lingual

ilrtl!ry iindwln

H ' - - - - Ungu~IIICS'IIe Sulmllld'bullr duct

HHd -

6. OnJICDVII.y

~~~-=~--G~~~

.-(CNIX}

B Somltosensory lnnll!ll'lllltlon (lefttTde) and tlste Tmermfgn (rtghtshfe}oftheton1Jue Anterior view. The tongue receives Its soma!DsfnSOfY Innervation (e.g., touch, pain, thermal sensiltlon) fn:Mn three crllnlal nerve brindles:

• Lingual nerve (br•nch of mllrldlbular nerve~ V1 } • Clo.ssophllryngeal nerYe (CN IX) • V..gus nerve (CN X)

Slilmental

..

lymphnodeJ;

/

Three crani;ll n~rves llbo convey the tam fibers: CNVII (facial nerve, chordatympanQ, CN IX(glossopharynge..l ~~~ne),llnd CNX(Yagus nerve). Thus, a disturbance oftaste sensation Involving Ule anterior two-thirds d the tongue lndkates the presence of a f.adlll nerve lesion, whereas a disturbance of ucble. pain. or thermal senwtion irldicates a trigeminal nerve lesion (see also pp. 75 and 81 ).

\ - - jugl.fafao:lal

wnous)lnctlan

- - - - lntl!mal )!gular win

>---- jugl.far

•

lyn'Cih nodes

c t¥mphlltl'c drlllnege of the tanguund oral fl_. Wt lab!!ral view (a) lind anteriarview (b).

The lymphatic drainage of the tnngue and oral floor Is medlawd by submental and submirldlbular groups of lymph nodes that ullfmately drllln Into the lymph nodes ilong the Internal jugular vein (a,jugular

b

lymph nodes). Beausethe lymph nodes recellle dr.alnage&om both the ipsilab!!ralllnd conbr.alaterlll sides (b). tumor cells m..y bemme widely dlssanlnilted In this region (for example, metastalk squamous «II carcinoma, especially on the lateral bollfer of the tongue. frequently mebstasi'Zes to the opposite side).

107

Head -

6.4

6. OraiCiwfty

Oral Floor

bmus of monclble

Angltof ----,'11~ mandible

•

HyaglaliSW

--f----"'-------~

~o~d--~----------~--· Dlgastrtc. _

_ ___/

antnr belly

A Mulldauflheol'illftcao Supertorvtew(1) lind left lolltleral vlew(lt). The oral floor is formed by a musrular sheet that stretdles between

the two rami of the mandible. This sheet consists of fvur mUKies, all vf whldl are lot.itEd above the hyoid bone and lire thus collecltvely known as the su prahyold muscles: 1. Mylohyoid: The muscle fibers from NCh side fuse In ll median raphe (cowred superiorly by the geniohyoid).

101

CoiYiectiYe-Cissue sr..g

2. Genloh)'uld: mengthens the central portion of the oral floor. 3. Dl§lllstrlc: The o1 ntertor belly ofthe digastric Is lot.itEd In the orlllfloor region; Its postertor belly llrtses from the mastDid process. 4.. Stylohyoid: arises from the styloid proceu. Its tendon is perforllted by the lntmned~ tendon vf the digastric. All four mu3da participate in Kti~ opening of the mouth. They also elevate the hyoid bone lind move It forward during swllllowlng.

HHd -

'11-~:---

6. OnJICDVII.y

Inferior alwolarneM O!orda tymp.1111

Subrnandbular ganglion

Dl~c.

'-'1!ohyold

antl!rforbelly

T!IQemlnal oan91on Clenlcu~

gangjlon

c MIStold

Mandbl.far dMslon

aels

.~f---

Dlgam!c,

()Oiteforbelly

b

Faclalne~~oot.

Fadal~

st)lolr)oold brwu:h

dljil!ltric b111nch

8 lnMIYol\fon of the ol'il floor muKfi!S a 1St lilterallltew (right half of the mandible VIewed frcm the medial side). b Sagittal section thrac.rgh the foght pl!tnlus bcule at the lew! d the miiStold proan and mastoid air cells, viewed from the medial slcle. c Left later.;rllllew. The muscles of the or.al floor have a ccmplex nerve supply (differ· ent br~nchial arm derivatives) with ccnlributions fram three dilli!!rent

nerves:

a The derfvatllles of the mandibular arch (mylohyoid, antenor belly of the digastric} are supplied by the mylohyoid nerve, a branch of the mandibular division (CN V3}. b The derllla'liYeS d the second br.;rnchlal .;rrch (postenor belly d the digastric. stylohyoid) are supplied by the facial nerve. c Thegeniohyoid (and the thyrohyoid) muscles a resupplied bytheventral r;rml of C1 spinal nerve, whlch tra~l with the hypoglossal nerve.

109

6.5

Oral Cavity: Pharynx and Tonsils

A waldeyer's rTng Pom!rl~r view of the ~pened pharynx. All the components of W..lcleyer's rfng c;m be SHn In this VIew. Waldeyer"s ring ls composed of immunocompetent lymphatic tissue (mnsils and lymph follicles). The tonsils are "Immunological sentinels• suJTOundlng the passageways from the mouth and nasal caVIty to the pharynx. The lymph ~!ides are distributed over ill of the epithelium, showing marked regional wriilttons. W..ldeyer"s rfng consists of the follOWing structures:

• The unpi!lred pharyngeal tonsil on the roof of the pharynx • The paired pal;atinetonsils • The llngu..l tonsn • The paired tl.ibil tonsils (tonslllae tubir1ae). whkh may be thought of as lateral elrtl!n· slonsofthepharyngealtonsll • The paired literill bands

Pharyngeal - ---::::;,....;;.""l!

"'=::'"'-'".......- - lloofof pharynx

tonsil

>--"f-,-7--

Tubal tonsil

~c1f"ue

oflmral bands

----,--..

(u"'ng"'

IT-!::~---;---

Palatine tonsl

"---- -+- - Ungual

pharyngeal fold)

tonsl

Tons11ar fossa U\11111

Palatine

tonsil

a

I Pill.nlne ton Ilk: loc.1tlon ;md ibnomnil enlarg111111nt Anter1orllfewofthe oril caYity. ;a The Pililtlne tonsils occupy a sh.1llow recess on each side, the ton·

slllarfossa, 'Which Is locilted between the anterior ind posterior pillars (palatoglossal arch and pi!latopharynge.al arch).

110

b

c

b 01nd c; The Pililtlne tonsil is examined clinically by placing a tongue

depressor on the anterior pillar ind dlspladng thetonsllfrom Itsfossa while a second Instrument depresses the tongue. Severe enlargement of lfle p;~latine tonsil (due to viral or badl!tial infection, as in tonsillitis) may slgnlflcantly narTOWthe outlet of the oral callfty. causIng difficulty In swallowing (dysphagia).

Choana

---+.~~----~·~ phoryng..l

tonsil

..

a

C Phllryngol tonsil: loutton and abnormal enlargement Saglttill section through the roof ofthe phill'yrwt.

often evoke <1 helghtmed Immune response In the lymphatic tissue, auslng "adenoids" or "polyps.") The enlirged pharyngeal tonsR blocks the choanae, obstructing the nanl airway and fordng the child tD breathe through the maulh. Since the maulh is 111en constandyopen during resplr<~llon ill: rat. an eJCPerlena!d examiner can quleidy diagnose the aclenoldill condition by vlsuill Inspection.

• l..oabi:d on the roof of the pharynx. the unP'ired pharyng~l tonsil an be examined by means of postErior rhinoscopy (seep. 119). It Is p;~rUculilrty well developed In (small) chlldren ;mel begins to regress at 6 or 7 years of age. b All enlarged pharyngul tonsil Is -vay common In preschoo~age

children. (Chronic recurrent Nsopharyngeal lrnctlons ill: this age

llll!!plr.I!Dry

Nanla!mln!ZI!d stntllled

fS)Ithelum

>qUIITICIUS Olllthet~m

~

!

. . -..:.

• #'• •• • '

•

..

I

5e(l)ndary fcllldes

D Htlbllogy of the lympMtlctluue ofthearal cntty and plwynx

Because of 111e dose anatomical relationship between 111e epitheJium i nd lymphatic tissue. 111e lymphatic tissue of W.;ddeyer's rtng InIso des· lgnated lymphoeplthellal tissue. il

"'"""oeplthellill t!Aue. Lymphatic tissue, both orga nlzed and diffusely distributed, Is found In the lamina propria of all mucous membranes and is known as mucosa·associatl!d lymphatic tissue {MALT). The eplthellu m acquires a looser texture, with iibundant lymphocytes il nd mi1Crophages. BesJdes the wel~deflned tonsils. smaller miiKUons ~ lymph follicles may be found In 111e lateral

tf j

OlPtS Stcandary full ida

I

- - - - - Cannec!Mlluueapsule

Rmln•nts ohlaughed

c

eplthellalalk

bands (salpingopharyngeal folds). They extend almost vertically fram the lmral wall to the posterior wall of the oropharynx and nasopharynx. b S'tructure of the pharyngaltand. The muCOSill surface ofthe pharyngeal tDnsll Is r~lsed lniD ridges that greatly Increase Its surface area. The ridga and inb:NtJ1ing crypts are lined by cilimd respiratory epithelium. c S'tnlc:ture of tile Jlll'-tllll! taniiL The surf•ce area of the p;~liUne IDnslllslncreased by deep depressions In 111e mucosal surfxl! (creating an Ktive su rf'Ke are<~ as la'lJUS 300on'). The muC05ill is covered by nonlcrr.rtlnlzed strilt!fled squilmous epithelium.

111

6.6

Salivary Glands Au:us.«y

parotid gland

A Mi)orAIInrygl;mds L
b

112

Facial ar11try

Submandibular

lllldwfn

dand

HHd -

6. OnJICDVII.y

~LYfi!~=---:-- ublal

glands

8 Mlnornllv;uyglands In addltton to the thrl!e ma)or p;~!red glands. 700-1000 m1110r glands also se
C Bimanual ellilmln;atton of tile s;allwilny gl;ands The two s.illllary glands of the mandible. the submandibular gland and sublingual gland, and the adjacent lymph nodes are grouped around the mobile oral floor, and so they must be palp;~ted against reslstmce. This Is done v.tth bimanual examlna!lor1.

Parotid

Superfldal tl:mpo!'
tllmor

<~~<~ndwln

I

J I

I ( Jugular

lymph nodes

I

HypogloJsal nerw Slbmand~

I

~}

Fiitlalnsw

\

\

blllarl)mph nodes

P.rotld pluus

Atdalnsw

ln!J!ITIII Jugula-vein

D Spretd of mlllgn1nt p1rvtld tumon 1lo09 ulltomkll ~ Malignant tumors of the parotid gland may directly ln11ade surround· lng structure.s (open arrows); they may also spread vla A!glonallymph nodes (solid arrows), or spread systJ!micllly (metastasize) through the vascular system.

Parctld gland. d~p;rt

51:2mocleldomastoid

E lntragl1ndul1rG1urse of tile f.lldll nerve rn the p1rvtld gllnd The facial nerve dMdes Into branches 'Within the p;~rotld gland (the parotid plexus sep;~rates the gland Into a superflclal parund deep p;~n) and is vulnerable durirlg the surgical removal of parot!d tumors. To preserve the facial nerve during p;~rotldectomy, It Is flrst necellSary to loc
113

Hettd - - 7. Nose

7.1

Nose, Overview

""-'-...;_-~:----.-""---:-"r--- ~lcular

Mldde - --+...;;-.nasal concha

plate of

7-':......:=--:-::-=- -

ed!mold bone '-\,_;::-,~~~~~-

lnfr410rtl1<11nenoe

- --:--:---:---:f-- - M;aclllarysl'nUI

CJrthuklous

----''o--~~..,....:.=-----7.;.-.::~­

oiiSolll~

--~---~~~~--~~ nasal concha

~~--~~L-~L___ ,~

nasal mea1US ~-.......-'~,....-------".------

Alwdar proaem;

•

I

Tongue

Onllcl1111ty

b

A OW!rvlew afthe nll:lf! and p1ranaul sl'nules Coronal section. antel1or Ylew. b Transverse section. superlor11iew. The re;rder Is assumed to be famllrarwlth the bony anatomy of the nas.ill C.i111lty(especlallytlte openings of the various paSs.ilge.s ~the nas.il amchae, seep.19ff). The nas.ill cavities and par.anas.ill sinuses are arranged ln paii'J. The left and right nasal c<~Yit!es are separated by the nas.il septum and hive an approximatEly triangular shape. Below the base of the triangle Is the oral cavity. The follo"fng pained paranas.il <11

sinuses are shown in the drawings:

114

• Front.'!l sinus • Ethmoid ails (etflmold sinus•) • Mildllary sinus • Sphenoid srnus The interior of each .sin LIS is lined with ciliated (seep. 118).

respir<~tory

epithelium

• The term •ethmoid sin LIS• hilS been dropped from the l;atest anato-

mical nomenclature, iltttough It Is stlll widely used by medical practitioners.

HHd - - 7. Nose

Sphenoid

31nus

1\las.il - --."'"---,......--~

s.tj)tum

Phorynllt
o~dpharyngo­

t)mp;uict\lbe ..,..,_.......,~ Oensd m

Soft palm, palallneseptum S9henokl

sina

Umennasl

b

B Muco:u of the n.~~~l arutty

Middle niS.lllax1cha ~~----,::.....;:;'---Cho;Jna

("I)OStA!rior naris')

P.alatoph;lr)'ngeal

Tongue btlse - --':-oojol.,_,_;. wlthltngUII

tonsil

'""

,.;;r--=--.,.--- tM.I~

a Mucosa af the nasal septum, parasagittal section 'riewed from the left slde. b MucoJa of the rtght lmrosl nasal wall. viewed from the left side. c Posterlorvlewthrough !he cho;mae intD the nasal c.avity. While the medial w.rll of the naJal Ci!VIty ls smooth. Its lmrill wallis raised Into folds by the three conchae (supenor, middle,. .and inferior conchil). The~ incre
115

Hettd - - 7. Nose

7.2

Nasal Cavity: Neurovascular Supply

MediillnaAI

--~~~~

bn~nches

llleue~·s -

-f-----.iNfc-'*'?f.,.f\.

area

A Vessels •nd nerves ofthe .-.1 seJ~Wm wttfl tfle ~ ~

Pilras.1glttal section, viewed from !he left ski~. The .-.rteffal supplyofth~ nill!al $eptum Is of partiCIJiar dlnkallnterest In the dlagn0$1s .mel treatment of noM!blftd (see C).

...

~

~or---~~~

dhmoldal al'tl!ry Mddle---.,&.:..,.,., nas.al alndla Pom!rlof~orn.1ll.11---:z~

brand!K,Im!'al pasllerlof nas.lla11!ffes

~~~~.....-- Oesarul-.gp.Ma11n~artl!ly,

g!Ntltr palatine nerve, and le:lut palatine neNes

lnflrlor nnal co nella

U\lula

B Ytsselund nerwsaftflelfghtlltil!ral n~~~alwal Left l~teral view. The ~rntop~l~tine ganglion, an import~nt relay in

tfle par.ssympilthetlc nervous systEm (seepp.81 and 101), hils bftn expo~ herebypartlill re~lon ofth~sphenold bone. The neNeflbers arising from It pill!s to the small nill!al glands of the nasal coDChae, entering the condl;!e from the po$terior side with the blood ~"els. At

116

the level of the superfor concha, !he olfactory fibers pass thrcLJgh the cribrifonm pl;ate to the olf.lctory mucosa. The n;~salwall is supplied frvm above by tfle two ethmoidal arteffes, whldl arise from the ophthalmic artery. It Is supplied from behind by the later.~l postertor nasal arteries. which arise frcm the sphenopalatine artery.

HHd - - 7. Nose

Thefiguresbelowdepictthdunctianal groups of ~rtertes and nerveJ supplying lfle nawl cavIty. As rn ~ dlssecUor1, the septum Is displayed flnt. followed by the lateral wall.

c

Artertes ofthe 111111 ~m left lateral view. The ft.JSels of lfle nawl septum arise from branches of the exter· nal ;md Internal e<~rotld ;uunes. The ;mtenor p.art of the se¢llm a»ntlins a highly vascularIzed a~ e<~lled Klendbach's area Undlcmd by color shading), which Is supplied by vusels from both major i111:erles. This ilrt'a Is the most mmmon slt2 of slgnlfle<~nt nosebleed.

~btach's

- -++-..-; ,;:;

lftl1l

Olf.xtory

CrtH!fomlplm

bulb

afetflmoldbone

D Ncm:softheniAI septum

Ophtllllmlc

left lateral view. The nasal septum re«llles

dvtsfon

Its sensory lnneN.atlon from branches of the

trigeminal nerve (CN V}. The anterosuperior p.art of the se¢llm Is supplied by branches of the ophthalmk dMslon (01 V1), and the rest by brioches of the maxillary dMslon (CN V1). Bundles af olfactory nerve fiber$ (011) arise from receptors In the olfactory mucoJa.

...;;!-::::...._-

Trigeminal 91f19llan

c.dlaglnous naniS1!ptum

Medial supetlar ~ornanlbr¥lches

(maldlarydMsiOn) VGmer

Mallia

Nasop;lla!lne ntNt

~arna11c

proa!.SS

t-.;;o..::::::,..~;.,....- ~

~----"'-l''lo'

l)llitflll!

!llnglion

Inferior pomrior nlllll bnlnch!s

l.atl!
E

Artertesaftfu~rtghtlltil!nl n•sal-11

Left lateral view. Norethe v.ssCIJiar supply from the branches of lfle Internal c~rotld ar1:ery (from above) arid tile external e<~rotld ar1:ery (from behind).

I!Umll nasal

Inferior

brandies

ni!WIICIXlchl

F NenltSaftMrfghtlatenl n1saiWIIII Left lateral view. The nawl wall derives its sensory innervation from brancheJ of the ophthalmic diYislon (CN V1) and the rnaxlllary dMslon {CN V:z). Receptor neurons In tile olfactory mucoJa send their axons In the olf.actory nerve (CN I) tD the olfactory bulb (seep. 179 E).

117

Hettd - - 7. Nose

7. 3

Nose and Paranasal Sinuses. Histology and Clinical Anatomy ~--Kinodlll·

belling epith'!!IIIICII!Is

_ _..:..___,,.,.--- -

-

A hnctlom•lmtesofU!emiiCDSillntfll!nuOII c;Mty Coronal set:Uon, ;mtertorvtew. The 11Jnction of the nasal mLJCosa is tD w.lnn and humidify the inspired air. Thlsls accomplished by an Increase of blood flow through the mu· cosa (seepp.S9 and 61), piKing It In a congested (swollen) mte. The mucous membranes are not simultaneously congi!SU!d on both sides, hOWC!IIer, but undergo a normal cyde of a~ngestian and decongestion tf!at lasts approxlmately 6 hours (the right side Is decangested lr1 tfle drawlr~g). Examlflatfon of !he nasal av1ty nr1 be fadlltlted by first ad· ministering a cleconge.sunt to shrink the mucosa, roughly as It apJ)elilrs here on tht- lt-ft sidt-. l'fon!al

sinus

Etlmold

Sptlenold

s'rlus

sinus

.:.....;..~~- Fbrouslamln;~

prop!la

NISII~m.

8 Hlltologyof the niiSal muCOR

The sumce of the pseudostratlfted respiratory epithelium of the nasal mucosa consists of kinDCilia-be..aring cell$ and goblet cells, which secrete their mucous Into a wamy film ar1 the epithelial surf.!a. Serous and seromucous glands are embedded In the connectfvetlssue ;md also release secretions Into the superficial fluid film. The directional fluid flow produced by tht- cil~ (see C and D) is an importlnt companent of the nonspecific immunt- response. If coordinated beat:!r~g of tfle dlla Is Impaired, the p;ll:lentwlll suffer chronic recumng Infections ofthe resplrlltDrytract.

Oslfum

\

Pomrtar Willi

offronl.llsfnus

- - - 1\lasopharynx

Medlalw;ail of m.lillhrysfnus Eltlmold

b

C Nannnll dratnage of t«rl!tlant from tfle piNIIIUl tlMil

l.dt latera111iew. The beating dlla propel the mucous blanket over the cilia and through the swaiiOI!tt'd.

choar~a

Into the nasopharynx. where It Is

lnti.ndbllum

D Dlredlon afdlary bdtfng and fluid f l - In tfle rtght mullllryslnuJ 1nd frontal sTnuJ SchernaJSc coror~al sections of the right maxillary sinus (
tides and microorganisms thlt ire tripped In the mucous layer. If the ostium Is obstructed due to swelling of the mucosa, Inflammation may develop in the af!Rted sinus (sinu!itiS). This oa:urs most commonly in the ost!omeaul unit« the maxillary ~lnt.IS-dhmold DSI:!um (see pp. 20 ;md 21) (ifter St
111

HHd - - 7. Nose

F IE'ndoscopy of dta mulll;uy llnuJ

Anterior 1/few. The maxillary sinus Is not ilc:cesslble to direct Inspection .md mustthe!'efore be examined With an enclosco~. To enter the maxlll;lry sinus, tfl~ ex.;rminer pierl%5 the thin bony wall below the inl'l!rior cond!i wlth atroc
a

Anterlet ond ~or

Ophtlwlmlc

dtlmoldal arteries

artery

• PhlryngNI ton.1l1 flioste!1or m1 rg'n ofS1!pCIJm

()phthalmlclrter)> Dorsaln~

lrtery

lnf'ellor ~

Anguln lrter)> Facilllll'tl!l')'

b

I.M.fa

E AntertDr and postertDr rfll-py

a Antllrtorrfll.-pybaprocedureforlnspectlonoftflemsalcavlty. Two different positions (1.11) are used toensure that all oftile anterior niiYI a~~tty Is examined. b In p-rtor rfll.-.:opy, the chD.'!nae and pharyngl!ill b:lnsil ane <~ccellSible to cllnle
b

An!J!rletll1d poMicr

tthmolclll 11tsfes Orlllt

lnfraorb!t.11 foramen

G Slta d arterllll llgalfon fordte tratment of severe nosebleed If a severe nosebleed e
scope.

119

Hettd - - B. Eyuntl Orbit

8.1

Eye and Orbital Region

SUpr.IICirbllalartl!ly

Dorsal nasal

andne~~~e

arlltryandwln

lnfraorbltllnln'e and arlltry

~palpebrae super~orts

Fad'al artl!ly
Orblcularts a run. palptbral part

Angular artl!ly

Medial palpebral

and vein

tgament

Nasalis

alaequenasl

SUpraarbltllartl!ly SUpraSuperior and neM !rodllear ntNe obi~

Trochlea

Superior

tn.1l musde Orbital SllptUm

SI.Ciftlor

~~1-\:~r- ophtflalmlcwfn Laafmalgland, Olbllalpart

- - -+ --li/1

'Hrii"r- - - ucr!lllill S.IC

Lilatnal gland,

_ ....,.~~-Dor5aln~

palpdlral part

erteryend"'ttl

Lil11eral palptbral ligament

lfAI'\r.~-----=:--::---

tar.sus

b

120

Angulararury andwn

SUperior

Inferior tarsus

lnfraolbltll neM andl11121y

Fadalartl!ly

I.A!\Ialorlabl supl!r'lorts

A Sclperftd;ll ~nd d18p MUI'OIIiiiiCUYr structures afthe orflltill region Right eye. anttrforVIew. • Superficial layer. The arbiUI septum on the right side h;ss b~ eJq>osed by removal Clf the orbicularis oculi. b Deep layer. Anttrlor orbltoll rtructures hill/e been exposed by partial removal of the orbitoll septum. The regions supplied by the lnmnal carotid artefy (supr.ilorblt.ill artery) and ext!mol carotid artery (infraorbital artery, f.atial arlzry) meet In this region. The anastomosis between the ;mgular vein (extr.ilcranliiO and superior ophthalmic wins (ln1racranlal) creates .il port.ill of entry by1M'Iich miaoorganisms may reach the c<1vemous sinus (rlsl:of sinus thrombosis, menIngitis): therefore It Is sometimes nec:ess.ilryto ligate this an;sstomosls In the orbital region, as In patients wnn extens11te Infections of the exmnal fadill region(~ p. 93). Nob! the paSS.ilge of the supr.il-.ilnd lnfraorbltoll nerws (branches of CN v, and CN V2) through the accordingly named foramina. The sensory function of these two trigeminal nerve divisions can be tested at these nerve exit points.

8 Surhcun;rtomyoftfleeye Right eye, an1l!rlor VIew. Th~ measur1!1Ylents Indicate th~ Meith of th~

normal p;dJ)C!bral fissure. It is impartlnt to rm- tflese measurl!mC!l'IU because there ine a number of diseases In whkh they ine altered. For example. th~ palpebr.ill tlssure may be -widened 1r1 peripheral f.ICial paralysis or narrowtd in pmsis (• drooping of the eyelid) due to OClllomotorpalsy.

Jmm R--Medlill : anlllus

. . .

_....:

of~lcls

"-t eyefkt

I.A!v.atorpalpsuae supe!lells

Orbit!I

SEptum

Si.pl!fler rectus Si.pl!fler

Orblallarts

co!lunctMII fomlx

oculi.

orbltollpart

Si.pl!flert3rs.ilmusde Si.pl!flerbl rsus with blrsal~ands

r..ens

Upper eyelid

Co mea

SUper'lor forniX

Iris

Olillrybody lnll!r!or tir!IIJ

OOJ!ar alnjunct~

~ha

Sden

l.owoer

lnferlcr1:3rul muscle

~·d

c Structwuftfle eyelids and CDn)unr:ttva Sagltt.ll sed!ontflroughtheantl!riororbltalc;Mty.b AnatomyGfthe

junctiva (tunica conjunctiva) is a vascularized, tflin, glistenir~g mucous membran~ !hat Is SIJbdiVIded lntDthe polpebrol con}!.rr!cfMI (see above).

CDnjunctiva. Tbe eyelid consists cllr~leo~lly of .iln outef and ifllnner layer With the fol· lowing mmponents:

fomlall a>n}unctM1. and ocular con)ullCINa. The ocular conjunctiva bar· ders drrectly on the comeal surf.a~ aDd combines -w!lh rt to form the c:on)unctfwiiHc, whose furlCtions iACiude:

• Outer layer: palpebrlll skin, 1WI!.lt glands, dllary gllloos (• modlfted $we>lt glands, Mall glands), Mili!a!OUs glands (leis glands), aDd twll siJ!ated m111des, tfle orbicularis oculi and levatxJr palpebr;~e (upper eyelid only), rn~Mted by the f.ilclal nenoe .iiOO the oculomotor nerw,. fl!SI'ectM!Iy. • Inner layer: the tarJUS (flbrous tissue plate), the superior aDd Inferior Wsal m111des (of MDIIer. !lmOOtfl musde Innervated by syrnpatfletlc fibers), the tarSil or paiJ)C!bral conjunctlll.il, and the tarsal glands (Meibomian glands).

• fllclllt.rt!ng ocular movements, • enabling painle$$ motion of tfle paiJ)C!bral conjunctiva and ocular cor~junctlva relative to e
;a

~ularbllnklr~g (20-30 times per minute) keeps th~eyes from drylfl!l out by IMnly distributing th~ lacrimal fluid aoo glandular secretions

(seep. 123). Mechanical irritants (e.g .. grains of Sind) ~the blink rt-

f/&. which also serves to protect the mrnea and con)unctMt. Th~ con-

Th~supenor .ilnd

lnli!lforfornlces .aneth~ sites ~Mlerethe conjunctllla rs from the upper and IOWI!r eyelid, respectiw.ly, onto th~ ~ ball. They ane mnvenlent sites forth~ Instillation ofaphthilmlc medkatlons.fn/lammat:lon aftheconjunctNa Is mmmon and COIII!es a dilation of the mnflJnct!val vessels resultlfl!l rn "pink eye.• Convenely,ll deftdency of red blood cells (anemia) may lessen the prominena oflliiScular marie· lngs In the conjunctiYa. This Is why the conjunctiYa should be routinely Inspected In every dlnlcal examination. ~ted

121

Hettd - - B. Eyuntl Orbit

8.2

Eye: Lacrimal Apparatus

lnfr.Joltltill fo111men A laat'mll apparat111

Right eye, antzriorview. The orbibl Hfllllm has been partially l'l!!moved, and the wndon of Insertion of the lev
122

along arteries to reach the lacrl'mal gland. The paras.ympathefk lnnerlliltion of the lacrimal gland i$ complex ($Hp. 81). The llaimll appamus can be understood by tracing the fltM of lacrimal fluld obllq~~ely downward from upper right to lower left. From the superior and Inferior punellt !he lacrimal fluid enters the super1or .and lnfertor /acrfmo/ con a· liaJ/i, which dil'l!ct the fluid into the locrimGIsac. Finally itdrains through the narorocrimal duct to an outlet below the Inferior conma ofthe nose. "Watery eyes" are a typical cold symptom caused by obstruction of the Inferior opening ofthe nasolacrimal duct.

-

NIISIII

. -: ~ ~: .

.. :

...· . 8 Dllt.rtlutlor1 of 90blat ceiiJ lr1 the cor~!WICIMI (ilfter Cllabria and Rolando)

Cobletcells .are mucous-sec:relfng cells With .ilfll!pllhellal cOIIelfng. Their secre&tu (muclm) are ar~lmportant cx:~nrt!tiJent of !he lacrimal fluid (see C), Besides the goblet cells, mudns are also secreted by tile main lilcrimal gland.

D MKh;mlc.JI propulslor1 ofthelacrfnwUUd Dutfng do sure of the eyelids, cx:~ntrac:Uon of the orblaJiarts ooull ~ ceeds In .a tempor.al·to·nasal dlreclfofl. The successiVe cx:~ntraclfofl af the5e muscle fibers prvpels the lacrimal fluid toward the lacrimal passages. Noll!: Facial paralysis prewnts clcsure of the eyelids, causing the eye to dry out.

Lipid layer, apprax.O.lJim

b

c

C Struduruf the tar film (ifter IAr~g) The tear fllm Is a complex fluid With sevetal morphologlully distinct layers, whose cx:~mponents .ilre prodOO!d by IndiVIdual glands. The outer lipid layer, prodOO!d by the Meibomian gl;mds, prvtecu the aqueoU5 middle layer of the tearfllm frvm eYapora!lng.

tnferforlaafmal C
Comncn lllalnwl

an.wlk:ulus

E ObstrudlofiJ to l.a:Tm~ll driiMge (after Ling) Sites of obstruction In the lactfmal dralr~age system car1 be located by Jrttgatlng the system with a special fluid. To make this detennlfl.iltlon, the ex;aminer must be f.amiliarwith the anatomy of the lacrimal apparatU5 and the normal drainage pathways for lacrimal fluid (see A). a No obstruction to l;lcrimal dr.rinage (cx:~mpare with A). bifid c Stenosis In the Inferior or common i;lcrlmal car~allculus. The stencsls causes a damming back aflaafmal fluid behind the obstructed site. Ill b the fluid reflwa!S through the inferior lacrimal canaliculus, ind ln cIt flows thrvugh the superior lacrimal car~alloulus. d Stenosis below Ute level of the lacrimal wc (postlilcrimal s.1c sten~> sis). When Ute enure laatmal s.1c has fllled With fluid, the fluid begins to reflux irlto the superior lacrimal canaliculus. In such cases, the lacrimal fluld often has i purulent. gelatinous appeilrince.

123

Hettd - - B. Eyuntl Orbit

8.3

Eyeball

Ocular -----,~ con)lndflla

~0~---~~~----------~~ fo:sR

tUtUS

A lhii'IM:f'Se scdlon through the ~II IUght eye. superior view. Mort of tile eyebillls composed of lhree concentric layers (from outside to Inside): !he sden, choroid, and retina. The anb!!tior p«tion of the eyl!!ball has a diffen!nt sb'ut:Wn!, howevl!r. The outllr COilt of the eye In this region Is formed by the comN (ante· rlor p«tlon of tile fibrous eDit). A'S !he •v.1ndow of the eye." It bulges foJWard while COY«fng !he strut:Wres behlfld lt. At the corneoscleral limbus, the come<~ is continuoU5 with the less a~nvex sdt1111, which is the porterlor portion of the outer coat of!he eyeb
124

The Iris shields the eye from exce~IYe light (seep. 128) and covers the lens. Its root Is continuous wllh the ciliary body. which contains the cllrary m111de for wual accommoclatlon (a tilers the refractllle power of the lens. see p. 127). The epithetium of the c1iary body pradi.IC!e$ the aqueous humor. The dllarybadyls contlnuous<~tthe ora semta with the middle layer of the eye, the dtorokl. The choroid organ Is !he mllSt highly vascularfzed region In the body and serves to regulate !he tem· per;~t\Jreoftheeyt>and tuupplyblood to theoutC!I'I~rs of the retina. Thelnnerlaywofthe eyels the ...Urlil, whlch Includes
poral to the optic disk. Incident light Is normally focused onto the fofta centra lis. which Is !he site of greatest wual acuity. The rntertor of the eyl!!bill is occupied by the vltn!DIII hum11r (vltfto~a bDCfr, see C).

Site ohttadlmentto 0111S
ba!ieofSalzmaM)

B lll!fei'II!IIICe l1'nes and poTnts on the f!111: The line marking the greatest drcumferenct' of the eyeball Is the equa!Dt. Lines perpendlaJiar to the equiltOr are ailed lllflldlatts.

Normal (emmetroplc) eye

C Vlln!oul ~ (llttn!DUl hum«) (after Lang) Right eye, tramverse sectior1 viewed from above. Slm wflere the vl1:reous body Is itt.1ched to other ocular structures are showr~ln red, and adjacent spaces are shown In green. The vitreous body subii!Zes the eyeball and protem against retinal deuchment. Devoid of nei'YC!$ and vessels, It conslm of 98:1: w.rter and 2:1: hyaluronk add and collagen. The "hyaloid canal" Is an embryological remnant of the hyaloid irtefy. For the treatment of some diseases, thellttreous body mq be surglc.llly remcwed (vinctomy) and the resulting avity filled with physiologial salfne solution.

lnddlnt

llghtni)'S

/

I

i

l.
D light refrutlon Tn a nonn1l (emmetrvpk) CJI!Ind In myopTa

n!Cius

01nd hyperopia

Par.allel rays ftom a dlsunt lfght sou ret' are norm.ally refr.acted by the CDmea and lens to a fDcal point on the retinal surf.!ce. • lrl myopia (neanlghtedness), the rzys are focused to a point,, front of the retina. • lr1 hyperopia (fal'llghtedness), the r.~ys are fDcused brhlndthe retina.

E Optlc.~l ulnnd orflltai..U Supaforvlewofboth eyes show!Dg the medlal,lateril and superior recti and the superior oblique. The optfal axis deviates from the orbital axis by 2l'. Bee! use of this disp.2rity, the point of maximum visual acuity, the fO\'e'ilcenmlls,b lateral totfle "blind spot• oftheoptkdlsk(seeA).

125

Hettd - - B. Eyuntl Orbit

8.4

Eye: Lens and Cornea

A OftMew: Posltfon ofthe le111 and CDI'Ma lrt 1M eyeball Hirtlllogical section through tbe c:cmea, lens, and suspensory ~pp~ratus of tbe lms. The nor· ~I lens Is dear and tr.msparent and Is only 4mm thick. It Is suspended In the hyaloid fos:sa of tbe vitrecus body (seep. 124). The lens is at· tached by rows offlbrils(Z!Inularflbm)tothe ciliary muscle, whose contractions alter the shape ;md focal length of the lms (!he strucwreoftheciliarybodyisshown in B). Thus, the lens Is a dyn~mlc strucwre that can dlange Its shape In response to visual requirements (seeCb). The anterior chamber of !he eye Is situated in front of the lens, and the posterior chambEr Is locatl!d b~ the Iris and the anterior epithelium of the lens (seep. 128). The lens. like the vitreoUs body, Is devoid of n~ and blood vessels and is composed of elongated epithelial cells, the lens flbm.

f'QstJ!flor

Ills

chan'b!f

a~J~ ~

lllrspillla

lllrspllab

ll:>nular flt.rs

Epltht!l\lm of dllrybody

T~ular

meshworit

Iris

Olarybody, parsplcm

I The lmnnd dlllry bodr' Posterior view. The curvature of the lens Is regulated by the muscle flbm of the annular dll· arybody(seeCb). Theo't,IQI)'bodylies between the ora smrata and the root of the Iris ~nd con· slsts of a rdat!vely flat part (pars plana) and a part that Is raised Into folds (pars pllcata). The latter part i$ ridged by ap~matl!ly 70-80 radlillly.oriented ciliary processes. wfllch surround the lens lila! a halo when viewed from behind. The dllary processes c:cntaln large capillaries, and tneir cpitnelium -retes tbe aqueous humor (seep. 129). Veryflne zonular fibers extend from the bas.1l layer of the ciliary processes to the equ.ator of the lens. These ft. bm and tne spacu between them conJtitub:! the suspensory apparatus of the lens, called the zonulf. Most of tne ciliary body Is occupied

126

Ohryprocrs.ses

Cllarymwde

by the o1i;rry muscle, a smooth musde com· posed of meridional, r.ldlal. and drcular fibers.

It arises mainly from the scleral spur (a rein· forclr)!l rtng of sdera just beiCiw 1he canal of Stfllemm), and it atbches to $trlletllres inclu· ding the Bruch manbrane qf 1he choroid and the lnnefsurf.lce of the sder.t. When the ciliary

Ora-

musde contracts. it """' tne cfloroid farward and reliiXI!S the zonular fibers. As these fibers become lax, the Intrinsic resilience of the lens causes It m assume the more convex relaxed shapethrti$ne«S$aryfoc'nearvi$ion(seeeb}. This Is the basic mechanism of visual ~ccom­ modat:lon.

ChrymuKie reiDed, zonular flben tense,

lens fbttened Llght~lndlltlnt

aa:ammod&lan

Postl!fl«

pole

Clla ry l1lll5de Oll1tra tied. :i:llOtluftberslill,

• c

lens men rouncled

lll!fei'I!IICeli'nes and dplml£~ oltfle ll!ftl

a PrtndPlll miii'Wiw lln•oftfl•lans: The lens has an antmorandpos-

tllrlor pole an am passing between the poles, and ar1 equator. The lens hili a blccrwex shape v;!th a gneater r.ildlus of curvil1llre pcster1cu1y (16mm)th.iln interiorly (1 0 mm).lts function is to tr.ansmit light r<~YS and make flne adjllltments lfl refraction. Its refractift power r;mges from 10 to 20 dlopters, depending on the state of iiCcommodatlon. The ccme111 hili .il consldmbly higher refracttl/e power of 43 diopters.

Embrycnlc nudt<4

b LTght relnu:tlound dynamics of tile lens: • Upper half of diagram: fine adjustment of the eye for for Yisfon. Parallel light rays arrtve from a distant SOCJrce, and the lens Is flattened. • Lower half of diagram: For Mrlr visKJ.n (accommodation to objects less than 5 m from the eye), the lens assumes a more rounded shape (see B). Thlsls effected by contri1Ctlor1 of the ciliary muscle (par.asymp;ltfletlc lnnerv.iltkln from Ul~ oculomaC»r nerve), causing the zonui;lr fibcn to rel;vt ;and allowing the lens to assume a more rounded shape because oflts Intrinsic resilience.

Slr.ltlfled nonb!r.!Unlzed

.squamous eplthellum

•

Ad lit nucleus

0 Growth oftfle lens and ZOMI of diiiGIIIti'IIUity (aftef Ung} a Anterior view, b la1zral vii!W. The lens cont1r1ues to grow throughout life. doing so In a manner oppo· slte to that of other epithelial stnJctunes. I.e .• the youngest cells are at thesurfaceofUielens ~lletheoldestcells.ilre d~er. Due to the constant proliil!ration of epithelial cells, which ;are all firmly incorpora1zd lr1 the lens e<~psule, the tissue of the lens becomes Increasingly dense with age. Asilt-lamp examln.rtlor1 will demonstrate 210nes ofvarying cell density (zones of dlsconlfnulty}. The .zooe of highest cell density, the embl)'on~ nucleus. is at tfle cenb!r of the lens. With further growth, it becomes surrounded by the {mil nucleus. The ln{ont!k t1UCifus dewlaps after birth, .ilnd flNIIy the adult nLtdeus begins to form during the third decade of life. The.se210nes .ilrethe b.ilsls for the morphologlul d.wlflution of c.maracu, a structural alteration in the lens, causing opacity, tmt Is more or less normal In oldage(pmentlr~10~ofall80-ye
E Stn1ctur. of the cornu The cornea Is eoftred externally by str.rtlfled,I'IOilkefatlnlzed squamous

epithelium whose bilial !;Imina borders on the anterfor llmllfng l.ilmlflil (84:Mman membrane}. The stroma (substanti;l propri;l) makl!s up approxlmately 90X of the corneal thickness ;md Is bounded on Its deep surface by the posterior limiting lamlrlil (Descemet membrane). Beneath Is a single layer of ccmeal endothelium. The come.il does have a nerve supply (for corneal reflexes) but it is not lli!llcularized and th~ fore has an Immunologically privileged status: normally. a corneal transpia fit un be perfonned without fe.ilr of a host rejectlor1 response.

127

Hettd - - B. Eyuntl Orbit

8.5

Eye: Iris and Ocular Chambers

lrfs

Pupllary lphtu:t2<

\

Ollarybody

Zcru.iar flbelll

Sclera

Lms

A loc.tUDn ofdie Trtt nd ttl~ 1nterfDr and posterfDr chambers Tr;~nSYe<W

RCtian through th~ ;utt~rior segment af the eye. superior 1/iew. The Iris. the choroid, ;rnd the dllary body at the periphery af the Iris ilre p;rrt of th~ uveal trict. In the Iris, the pigments ire form~ that determine eye color (seeD). The lrts Is an optical diaphragm 'With a central aperturt>, the pupil, pia~ in frvnt of the lens. The pupi1 is1-8 mm In diameter. It constricts on contraction af the pupillary sphincter (Jxlrv· sympal:tli!!X: Innervation ~a the oculomotor nerve ind dllary ganglion)

;rnd dl'latts on contractfol'l af the pupillary df'la1llr (sympotllettc Innervation frvm the superiarcenlic:al ganglion vi;! the internal uratid plexus). Together, the Iris ;rnd lens separm the ;rntertar c:Nmber af the eye frcm the porterlor chamber. The postertor chamber behind the 111s Is bound~ posteriarly by the vitreous body. centr;rlly by the lens. and lilt· erally by the dliary body. The anterior chamber Is bound~ anta!orly by the corne;r ;rnd postl!rtorly by the Iris ;rnd lens.

c c.- cl miDik and m,drtalls

.,

(after S
...,..,, Ught

b

B PUpl111Zl1! Normal pupil size. b m
121

c

and seNa mainly to optimize visual acuity. Norm;rlly. the pupils art> clra.lar In shipe and equal In size (3- 5 mm). Virlous Influences (llstl!d In C) may cause the pupn size to vary Ol/l!!r a range frDm 1.Smm (miosis) tD 8mm (mydriasis). Agremrthan 1-mm dlscrep;rncy of pupil size bei.Weal the right ind left eyes Is called aniSOCOIIa. Mild anisocoria Is physiological in same indiwals. 1'\Jpillary mlees such as convergence and the consensual light response are described on p.362.

Sleep. fatigue

Paln,el«rt.ement

Miotic ilgEOI$

Mydrfiltlc ~gents

(parasympathl> mlmetia, sympatholytles)

{parasympattlolytles such as atroplnl\,

sympathomlmeUcs such as eplnl!phrlne)

Homersyndrome (including p1Xllis

OoJiomotor P<~lsy

~nd
palpebl'ill llssurt>) General

Migraine alt.1dc.

~nesthe.sta.

glaucoma .tttack

morphine

D St.ructu... of the Iris The basic structural fr;amework of the Iris Is the vasculartzed stroma, which Is bounded on its deep surfac:t> by two !;ayers of pigmented lrts epfttteUum. The loose. colli!Qen-c:ontalnlng stroma of the 111s contains outer ;md lnnervascularcircles (greater and letief' arterial circles), ~lth ;are lntem~nnected by small anastomotlc;artertes. The pupillary sphincter Is an ;annular muscle loc;ated In the stroma bordering the pupil. The radially disposed pupillary dilator Is not loeilted In the stroma; rather lt b composed of numerous myoftbrfls tn the lrts eplthEilum (myoeplthellum). The stroma ofthe lrts Is Pl!fll'l!ilted by pigmented connect!llssue cells (melanocytes). When heilvlly pigmented, these melanocytes of the anterior borderzoneofthestromarenderthelrlsbrown or •black.• Otheswise,. the charilctefcstics of' the underlying stroma and epithelium determine eye color, In a manner that Is not fully under-

PUpiiLlry

dilator

stood.

Anterior

Co mea

chambe"

•

Zonular flbers lrts

\

E Nonn~l dl'ilnillfll! of ;~queous humor Tbe aqiii!OUS humor (~pproxlmately 0.3 ml per ey~!) Is ~n lmpoi'Unt detznminant of the intraocular ptessure (see F). It is pnxii.ICI!d by the n~:~n­ plgmented ciliary epltttellum of the ciliary proresses ln the posm1or

chamber (appi'Qltlmatz!y 0.15 mlfhour) and passes through the pupil Into the olltl!dorchamber of the eye. The aqueous humor seeps through the spa= of the tr.lbecular me:shworic (f'Gntana spate$} in the cham· ber angle ;md enters the canal of Sthlemm (vmous sinus of the sden). through wltlch It dr;alns to the eplsderal Yelns. The dr;alnlng aqueous humor flows toward the chamber ~nglealong il pressuregradlent (ln!raocular pre$Sure •15 mm Hg, pressure in the episcleral veins • 9mm Hg) and must sunmount a physiological resistance ilttwo sites: • the pup/llofY mlstuOOi!' (between the his and lens) ;and • the trobtatlar reslstl!OOi!' (naiTOW spaces In thetr;abecular meshwork). Approximately 85% of the ;aqueous humor flows through the tr;abecular meshworlc Into the c;anal of Schlemm. Only 15% drains through the uveosderal vascular systl!m lntothewrtfcal veins (uvec.sclml drainage

F Obstrudfon of aqui!IIIKII chl111ge •nd glluCDma The nonmallntraocul;ar pressure ln adults (1 5 mm Hg) Is necessary for a functioning optical system. p;~rtly beCilu5e It maintains a smooth curvaI:IJre of the corneal surface .and helps keep the photoreceptor cells In contilct with the pigment epithelium. When glaualmo il> present (5ee D,p.127}, the intraocular pressure i$elevated ;~nd the optic nerve becomes CDnstrlcted at the lamina afbro5a, where lt emerges from the eyeball through the sder.a. This constriction of the optic nerve eventually leads to blindness. The elevated ptessure is caused by an obstruction thilt hampers the nornn;al dr;ainilge of aqueous humor. whkh c;an no longer overcome the pupillary or trabeo.ilar resistance (5eeE). One of two condiUons may di!YI!Iop:

• AaJre or angle-closure gloucomo (a), In whkh the chamber angle Is obstructed by lrts tls$ue. The .aqueous fluid c;annot dr;aln Into the ;~nterior ch~mber ;~nd pushes portions of the iris upw.~rd, blodcing the chamber angle. • Chrw1ff or open'(lngk gloucomo (b), In wltlch the chamber angle ls open but dr;a!nage through the tr;abeoJiar meshwork Is Impaired (the red b.ar marks the location of each type of obstruction). By far the most common form (approximately 90% of all gl;aua~mas) Is primary chronic open-<~ngle glaucoma (b). wltlch becomes more prevalent after 40 years of age. The prtmary goal of treatment Is to Improve thedrainageofaqueous humor(e.g., with parasympathomiml!l:ics that Induce $UStalned contr;actfon of the ciliary muscle and puplll;ary sphincter) or decrl!ilse Its production.

route).

129

H«Jd - - B. Eyetmd Orbit

8.6

Eye: Retina

No<wtsu~l

11!11na

Oplltplllrt afl'fiiM

Mltula Iuta

A Onnfew of the l'lltTN The retina ls the third, lnnl!lmost layer of the •ball. It consists mainly of a photosensitive optic port ;md 11 sm<~ller. non-photosensitive forw11rd prolongation !Allied tl!e nllllllfwcll mlnfl. The optic part of the retlnil, shown here in yell-. wries in thickness a different lo!AItlons. It owrlies the pigment epithelium ofthe UY9I tr.lct1nd Is pressed iiJ!IIInst It by tl!e lntraoClllar prewn. The optic ~ of the retina cncb
Opllc:dlslt

lrldill port of min• } Namfswl

'---------

crr.ryl"'rlof11!11n~

roll,..

suo! rdino-tile portion
130

outer layer nnrer the Kle111: the pigtrtenmllu)orr; consisting of <11 single layer of pigmented retinal epithelium (see Gil). An Inner layer nNrer the vltr~ body: the nft/RI/Io)w. comprising ,. system of re~r cells, lntzrneu rons, and ganglion cells (see at).

• An •

Bloodw:ss.!ls

l'lnerlimltfng membrane lnddl!nt

lO.Innetlimltlng membrane

., ; :

light

"L->;,--- TWrdneurons

(ganglion eels)

• ..__ _____ 9.N~n...,ll)oer

J

00 (

6

0 ex--- 8.Nudelofgangllona!lls } - 7.1nnerpleclfonnlayef 6. Nude! ofblpolaroells

l"]l~~-l~:¥.-- Amaafnecels

(lnnernudes~rla)'l!l')

9--Eibo-- Seccnd nt\lrons (bipolar cells)

5. Oula' plelClfonn layer

HolfZilnul~l

4.Nudelofphot.o~r ~Is (oub!f nudelrllyer)

l. Oula' rmltlng membrllne

Z.Proc:l!:l.sesof

Outer limiting membr11ne

I

ptlo~Dreaeptor cells

:1:~~~~~~~~~~-1.1'!gment~thellum Pigment ~tum

a

Bruch memlnne

C Strudurnfthe retlrM ;a Schematic dliiQram of the flrst three n~rons In the visual p;lthway and their connections. b The ten <~fliltomlcallayers of the ret!Ba. Ught must pass thrcugh all the inner layttsofthe reb'Ba (the layers near· est the vitreous body) before mchlng the photosensitive elements of

the photoreceptors. The dlrectfon of tr<~nsmfsslon of sensory lnforma· tlon, h-.1s Inward, opposlb! to the directiOn ofthe Incoming light. The first three neurans of thevisu~f pathway ;are foCJn!d within the ret· IBa. Stilting with the outamort neuron, they are
b

Bruch membrane

Choroid

In ;~ddition to these largely ·~rtic;al" conn~ctions, there <~re ;~ho horizontal cells and amacrine cells that functlor1 as lnfmlfllrvnsto establish lateral connections. In this way the Impulses tr•nsmltted by the recej> tor cells are processed and Ol!lllfiW!d lM'IIIe still Within the retina (srgnlll convergence). The rctiBal MfJkr cells ~re gli;al cell$ that span the neur;~l layer r.-adlally from the Inner to outer limltlng membranes and create i supporting framework for the neurons. Exll!mal to these cells Is the pfg· /Milt epnllti/Um, whose b;asement membrane Is att
Celtr.JI --"-7f-+~ mlnai111J!ry

D Optk dl1k ("blind tpot") and lamlrM atbrosa

The unmyei!Bated axons of the ret!Bal ganglion cells (approximately 1 milliOn axons per eye} pass to a collec:tfng point at the postl!rior pole of the eye, the optic disk. There they unite to form the optic nerve .ilnd leave the retina th~gh numerous perforJtions in the scler;~ (l;!miBa afbroSil). In the optic nerve. these iXOns are myelinated by oligo den· drocytes. Nok the centril retlnil irtery mterfng the eye it this locat1011 (see p.132) and note the coverings of the optic nerve. Because the optic nerYe Is a foiWilrd prolongatlor1 of the diencephalon, It has all the cova-· lr~gs of the brain (dura mater, ar<~chnold, ;md pia mater).ltls surTOunded by a subarichnold space that cont
Blood

Bruch

~s

membrane

Choroid

E Mllcullt luu. end (owe.a central Is Tempor.-alm the optic disk Is the maalla lutea.llllts cenl:ef Is a funnelshaped depression apprOidmately 1.5 mm In dlamel:ef, the fovea c:entrlllfs, which Is the site of m.tldmum VIsual acuity. At. this site the Inner rctiBal ~ ~re he.1ped tow;~rd the margin of the dep~. so that the cells ofthe photoreceptnrs (lust cones. no rods) are dlrecdy el!PQsed to the Incident light. This arr<~r~gement slgnlflcantly reduces SGltterfng ofthe light rays.

131

Hettd - - B. EyuntiOrblt

8.7

Eye: Blood Supply

"-'~--- Antlerfar

Clltl)UnctMII al'b!ry

Iris

Lang postl!tfar

dllaryerttrfes

~~~r----~~

dUeryartl!rfes

&<,;r-;r.....,;;--

Cl!nlr.!l R!l!nal 'rtery~ndloOefn

- +----l1f---- Optlcnenoe A Blood supply af the eye

Horiz.onbl section thrDugh the right eye at the level of the optic nervi!, viewed from above. All of the arteries that supply the eye arise fnHn the op/lr:holmlc o11rty. a terminal branch of the Internal arotld artery (see p. 61 }.Its ocular br.afldres are: • Central reUnal artery to the reUna (see B) • Short posterforclllary art:ertes to the choi'Did

132

wttf

• Long posterior clllary art:ertes to the dllary body and llfs, thij supply tfle gre;~ter and le$Ser arterial circli!$ of the iris(-'«' D, . 129 • Anterior dllary arteries. which arise from the vessels of the rectus musdes of the eye and anastomose wtth the posterior ciliary ~sels Blood Is dralfled frDm the eyeball by 4 to 8 Y011ICD5e veins. which pierce the sden behlndUie equator arid open Into the superior orlnfelfor ophthalmic vern.

I Arte!HI biDad supply of tfle opUc nerve •nd optk nerve hNd l..ilter<~l view. The «ntr~l retin;~l artery, the fim

branch of the ophthalmic irtefy, enters Ute optic nerve from below <~pproxlmately 1 em behind the eyeball and coursl!l with it to the retlnawhlleglvlng off multiple small branches. The postertor cllliry artery also gives offseverill small branc:hes that supply Ute optk: nerve. The optic nerve head receivt!l its arterial blood supply from an arta!al ring (drcle of Zlnn 01nd von Halle!') formed by ilnilstomoses amoog the side br<~nches of the short pos1J!r1or dllary arta!es and central retinal artery.

k-7~--Long

~~~~:i~~~~~~

~...,~-----=----:

po~

dlllryaM!es

Ondeofllnn l••dwn Hallet)

-

Nasal

• C Ophthllmcmopfc Ulml'nltlon of the opUc funduJ Examination te<:hnlque (direct ophtftilmoscopy}. b Normalippeir· ance of the optic fundus. In dil'l!ct ophthalmoscopy, the follt!Wing structures of the optic fundus can be dlrectlyevaiUited
;a

• • • •

The condition of the retina The blood vessels (partlculirtythe central retinal artery) The opttc disk (where the optic nerve emerges from the eyeball} The macula lutea and fovea untralis

Because Ute l'l!tlna Is transparent, Ute color of the optlcfund~ Is dieter· mined c:hie4!y by the pigment epithelium and Ute blood vessels of Ute choroid. It Is unlfomnly pale red In llght-sldnned persons and Is consld· erably browner In darlc-sktnned persons. Abnormal detachment of the retina Is usually associated with a loss of retinal transparency, and the

po~

dlllryaM!es

~~~~~~~~~~-SMrt

Ten'90ral

b

retina a$SUmes a yellowish-white color. The central retinal artery 01nd ilr· tenes hiM! a brighter red color and a smaller caliber than Ute veins. This pn:Mdes a means for the early di!Uction of vascular c:hanges (e.g., stz. nosls, wall thickening, mlcroaneurysms), suc:h as those occurring In dlitbet:es mdll~(dlabetlc retinopathy) or hyperten.slon. The optfc:d/slcnormally has sharp margins, a yellowo()range color. and a central depression, the physiological cup. Tilt- disk is subject wchangn in pathological conditions such iS elt'Vited lntricrinlal pressure (papflledema with Ill-defined disk maf!!lns). On exilmfnatlon of tfle macula Meo, wltlch Is 3-4 mm tl!mpor~l to the optic disk. It can be seen that numen>US branc:hu of the central retinil ~rtery radiatl! IJ:IWard the m;~cula but do not reach Its center, the fovea centralls (the fove<1 receives Its blood supply from Ute choroid). Acommon ilge-related dlseil5e of the m;~cula lutea Is macular degeneration, whkh may gr.adually lead to blindness. ~~eln can be distinguished from each other bytftelrcolor ind caliber.

133

Hettd - - B. Eyuntl Orbit

Orbit: Extraocular Muscles

8.8

Trochlea

Superior oblique

Inferior ---'-"'r--

-i"'

n!clus

l.oltler.ll n!CI!Js

lnfelor n!CIIJS

lnftrior oblique

• A loc.ttfon ofthe o.tnDCUiar musdts (extJtnsTc• musdts) Right eye, superior view (1) and ;~~riorview (b}. The eyeball Is moved In the orbit by four rectus muscles (superlor,lnfe· rtor, medial, and latEral) and two oblique musdes (supertor and lnfertor). (lnnt~v.~lfon ~nd direction of mOYements ~reshown In Band D.) The superior oblique ariM!S from the sphenoid bone ;and tne inferior oblique from tne medial orbital margin. The four rectus musclu arise from a ll!ndlnoll!i rtng around the optic canal (common tendinous rtng, common annular tendon). All of the extr.aocularmusdes insert on tne sclera. The ll!ndon of lnserdon of tne superior oblique flrst passes through a

nodus

b

tendinous IDCp {b'Dchlea) attadled to tne superomedial orbital margin, which redirects It posteriorly at an aa.rte angle to Its Insertion on the temporal aspect of !he supertor surface of the eyeball. The fl.lnctlonal competence of.illl six extraocular m~~Scles .ilnd!heircoordinated Interaction .ilre essential In drrectlng both eyes tllw~nllhewual target. It Is the task of the brain to proass tne two perceived retinal images in a WOJY that provides binocular visual perception. If the coordinated actions of these muscles are Impaired, due, for example, to the paralysis of one e)'!! m~~Sde (see E), the visual aXIs of one eye ~II deviate from Its normal positi~n ;and the patient will perceive ;a double image (diplopia).

Superior oblique

Superior Oculcmotor nerw

n!clus

Trodde.or

-

Ub!1111 n!Ciul

Internal c.orolldartl!ry

lrhrlor cblique

AbWa!lltlli!M!

lrhrlor n!Ciul

Superior

ortltillfl!.5ure

Inferlor Olblbl f!S51.ft

Mllldlary ~_,us

8 lnneiWtfon of the extr.loallar muscles Right f!fe, la1Jel'al view ~lh the tl!mpor~l W.illl of the orbit rem<M!d. Exa!pt for the superior oblique (b'Dchlear nerve) and latzr.ll recllls (abducent nerve), the oarlar muscles (superior. medial and Inferior rectus and Inferior oblique) are supplied by the oarlomotor nerve. After em erg-

134

lng from !he brain stem, cranial nerves Ill. IV. and VI ffrst passlhrough !he ciM!ITious sinus {or Its latl!r.al wall, see A. p. 138), 'Where they .are In dose praximity tD the internal carotid artl!l'y. fn:lm !here they trawne the superlorortltal&sure(seeB. p.138)toentertheorbltandsupplythelrrespedjve muscles.

Head - - B. E)"! and Orbit

C Function and Innervation of the extraocular muscles Right eye, superior view with the orbital roof removed. The lateral and medial rectus mus-

des have only one primary action and one direction of pull (a, b), while the other muscles have secondary actions and directions of pull (c,d).

.t.t.t .t.t.t ln~lon

l'ltiMry 8dlon

Second.-y Ktlon

a Lateral rectus

Abduction

None

Abducent neM! ((]\j VI)

b Medial rectus

Adduction

None

OculomotorneM! (CN Ill), Inferior branch

c Superior rectus

Elevation

Adduction and

Oculomotor neM!

medial rotation

((]\jIll), superior branch

Muscle

d Inferior rectus

Depn!SSIOn

Adduction and lateral rotation

OculomotorneM! (CN Ill), Inferior branch

• Superlorobllque

Oepn!SSIOn and abduction

Medial rotation

Trochlear nerve (CNIV)

Elevation

Lateral rotation

OculomotorneM! (CN Ill), Inferior branch

Inferior oblique

and abduction

I

b

c

E Oculomotor palsies

Superior rectus

~~~ ~ ~~~~ ~ ~:~' Superior oblique

Inferior 11!ctus

Superior oblique

Up ond 1D the r1ght

-

UpandiDtheleft:

~

~ lnfer1orobllque

Superior ""tus

Tother1ght

~ --=----Lateral rectus

/

~

~ 'Superior 11!ctus

Inferior oblique To the left

--

~

Medialll!ctus

Medial rectus

~ --=-Lateral ""tus

Down ond ID the left

Down ond ID the r1ght

1\ Superior oblique

Inferior rectus

D The siX cardinal directions of gaze In the clinical evaluation of ocular motility to diagnose oculomDIDr palsies, six cardinal directions of gaze are tested (see arrows). The muscles that are activated In each direction and their cranial nerves are shown schematically for both eyes. Note that different muscles may be activated In both eyes for any pardcular dlrecdon of gaze.

Inferior rectus

Superior oblique

For example, gaze to the right Is effected by the combined actions of the lateral rectus of the right eye and the medial rectus of the left eye. These two muscles, moreover, are supplied by different cranial nerves (VI and Ill, respectively). If one muscle Is weak or paralyzed, deviation of the eye will be noted during certain ocular movements (see E).

a Complete oculomotor palsy on the right side. b Trochlear nerve palsy on the right side. c Abducent nerve palsy on the right side (shown in each case on attempted straightahead gaze). Oculomotor palsies may result from a lesion involving the nucleus or course of the asso· elated cranial nerve or the eye muscle itself (seep. 72). Depending on the muscle involved, the effect may be a deviated position of the affected eye or diplopia. The patient attempts to compensate for this by adjusting the position of the head. a In cases of complete oculomotor palsy, the following muscles are paralyzed (followed in parentheses by the observable deficit). Extraocular muscles: superior, inferior and medial recti and inferior oblique (eyeball deviates toward the lower outer quadrant). Intraocular muscles: pupillary sphincter (pupil dilated- mydriasis) and ciliary muscle (loss of near accommodation). Levator palpebrae superioris (drooping of the eyelid ptosis). If the ptosis is complete, as shown here, complete oculomotor palsy does not produce diplopia because one eye cannot be opened. b Troddear nerve palsy disables the superior oblique, whose action is to depress and ab· duct. The affected eye slightly deviates medially upward. c Abducent nerve palsy disables the lateral rectus, causing the affected eye to deviate toward the midline.

135

Hettd - - B. Eyuntl Orbit

8.9

Orbit: Subdivisions and Neurovascular Structures

O!tlltal Sl!lllum lnfe'lorobtque ----T-"FJ:~~ieez-i~~

A Subdlwtllan of the orbltTnto upper, mtdcl~ 1nd ICIW'el"lewll

Topographically, the orbit k diVIded lntD three levels with the follOWing boundaries:

S;rgitul $C!1Ctian through the right orbit viewed from the medi~l side. The orbit Is llrled by periosteum (perlocblt:a) and cont~lns the followIng stnuctures, which are embedded within the retro~rbltal tat: eyeb.illl, optic nerve, lacrimal gland, extr~ocular muscles, ~nd the ne\lro· vascular Jtructures th~t supply ttl em. The ret~rbit~l fat is bounded ant:erlorly by tne orbit~ I septum and tow.lrd the eyEball by a mobile sheath« connectllle tissue (bulbar fascia, Tenon's capsule). The naJTOW spaa between the buloorf.ascia and sclera is called theepiscler~l space.

• Upper lew!: be~n tne orbital ro« and tne levalrlr palpebrae superioris • Middle level: between the superior rectus and the optic nerve • Lower level: between the optic nerve and the orbital floor The con!l!nts or the dlffefent levels are listed In B.

I The three upper orbttallewls 01nd tflllfr m..tn cont.ll!nts (The sites of entry of the neurovascular structures Into the orbit are desa!bed on p. 14.) Saural.-dllled llnlcblra

Mldchlewl

136

• • • • • • • •

ua1rna1 nerw ua1rna1 ai'Ufy ua1rnal vdn Frontal nerve SuprliOrblUinem! and supratn~chlear nerve SuprliOrbital artery SuprliOrblUI win ltochlearnefW

• • • • • • • •

Branchofophthalmlcnne(CNV1) Branch of ophthalmic ai'Ufy (from Internal carotid arttly) Passes to su!)Er10r ophtnalmlc vein Branch of ophthalmic nerw (CN V1) Termlnalbranchesoffrontal nerw Terminal branch t:J oph!Nimk: amry Unites with supratrochlear wins to form angular win Nu~s of trochlear nerve In rnes«~oephalon

• • • • • • • • • • • • •

Ophtn~lmlc artery Central retinal artery Posttrlor dllary artmes N;soc~llary nerve Abducent nerw Oc:ulomotor-.superlorbranc:h Opticnene Short dllary nerves Ciliary gangliOn l'ariiS)'IIIpathetlc root sympattletlc root N;soclllary root Superior ophtnalmlcvdn

• • • • • • • • • • • • •

Branch oflntemal carotid artery Branch of ophthalmlcartlefy Branches of ophthalmic artery Branchofophthalmlcnne(CNV1) Abducent nudeus In pons Oculomotor nucleus In mesencephalon Retina (n!llnal ganglion cells) Postsynaplfc aulrlnomlc I!ben tot~ ¥ball Parasympathetic ganglion for dllarymuscll! and pupillary sphincter Presynaptic autonomic I!ben of oculomo«~>r nerw Postsynaptic ftbet$ from t~ superior ceNical ganglion Sensory tlbers from eyeball through ciliary ganglion to nasoc:lllary nene Passes Into cavernous sinus

• • • •

Oculomotor -,Inferior branch lnferlorophthalmlcvdn Infraorbital nerve Infraorbital amry

• • • •

Oculomotor nucleus In mesencephalon Passu Into ca~~emous sinus Branch of maxillary nerw (CN V,) Tenninal branch t:J maxillary arury (ext~mal ca~id artery)

Supra111Xhle~~r

al'tle'Y

Medial palpebral al'tle'Y SLCHWothlear vein

DorHI nnalveln

Anterior--~~-­

eltlmo!dai-'Y CEmnl _ ____,.,.,....._

retfrtal-ry Postlerfar et!lmo!dai-'Y

Optlc:neM lntl!mal

arotld-ry

Ophlhamic artery

Mkldle menlngealal'tlery

Ophlhamic "Win

An151omotfc blll'lth

C Brllnchas of oph'thllmtnrtery Right orbit. superior view ifter opening of the optk anal and orblt.11 rcof. The ophthalmic artery~ a branch of the Internal carotid artl!ry. It rum below the optic nerve ttl rough tne optic canal to the orbit and sup· pllu the lntraorblt.11 structures including the eyebill.

hferior

lntrnrbltel

ophthamitwln

win

fadalveln

D V.lnnf die orfllt Right orbit. lateral view with the lateral orbital Will removed ;md the

milldllary .slnw. opened. The veins af the orbit communicate wtth the veins of the wperfitial and dftl) facial re<;~ion and with the tali'CmOUS sinus (potentiil spread of Infectious pithogens).

oalomotcrnerYe.

superiorbr.anch

,_......:.,....__ _ hfnrlnxllletr ni!M!

_ _......::;.__~--....:.........:;::--:--- t.ongdlaryneM'!S

()phtllalmk - ---iiiiif-....,...- - - - - - - - '=--dv151on Trlgtmnal

new nlgemnal ganglion

Oculomotor ni!I'Vl',

S~p;rthetk

Na.odliilry

hferiorbn~nch

n10t

root

E lnnenmtonoftheorblt Rlghtorblt.later;ll vlewwtth thetempor;ll bonyw.lll removed. The orbit recelves motor, sensory and iutllnomlc lnnervitfon from four aanlal nerves: tne OCI.IIomomr nerve (CN Ill}, tne trochlear nerve (CN IV), tne abducent nenlt' (CN VI), and the ophthalmic diviJion of the trigeminal

nervt'(CN V1). The oculomotor nerve alsoc:Dmll!yS presynaptic parasympathetic fibers to the clllary ganglion. The postsynaptic sympathetic fi. befs pass Into tne orbit by WilY of the lnll!mal arctkl plexus and ophthalmic plexus.

137

Hettd - - B. Eyuntl Orbit

8.10 Orbit: Topographical Anatomy

A lntllllc3vwnDUS CDUI'M of the Cl'llnfilll niiWS tft~t entl!t' tD tfte orflft Antenor <md middle crllnlal foss.ae on tfte rtght side, superior view. The later.~! and superior walls of the cavernous sinus have bftn opened. The trigeminal ganglion hilS be1!n retncted slightly laterally, tfte orblt.ill roof hili been remOYed, and the perlorbltl has be&'~ fenesttab!d. All tfttee of the cranial ne~WS tftat supply the ocular musdes (oculomotor nerve, troch· lear nerve, and abducent nerve) enter tfte cavemous sinus, where they a~me Into dose rela!fonshlp with the first ;rnd second divisions of tfte trigeminal nerYe and with the Internal carotid ;utery. Willie !he tftlrd <md founh aanlal nerves course In !he lateral wall of tfte cavernous sinus with tfte ophthalmk and maxillary divisions of the trigeminal nerve. tfte ;rbdu· cent nerve runs directly through tfte cavemous sinus In dose proximity to the Internal carotid artery. ~ a use of ttl~ relationship, tfte abducent n~ may be damaged as a result of sinus thrombosis or an In· traavanous an~ry3m of tfte Internal arotld artery.

Perlartllta (pe!amum of lhecrblt}

oplrthamk:OII'b!ry lntl!mal a!DIId Oll'b!ry Optk:ctli5m

Oc:ulomotor ni!I'VI!'

C<M!rnaunlnus

Trlgerrinal nl!nl', motor rwt

B PostertDrwll aftfte Drtllt: mmmon tmdlnDUs rfng 1nd sites of puRge of IM!4II'GWIIaiYr stnlcbln!S tftroughtfte optk c:.111111l•nd superfDrorflltal fi'IISUre Right orbit, antl!rior vi- with mDst of tfte orbital contents removed. The optic nerve exits ~nd tfte ophthalmic artery enters tfte orbit ttl rough tfte op!fc canal. Of !he neurovasculllr structura that enter the orbit through tfte superior orbltll &sure, some enter Inside tfte common tendinous ring ;md some enter out-

side of It • Inside: ;rbducent n~. n;rsocili;lry nerve, supafor and Inferior branch of !he oculomotor nerve • Outside: superior and lnfertor ophthlllmlc Vl!in.s, frDntal nerve, lacrimal nerve. and trochlear nerve

138

Trlgemhrrl,_ smsory nJGt

Mlddlt cranllllfo:IH

SUperior obliqUe

OptlcneM!

Supe!or

oplrthamkwln

Common

undnous ring

Ophth;rlmlc arllery

Oc:ulomotor ni!I'VI!',

superlarbnrnch

=-=---T......___ SUperior ~;.::,;;,r;p-"'''

Abducent net'fl!

lnfftfor

opi!ltlalmlcwb

llftrtor

rectus

orllltl!lft"ure

Medial

brll'ldl} Supr.aorblt;al

~"..>:11~.----~~- l.irtmllnmh 'll\:~L.J-+--.....:...~----

Antsforeltlmoldal artl!ryandNrW

....-;!:~~~~-,__- I.Noltxlrpa~rae

SU~Ie~rartay --=---=~~---='l~

Pomrforeltlmoldal -....::;,;....:~~:,....-....l!r.l artl!ryandnerve

Nasodlllryne'W ~h~rnerve

superlolls

6!··· --- Llafmalgland Llafmal a1l!
Fnxrtal ne'W -~---z~-::::--

SUp raorbltll artl!ry

neM

Supr.ltrclcHmrneM!

~------nu - --=- - - - - - - !Y

;._....,...._ Superior~

=---------:-- Abducent nerve /).§~~=-------~--Superior

cphthalmlcveln

Oph!Nimlc artl!ry Oplltllln'e lnlllmale~rotld artl!ry

c ToP091'11phyoftfler1vhtorfllt: contents of the upper level Supe11or view. The bony roof of the Olblt. the periortlit.a, and the retfOoOrbit.al fat have been

remwed.

Medial

IJ!wtor palpelne SJIN!rioris

~

Superior oblique SUIN!rior ophlhamicwln N;uodr~rynerw

Shortdll•ynerws

SUpetlornectus l.aafmalgll!nd Eyeball l.aafmal arb!ry mnerYe 1..111er.al~

TJVC!IIearneM Shortpomnor dhryarb!tles

t1ferfor ophthalmkwln

OptXnerve

Abduantnerve

oa.bmotornerYe

Cllary~ngllon

D Topogl'llphy aftfle rTght orfllt: contents oftfle middle lwei Superior view. The levator palpebr.ie supel1ol1s and the superior l'l!dus have been divided and refleded bolckw.n'CI. and all f.ltty tissue has been removed to better expose the optk nente. Now; The ciliaryg~nglion is app111Ximiltely 2 mm In diameter ;rnd lies lmr;al to the optic nente approxlmately2cmbehlndlheeoyeball. The p;rrasymPJthetic innervation for the Intraocular musdes (clllarymuscle ;rnd pcJplllary sphincter) Is rel;ryed 111 the ciliary ganglion. The pDSt:synaptic symp;!thetic fibers for the pcJplllarydllator. from the superfor cefVfc;al gar~gllon, ;also p;ass through this gar~gllon.

139

9.1

Ear, Overview

Posterfar sernldn:ular

1..1teral semldn:ular

'anal

~I

• A Auditory a'ld W!ftlbullr appal'lltl.lsln 51bl a CDronal section thrcugh tile right ear, anterior view. b Main parts of the auditory apparatus: external e<~r (yeli!M), middle ear (bl~~e). and lnnerear(green). The .iludltory .ilnd Ye$tlbular apparatus are located deep 1r1 the petrous part of the temporal bone (petrous bone). The audltlny appanrt\a mn· slsts of the external ear. middle ear, and Inner ear (see b). Sound waves are e<~ptiJrecl by the exh!mal ear (au ride. see B) and triM!~ through the external .iludltory e<~n.ill to tile tympanic membr.ilr~e, which maries the lateral boundary of the mid&-. The $0Und w.wes set the tympanic manbrane Into motion. and these mechilnlcal111bratlons are trar~Smlt· ll!d by the chain of auditory osslcles In the middle ear to the ov.al wln· dow, whiCh leads Into the fnner ear (seep. 144). The ossiCIJiar chain In· duces vibl'itions in the membrane CQYC!Iing the cw;~l wind11o11. and thel't' lfl tum c.1111e a fluid column In the lnr~er ear to vibrate. setting receptor cells In motion (seep. 150). The transfonnat:fon ofsoundwaYe:Sintoelec· trlcallmpulses ukes place In the Inner ear, wllh:h Is the actual Ol!an of hearing. The external ear and middle eer, on the othc!l' hand, con'ltitute the soortd condudfon ~·The organ of balance Is the --ubular 1ppantu11,whkh Is also located In the auditory apparatus and will be de· scribed aftl!r the units that deal with tile aud:ltory apparatus.lt conurns

140

tile sl!mfdmtltlr a~nols for tile J)l!l'ceptlon of angular acceleration (ro!; tional he
ne.ss (Veftlgo).

Hf!Gtl - - .9. Ear anti VestfbuiGr Apptuorus

a RJghUul'lde The aurkle of the ear encloses a cartilaginous framework (auricular carUiage) that forms a funnel-shaped receptor for acoustic ~br...Uons.

HI+--- Postl!rtor aur'IWarartl!ry a

Aurlcularfs - ~perlor

(poslll1ar p;ll't dt81'9Qrop;ute1aJs)

1....-T---Hellcls

ma)ct

· l r ---Hellcls

minor

b

C Olrtllligundmusdesofthuurtde

a Later.!! view of the external surf.rce. b Medial view of the posterior surface of the right ear. The slcfn (remOYed here) Is closely .itpplled to the elastic carUiage of the auricle (shown in light blue). The mLIIdes of the ear are dassif.ed as muKies of facial e)Q'resslon and, like the other members of thls group. are supplied bythefadal nerve. Prominent In other mamm.ills. the aur1cular muKies are vestigial In humans, with no slgnlllcant function.

- - - Emrnalc.wt!dartery

D Artaillsupplyoftherlghturide Literal view (i) and posterior view (b). The proxlm.ill and medial portions of the laterally directed .anterior surfice of the e;~r are supplied by the anterior auricular arterin, which arise from the superficial temporal artery (seep. 59). The other parts of the ear are supplied by branches of the posterior auricular artery, which arises from the external carotid artery. These vessels are linked by extensive ana'ltomo$C!S, $0 OSJerJtiort$ on the extl!rnal ear are unlikely to compromlsetheaurlcular blood supply. The copious blood flow through the iurldecontrlbutes to temperiture regulation: dlla!Son of the vessels helpl dissipate he.rt through the slc!n. The lack of Insulating fat predisposes the ear to frostbite, which is particularly common in the upper third of the auricle. The lymphatic drainage and lnnerv...Uon of the aur1cle are covered In the next unit.

141

9.2

External Ear: Auricle, Auditory Canal, and Tympanic Membrane

Supridal p.relld lymphnDda

m: ~_,.,!!o#c..:::....-

ee.p p.relld lymphnDdeo Porotld

A Aurlde 1nd extemllludltary Anal: lymphidlc draiY~~e ilnd n!llanill.-aup• of lymph nodes

Right ear, obttque lattnl Yirw. lhe urtilaginous framework ilnd blood supply of the e1r W81! desa1bed In the p1Wious unit. The lymph~c drainage of the ear Is dMded Into thrH zona, all of which dr;in directly or indirectly Into the deep cervical lymph nodes along the lntl!rnal jugular vein. The lower zone drains directly Into the deep cavlcal lymph nodes. The ;~nterior zone first drains into the parotid lymph nodes, the posterior zone Into the mastold lymph nodes.

glond

......,!-----;:----llfgemlnalnerw, aur!DJiciBnponl

- - - Trlgemlnal.l1Urku~1111

norw

nerw

j,:-- - - ' - -

-""""l',...- -4--;:.,:__ VlgLAnO<Wand

V~u;nerwand

9oaopharyr'9NI

glossopharynogeel neve

n.erw

v

•

~rvlcll plexus. lesser ocdpltal IWIII!Sandgreata~CIIarnerw

I SeniOIY lnnen~~~tfon of the 1ur1de

Right Nr, latEral view (•) and posterior vle:w (II). The ilurlculilr region hils il complex nerve supply beCiluse, de¥tlopment:illly, It 15 locilted ilt the bound;ary betwoeen the cranl.JI nerves (p!Yryngui.Jrch nerves) and branchet of the cerviCill plt!XUS. FGur cranial ne'VI!S conbibute to the lnnerntion of the ilurlde: • Trige.minal nerve (CN V) • Faclill nerve (01 VII; the skin area thilt: receives sensory lnnerviltion from the facial nerwls not precisely known) • Glcwop!Yryngeal nerve (CN IX) and vagus nerve (CNX) 1\w branches ofthe cervical p-.. are lnvolwd:

142

Cervlcll ple>n.os, lmei'O«
b

ne.-andgrutiiurlcUuni!IW

• Lesser ocdplt.JI nerve (C 2) • Great auricular nerve (C 2, C3) Not!l: Because the vagus nerve canttibut:ts to the innervation of the external iludltury Cilnal (auricular branch, see below), mec:hanlc31 cleaning of the Nr nnal (by Inserting an aur.~l speculum or bylrrlgilttng the ear) may evolce coughing ;md naUSN. The alll1cular bunch of tfte vagus nerve passes through the m;astoid CiiNiiwlus and through a space ~n the miiStuld process and the tympanic part of lfle tempor.il bone (tympanonnastDid fissure, see p. 23) to the external uromd external a uditury C.Jnal. The ear canal receives sensory flben from the glossopharyngeal nerve through ib communicating branch with the vagus nerve.

Head - - 9. Ear and Vestibular Apporatus

Malleut

.......

5"*""' and -.....::;1-_...,:;:....;;;~

an~mong!.lds

,.....,-.'-- Laralllgamont ofmalle
~2---sr.-

audlllllyartll

,.:.;,,;.--

Hindle (lnanubr\lm)

urtlliglno... Pirtof - - - -........ - . . . . . .dimlyc.lll

l)'mpanlc

llll!mbrane

c Exb!malaudltoryCIMI, tympank ll'lll!mbnne, and tympank uvtty Right ear, coronil sectlon,anterlorvlew. The tympank membnne (eardrum, see E) separms the external auditory canal frGm the tympa nlc cavity, which Is part of the middle ear (seep. 144). The extemal auditory canalis an S.shilped tunnel (see D) thill: Is a pproxlmill:l!ly 3 em long with an iftrage diam~r of0.6 em. The outer third of the ear canal is cartlliglnous. The Inner two-thirds ofthe a nalare osseous, the wall beIng formed by the tympank part of the temporal bane. The cartllagl-

nous part In particular bears numerous sebaceous and cerumen glands beneath the kenltlnized stnrtlfled squamous epithelium. The cerumen glands produce a will:l!ry secntlon thill: combines with the sebum and sloughed epithelial tells ta fonn a protlective barf~er (D!Nmen, •earwax") that screens out foreign bodies and kHps the epithelium from drying out. If the cerumen absorbs water (e.g., water In the ear anal after swimming), it may obstruct the e~~r canal (cerumen impaction). temporarily nuslng a pardilloss of hearing.

Pa111\aafdll

'"""

Stapes

a

Ll'nbo

Antltrlar ~lleo!Jrtold

Pa11tft\U

Mall!.alarltrta ....~of llglt

D C&rlmln! Gftlw utlmill audltlxy canal

Right ear, antertor vttw (a) and transwne sec:Uon (b). The external auditory canal is most curved in its cartilaginous portion. It Is lmportint for the dlnldan to know how the ear canal Is curved. When the tympanic membrane is Inspected with an otoscope, the auricle should be pulled bickward and upward In order to smlghten the cartlliglnous part cl the ear an~~I so thill: the speculum of the otoscope can be introduad (c). Nom the pro~~lmlty of the artllaglnous anterior Will of the extern~~ I iuclltoryanaltathetemporomandlbubr)lllnt.This allows the I!Xilmlner to palpate mowments of the mandibular head by Inserting the small finger Into the outer part ofthe eu an~~l.

E lympi111IC memllri1111! Right tympanic membr~ne. lateral view. The he.:llthy tympanic membrane has a pe.-~riy gray 01lor and an oval sh1pe with ;m average surface area ofa pprOJdmill:l!ly 7s mmZ. It consists of .a lu portion, the pars /lll'«idd {Shra pnell membr;lne), and a ~ rger taut portion, the 1)0'1! tenser. whim Is d111W11 Inward at ltJ center to form the umbo ("navel"). The umbcJ marb the lower tip cl the handle (manubrium) of the m~lleus, whlmls attached to the tym pan lc membrane all illong Its length. It ls visible through the pars teRsi as a light-colored streak (malleolar sb1a). The tympanic membrant is divided into four quadrants in a clod<wise direction: anterosuperlor (I),1nterolnferlor(II), posterolnferlor (Ill), posterosuper1or (IV). The boundary lines of the quadrants are the rn~~lleolar stria and a line lnterwctlnglt perpendlcululy at the umbo. The quadrants of the tympanic membrane are dlnkally Important beause they are used in desalbing the location of lesions. The Function of the tympanic membr1ne Is revt.ewed on pp. 140and 146. Atriangular areil ofrefteded light an be seen In the anterolnfertor quadrant afa nonnaltympanic ~br.me. Tht lotation cl thi' •01ne oflight" is helpful in ~alu­ atlng the tension ofthe tympanic membrane.

143

9.3

Middle Ear: Tympanic Cavity and Pharyngotympanic Tube

A The middle or and auodll:led stftlctui'I!S

Right petrous bone, supalorvlew. Tbe middle ear (light blue) Is loC<Jt:ed v.ithln the petrous part of the temporal bone between the extef· nal ear (yellow) and innerear (green). The tympanic c.11llty of the middle ear cont.l!ns the chain of audltoryossldes. of which the mallws (hilmmer) and Incus (alllltl) are visible here. The tympanic avity communiatn anteriorly v.ith the pharynx via tne pharyngotymp;~nlc (auditory) tube. and It communlates posteriorly "With the milrtold air cells. lnfecUon.s can spread from the phyynx to the mastoid cells by tills route (Ke C).

AdltUi{tnlet)to - ---..,.;iMi-': 11li1Stokllllltrum

- - Faclaln.!M

Tensor tympani

Tendon cf Insertion ofst;pedlus

~-~~~~-SUpe

•...:...._.;"-'---

~

r-~~~~f--Tympank

plews

Exlltm1l - - audtoryanll

~--~~~~---Tympank n~

B Wills of the tymp11nlc c.tvlty Anterior view with tne anterior w.all remOIII!!d. Tbe tymp;~nic cavity is a slightly oblique space thirt ts bOCJnded by six walls:

• Lateral (membranous} wall: boundary with the external ear; f\:lrmed largely by the tympanic membrane. • Medial (labyrinthine) Willi: boundary with the Inner ear; f\:lrmed largely by the promontory, or the bony eminence. overiylng the bas;al wmafthecochle;~.

144

• lnfl!lfor (Jugular) wall: forms the floor of the tymp;~nlc cavity ilnd borders on the bulbafthejugularvein. • Postalor (mastoid) w.all: bonders on the air cells af tfle mastoid process. communlciUng wll:h the cells through the aditus (Inlet) of the mastoid antrum. • ~periar (tegmental) wall: forms tne roof of tne tymp;~nic cavity. • Anterior (caro1!d) w.all (removed here): Includes tfle opa1lng to the pharyngotymp;~nk (auditory) wbe and borders on the caroUd canal.

Hf!Gtl - - .9. Ear anti VestfbuiGr AppGI'tlbls

l'om!rior~l·

c:rwar c:;u~l

l'nlrncntory Postl!flcr Wllll of tymp.111lcGMty Mas«~lei ahdls Chord;~ tymp.111l

Fadalnerve

~pilnkGIV!ty. dlnk;llf,- lmpllltlntliiM'tomlc.Jinalattcnhlps Oblique s;~glttal section showing the medial w.~ll of the tympanic cavity (see B). The~natomlt.ll relationships afthe tymp;anlc c.Mty are p;arUc· ul;trly impomnt in tre~~ting cf,~ic suppurativt' atitis medi;l. During ttlis Inflammation of tile middle e.;~r, pathogenic bacteria may spread upw.rrd to ad)ilcern: regions. For ex.1mple, bicterfa may spread upward through the roof of the tymp;anlc cavity Into the middle Cl'ilnlal foss;~

C

lntl!mal

jugulmoeJn (lndtlng menlng!Us or a cerebral abscess. especially of the temporal lobe); they may lrwade the mastoid air cells (mi!toldltls) or slgrnold sinus (sinus thrombosis): they may p;ass through the ~lr cells af the petrous apex and enter the CSF sp;ace, causing abducent p;~ralysis, trigeminal nerve lnlt
lnt~la~~~

Pll;wyngatympanlc bl~ bony part s~ --~,...,.j~-:-4--.....:::~

meatul

Salp'ngopharyngeus D l'hlryngotympanlc: (audltllry) tiJbe

Medial view of the right half of the head. The pharyngotymp;anic rube (a lid!tory tube) creates ar1 open char1nel between the middle e
which, In tum, Is necess.ilry for normal hearing. The pharyngotympanlc rube is opened by the muscle.s of the soft p;alab! (tensorveli palatini arid levator Yell palatlnO andbythesalplngopharyngeus. which Is part ofthe superior pharyngeal muscle. Theft bel's of the tensor vel! p;alatlnl arfslng from the membr.anou~ lamina of the pharyngotymp.anlc tube ~re af special signific.lnoe: When the tensor lll!li pal;atini tenses ttle soft p;al;ate during swallowing, Its flbeB attached to the membranous lamina simultaneously open the pharyngotymp;anlc tube. The tube Is lined wtth cllrated respiratory epithelium whose cilia beat tDWllrd the pharynx. thus inhibiting ttle p;assage of microorganisms into the middle e.;~r. If this nonspecific protectllle mechanism falls, bacteria may mlgme up the tube and lnclb! a purulent middle e<~r Infection (see C).

145

Hftnl - - 9. Ear and Vestibular Apporatus

Middle Ear: Auditory Ossicles and Tympanic Cavity

9.4

Hml Artlalln surface for!nail

Nl'dc l..1tlnl p~

Hinde llllliii;i;~- Ovll -Mndaw

• .. L_

'Ji--a

Artfa.i•r

-+~

-s:

.....,...

_: 6 . . t!

f

~

_

Anll!rtor

1..

CNS

J 1.::)

Long

~ Llntlculir .,....,...

llgamtnt

Tympanic c..tty

Bcxtt

process

c

cna

mombron~

"',:a'~ ~~ Short \

•

wllh•nnullr st.pedlll

l)'lllponi:: --:=::;-=!!~..-

f»nmldal

errlnenoe Sbpeolha

nondon

- - (MI -Mnclclw

A

wtthannulr lllpedlil llgon~tnl

c

lnwdornallecl•r joint

IIIM!

B FuncHDnafthe_lal..rdlaln

CNI

I

l

CNS

J

Bal!

A Auditory oalda

The audlwry o551cles ofthe left ear. The 055lcular chain consists of tlu~e small bones In the middle ear(chaln function lsdesa1bed ln B).lt estalr lishes an articular connection from the tympaniC membrane \XI the oval window and consists of the folkMtng bones: • Malleus ("ham mel") • Incus ("anvil") • Stapes ("stirrup") Malleus: postafor view and anterior view c, ol lnCliS: mediiIv1ew 11nd antero~~Rral view e, f St.oprs: superior view and medial view Sl Medial view of the ossicular chain

1,b

NoR the arUcu~tlons between the malleus and Incus (lncudomalleofar joint)and between the incus and stapes (incudortapeclial joint).

146

Anterior view. a Sound WaveJ (periodic pnessure ftuc1l.loltlons In the air) set the tyrnJ»nlc membnne lniD Ylbmlon. The osslcu~r chillln tnnsmlts the vibrations of the tyrnpinic membnlne (and thus the sound w~) to the CMJI IW!dow, whldl ln 111m communlates them to an aqueous medium, the perilymph. While $0und-encounter wry little rtsi$tanc:e In air, they encounter considerably higher Impedance when they read! the ftuld lnterfaa! of the Inner ear (p1111ym ph). The sound waves must therefure be <~mplified ("impedance matching"). The dilference In 5Urface area between the tympanic membrane and CMJI window Incruses the sound preuun by a factDr of 17, and tills Is augmem:ed by the 1.3-fold mechanlclladwntage of the~ action of the ossicular dlaln. Thus, In passing from tile tympanic membnne to the Inner ear, the sound pressure is amplified by a factDr of 22. Ifthe ossicular chain falls to tr;msform the sound pressure ~ the tympinlc membrane and stapes base (footplilte), the pm1ent will experience conductive hearing lo" of magnitude appnllllimiltely 20 dB. b,c Sound WlM!S Impinging on the tympank membrane Induce rnotian in the ossicular chain, causing a tilting ~ent of the stapes (b normal position, c; tilted position). The movements of the Stipes base against the membrane of the oval window (stapedial membrane) induce c:orraponding- in the nuid column in the inner ear. ol The rTIO\IIements of the ossloJiar dlillln an essentially roclclng movements (the dashed line lndltites tile axis of the mCMITienb, the arrows lndltite their direction). TWo musdes affect the moblllty ofthe cmiadar chain: the tensor tympani and ltte stapedius (see C).

Hf!Gtl - - .9. Ear anti VestfbuiGr AppGI'tlbls

I'Qsl2rtor lgament rna~s

oflna.a;

SUpo211ar ligament oflncur..and supoer!orl19'1mentofmalleus

Annular rt;Jpedlal lljillll!nt Slllpedlal

membrane rncudort;lpt!cfaiJol'!t

--~~-7-----&~

Pyramidal eminence

......--==:J''::Oii:~~=-==-+--- ~p.wnlc

~~

IISII.n!

St)iOillilltold - -'-,:--''--Jrf lltfty

Facial nerve

- -:=----lf-'1 Chorda

tympani

c

OnlcUII' chain In tfle tymp1nlc cotty Lilter-..lviewafthe righte;~r. The joints andtheirmbilizing ligamenU can be seen. The two muscles of the middle Nr-the mpedlus and temor tympani-an ilso be Identified. The stopedius (lnneMted by the Stilpe· dlil branch of the fadal nerve) rnserts on the stapes. When It contracts, it stiffens the sound concl~~etion app;!ratus ind decn!
dlus reflextest) by measuring the challge In acoustk Impedance (I.e., the amplification of the sound waves). Contraction of the ~Silrl)lmponi(in­ nervilted by the trigeminal nerve via the medial pterygoid nerve) stiffens the tympanic membrane, Ulereby reducing the trin.smlsslon of sound. Boltl muscles undergo i reflex contraction In response to loud .iiCOUstlc stimuli. Nm: The chorda tympani, which contllru gumtory fibers for the ;rntl!rior two-thirds of the tongue, passes through Ule middle ear wllhout a bcny covering (mikillg it susceptible to injury during omlogic.ll surgery).

Tendon of Incus

Cha!W

tympani

Maleus

st.IJ)t!c!Us

Ex!!mll

teodao

l:enK!r l:yrl'9anl Mesol:yrl'9a num

&Jdtary

a !\a~

Tympanic membrl!M

H)'pc> l:yrl'9a num

Pharyngotyrl'9anlc

111be

D MIKDI
E arnk;llf,-lmportantl.,.lsofthetJmpankCOIIIIft,The tympanic Ci\llty Is divided Into three levels In relatlor1 to the tynnpanlc membrane: • The epitympanum (epitympanic recess, .iltl:lc) above the tympank membr.ane • The mesotympanum medial to the tympanic membrane • The hypotympanum (hypotympanlc recess) below the tympank membrane The epitympanum communicates -Mth Ule mastoid air cells. and the hypotympanum communleiltes with the pharyngotympanlc tllbe.

147

9.5

Lmral

semlctu!lar duct

Inner Ear, Overview

Antsfor Jemldrcular duct

Internal

Anll!rtor semi· drcularc;nal

acoustic me.m.tl

•

Sail

vesdbull

Ctxt!leu duct

A SchemaUcdl~gn~moftflelniM!t'Mr Tbeinnere.arisembeddedwithin thepl!l:rous p;artoftheternpar~l bone (see I) and conuins the auditory and 'llt$tibul;tr ~pp~ratus for healing and balance (seep. 1SO ff). It comprises a 171fmbrunous lobyrlnrh contained wfthlr1 ~similarly shaped bony/al1jdnth. The alllltory a,...ms conslru of the cochlear labyrinth With the membranous axhletlr duct. The membranous duct and its bony ~ell mab! up the codllea. which contalfiS the sensory epithelium of the audllnry 01pp;1ratu~ (OIYQn of Cora). The 'W!5tllullr apparatus Includes the 'Ye5tlbul;tr labyrinth With three semldrcular amo/s (sernlclillllar ducts), .a soccult_ and a ~ each of which a~ntaim sen$01)' epithelium. Whne each of the membra· noussemldrcularduc:tslsencasedlnltsownbonyshell{semlclrcularanal), the utrkleand sacaJie arecontarned In a common bony capsule. the ..ertibufe. The cavity of the bonylobyrinlh is filled with perilymph {IIM!Ym· phatkspoa~, beige), wflose comp!nltfon reflects Its being in ultnflltme of blood. The perllymphiltlc space Is coonected to the subilrachnold space by the cochlear aqueduct (• perilymphatic duct). It ends .at the posteriorsutfaa!ofthepetrouspartofthetzmporal bonebelowthein· tznnil
148

;-;:;;;;-:~:,:;:::;::~:::::::-:::=:!!!==:;_--.;;:::::::::..._

Clntllomeatll plane Llb!nl semicircular Ul'lll

Mastoid

Emmal

Pl'laSS

iOlultk mNtuJ

8 Pro)edkln oftfle Inner en onto the bonyslalll a SUperior lllew of the petrous part of the temporal bone. b Right lateral view of the squamous p.art of thetl!mpor~l bone. The ape11. of the cochlea Is directed anteriorly and later;rlly-not upward as one might lntultl~~ely expect. The bony semicircular a nils ane ortented at an approxlmiltely45" angle to the ardrnal body planes (corooal, traniM!rse_ ~nd sagittal). It is important to know this aiT.lngement when Interpreting thln·~llce CT SCilns of the petrws bone. Note: The location of the semicircular canals Is of dlnkal Importance In thernnil functiOn tests of the vestibular .app.aratus.. The lateral (horll.Ont;rQ semicircular an~l is directled 30' forward and upward (see b). If the head of the sup/lie pillientl~ ele\'ited by 30'. the horizontal semicircular canal will .assume a Yertltil allgnment. Since WiiiTn fluids tend to rlse.lr11giltlng the auditory anal Mth waJTn (44"C) or cool (30'C} water (relative tD the nornnil body tzmperature) an indi.ICe ~ thermal aJrrer~t in the endolymph of the semldrcular cam!. causing the piltlent to nnilnlfest vestibular ny3ugmus (Jerky eye movements, vestlbuJo.ocular reflex). Ilea use head movements .always stimulate both 'Ye5tibulilr apparatuse.s, caloric taling is theoolymethocl ofsi!J)Q'rote'ytesting tnef1Jnctlon of each vestlbul;tr app;1ratus Qmportant In the dlagno.!ls of unexplained vertigo).

Hf!Gtl - - .9. Ear anti VestfbuiGr AppGI'tlbls

Antl!ffor sem~

Anl:2flot

Vestbular

drrularduct

ampullarynen.oe

gangtol\ stJpefforpart

Vestibular aqutd.tct Vesti!KIIar

ganglon, lnfenorpart

,~~~~~~!;;~~-- Vesllbulod!odllmr -cochlear part ;::;....:...._....:..;.._-=:;;-@J~;.;;::.,__

SacxularneM

Po:sll!r!or senldr
duct

C lnrtervatfon ofthe membr;mous hbyrfnth Right ear, ~nteffor view. Affeftnt Impulses frcm the l'tCI!fl1Zir organs of the utricle, saccule, and semicircul~r c;~n;~ls (i.e., the vestlluillr ~P~ tus) are flm relayed by dendritic (perlpheraO processes to the two-part wstibular ganglion (superior ;md lnferlor parts), 'Which contains the all bodies (peribrya) or the afferent neu11:1ns (bipclar gangliorl cells). Their antral processes form the 'l'eStl'bulor port of the vestibukJC'Odl/ear tteM' through the lntenn;~l 01coustlc meitus and the artbellopontlne angle to the br.illn51Jem.

All'l!n!nt Impulses from the reaptor organs of the codllea (I.e•• the auditory •PPIU'IItlls) are ftrst transmlttl!d by dendritic (perlphmO proces5e$ to the spjrvl ganglia, which et~ntain ttle cell bodie-5 of the bipolar ganglion cells. They are loc.rted In the antral bony core of the cochlea (modlol115). Their central proce.sses form the cochlearpart ofthe vestibuklt'Odlkar-..

Note: also the section ofthefacial nerve ~hIts parasympathetic fibers (nerws Intermedius) ~thin the lntenn;~l iudltory Cinil (see D).

D Passage of cnnllll rterws through the rfght lntemalaCOUitlc:

mema Postaforobllque vlewoflhefundus of the lmnn;~l acoustic meatus. The ipproxlmately 1-cm-long lntemil auditory Cinil begins it the Internal .ilcoustlc meatus on the pcstefforw.illl of the petrous bone. Itcontains: • the vestlbulocodtlear nerve witt! Its codllear and vestlbular parts, • the marlaedly thinner fad~! nerve With Its parasympathetic fibers (nervus intermedius). and • the labyrinthine artefy and vetn (not shown). Given the close proldmltyofthe Yestlbulocochlear nerve and facial nerve In the bony Cinal. a tumor of the Yestlbulocodllear nerve (acoustk neu· roma)mayexl!rtpressureonther.ilclalnerve,leadtngtopertpheralf.adal paralysis (see alsop. 79). Aalustic neun:~ma is a benign rumor that origInates from the Scflw.lnn cells of venlbular flben. and so It would be more acauite to eilllt a I'I!Stlbular sdlwonnoma (see alsop. 82}. Tumor growth always begins In the Internal auditory Cinil; as the tumor enl;nves it may grqw into ttle cerebellopontine angle. Acute. unilateral inner e
._

SxalloUtrlalo· ~or ampLllaryneM .ilmpullaryNrYe ampularyneNt'

149

Hettd - - 9. &r Gnd Vestibular Apptlrabls

Ear: Auditory Apparatus

9.6

Sa!;a vrst~bull

Vesl!bl.far (Relssner)

membrane

Fxtal nenoo

SpiraIIi~ --Chard;~

tymp.llll

Bony

01111ndCGr!l

spiral l;mb;a

ll&'lllr b

membn~ne

•

A loc:.1Uon 01nd struc:ture of tfle cochlea

a Cro.ss-se
troU$ bone. b The tillft a~CT~partmenl$ of the cochle<~ranal.c Cod!leartumwlthsa'ISOryapp;lritus. The bony canal of the cochlea (splr.al anal) Is ~ppraximately 30-35 mm long in the adult. It makes 2 ~ turns around Its bony iXls. the modtolus, ~Mllch Is permeated by branched Q/11ities and contains the spiral ganglion (peri· k
150

c

steadily from the base of the codllea to the apex. High frequendes (up to 20,000 Hz) are percel'~ by the narrcw portions ofthe basilar membr.ane ~Mlile low frequencies (dQWTI to about 200 Hz) are perceived by Its broader portions (tonotoplc otyantzob'on). The basilar membrane and bony splr.ill lamina thus form tile floor of the cochlear duct. upon which the actual organ of hearfng, the organ of Corti, Is loc.rtl!d. This organ consists of a system ohensory cells and supportlr~g ails CCMI'I!d by an acl!llul~r gelatino~JJ ll;!p, the tmorial mem~. The sensory «
tr.lnsfonn mechar~lcal energy lr1to electrochemical potentials (see below). A magnified crosHectlonal view of .a cochlear tum (c) also reveals tile st1'ia ~~~~KUiotis, a layer of vascula~ lzed epithelium lr1 which tfle endolymph b formed. This endolymph fills the membr;noU$ labyrinth (.appeo.arlng here .as the cochlear duct, which is part of the labyrinth). The organ of Corti Is loc<1ted on tile basilar membr;ne. It tr.lnsfonnstheenergyoftheacoU$tlctnvellng wzve Into electrical lmpulse.s, which ane ther1 carried to the br.ain by the cochlear nerve. The prfriCip;ll «
Head - - 9. Ear and Vestibular Apparatus

-

T~g

RDund

wlndaw llatllar membrane ' - - ---=-:::.;,.=--

--l'Jmp;lnlc

merrbrine

a 5olnd aJncludlon clu.... hurTng • Sound a~ncluct!CIII hvm the mlclclle Rr to the Inner Mr. Sound wnes In the air deflect the tymp;~nlc membrane, whose vlbr.ltlons are cond uctBd by the ossicular chain tD the owol window. The sound preHure Induces motion of the CMII window membrane. whose vibrations are, In turn, nnsmlu.d through the pllflymph to the bilsllar membrane cf tile inner ear (seeIt). The round window equalizes presllures between the middle and Inner ear.

Inner

ShNrlnglllf the stl!reodll

t..lroells

•

Alfor81t~-· nerwftbers

b Fclr1Mikln cf • trne.,g w.n In thol codllu: The sound wave begins at the oval window and travels up the sala ~stibuli tD the apex of the cochlea ("trndlng Wille"). The amplitude of the travelIng wave gradually Increases as a function of the sound frequency and reaches 01 mildmum Y111ue at particuIn sites (shown greatly exaggerated In tile drawing). These arethe sites where the rec.eptDrs of the organ of Corti are stimul&d and signal transduction OCCUI'$. To undersund this proceu, one must first grupthe structure ofthe organ of Corti (the actual organ of hearing), which Is depleted In c.

Outer

a..n.,

1-.lre~lll

membr.lne

C Orpn ufCartlat ret (1) 1nd ddedecllly1 tnwllng- (b) The ~ling...,~ is gener&d by vibrations of the CJY~I window rnembr~ne (see lb). At each site thlt Is assodlted with a particulu sound

frequency, the tnvellngWIW! causes a miXImum deflection of the biiiSilar membr~ne and thw qf the tectorial membrane, setting up ,hearIng m~enb between the two membranes. These shearing move-

ments cause the stereodl Ill on the outer hair cells tD bend. In response, the hair cells ;octi,_,ly change their length, thereby incmlling the local amplitude of the tra~~ellng Wille. This .cldiUonally bends the stereodl Ill of the IIIMrhalr cells, stlmulltlng the rele.lse cf glutamate ~t their !Ysil pole. The release <#this subst.-.nce genema an exdutory potential on the .;rlh!rent nerw flbers, which Is tr01nsmlttled to the br1ln.

151

Hettd - - 9. &r Gnd Vestibular Apptlrabls

9.7

Inner Ear: Vestibular Apparatus

Ampultlry~

A Stl\ldure of the vestWw •pp~ratu•

wltlunllerlor

ampullarylll!rw

Thevestlbularappar.ttuslslt1eorganofbalan~.

It consists of the membranous semldrcular duru, wflich contain sensory ridgel (ampul· lary crests) In their dilated portions (~mpul· lae). and of the saccule ;md u!Jfcle with !heir macular organs (their location In the petrous bcAeisshown inB,p.148). The sensory organs In the semldrcul~r duru respond to ~ngular aa:eleratlon while the mKular organs. which have an appi'OlClmil1lely vertical and horrmntal orient;~tion, respond to horizontal (utricular macula) and vertical (saccular macula) linear aa:eleratlon, as well as to gr.Mtadonal forces.

~~m~--~~~--j

Vts1lbullr

!jiiM~IOI\ 7~ •

5Ul'C'riOri)Oirt

crcuarduct

•-:-::-- - - Vt$1lbullr !jiiM~IOI\

lnfl!rlorput

~o~Ural

-----,,..:;...-

sernldrOJiardiJCl

I Stl\ldureofthn~J1NIInnd
Cross-section through the ampulla of a semi· circular canal. E
C Stl\ldure of tile ut.rtcul;n md jlllcaJIIr maa~lle The maculae are lt1idaened oval arus in the

epithelial lining of the utrlde and sacaJie. each averaging 2 mm In diameter and containing arr;rys of sensory and supporUng cells. Uke the sensory cells of the ampcJIIary ctest. the sen· sory cells of the macular organs bear spedal· lzed stereocilia. which project Into an otolllt11c membrane. The latter consists of a gelatinous layer. similar m !he cupula. but It has caldum carbonil!le crystals or otoliths (swto/tths) an· bedded In Its surface. With their high spedflc gr.Mty, theseaystalsexerttracUonontheg~ latina~D mass in response m linear accelera· tfon, and this Induces shearing movements of the cilia. The sensory cells are either depolar· lzed or hyperpolarized by the movement, d~ pending on lt1e a(oentation of lt1e cilia. There are two distinct categorln of vestibular hair cells (type I and type II}: type I cdls (light red} are goldet shaped.

152

Enclalymphltlc diJCl

Ampulllryccet witt! pomrlor ampularyn~

Senldm~lll'

anal

-~--CIIaof

seruoryalls

,....--;;,..-- Supportilgcl!ll ,...._......,.;:.-- Str!S«Y cl!ll

Hf!Gtl - - .9. Ear anti VestfbuiGr Apptuorus

--

- -

Stereodlla

SI!O!Ory all

1111111111111

nrne

l

111111111111111111

AfferentneMflbet

E Spcdlllzed orlentltlonnf tfu: stereocllllln the vatllul.. 01pp;m1tus (ilmpllll;uy crest met lniiCIIIn) Because tile stimulatiOn of the sensory cells by deflection ofthe stl!reo· cili
D Stlmulustnnsductfon lnthevestW81'ten•orycelh Each of the sensory cells of the maoulae and ampullary crest bears on Its apical surf.lce one long klnoclf!um and appi'QldmatJ!Iy 80 srereoclf!a of gr.iduatl!d IC!Ilgths, fanning an array thilt resembles a pipe organ. This arrangennent results in a polar differentiation of the sensory cells. The cilia are straight wfllle In a resting state. When the sti!reodlfa are deflected toward the klnodllum, the sensory cell depolartzes and the frequency of .ictlon pot4!111:1als (d!schilrge rare of Impulses) Is Increased (right side of di
lnten~ctfon of contnlmn~l semlclnd..Cinllls during hNd rotation WhC!Il the head rotat2s to tile rfght (red arrow), the endolymph flows to the left because of in inertial mass (solid blue ai"!''7N, taking the head as the reference point). <Ming to the alfgnmC!Ilt of the stl!reodlfa, the left and right semlcfrcular canals are stlmulat2d In opposlre fashion. On the rfght slde, Ule srereocllla 01re deflecttd IZIINard the lclnocll!um (dotted ~rrvw; the discharge rate increases). On the left side. the rterecoli~ are deflected away frvm the klnocllfum (dotted arrow; the dlsdlarge rare decreases). This arrangement heightens the sensitivity to stimuli by lncre.islng the Jtlmulus amtriiSt between the two sides. In cUter \Wilds, the difli:!rence between the decreased firing rate on one side and the Increased firing rate on the other side enhances the perception of the ldnetfc stimulus.

F

153

9.8

Ear: Blood Supply

A Origin of tile prlndjUil •rtettes of tile

tymp;mk c.mty Elapt for Ute caroticotympanic .;utel'fes, which ~rise from the petrous p.art of the inb!t· nal ~rotld artery, all of the vessels that supply blood to the tymp.anlc C3111ty arise from Ute external carotid al1lery. The vessels have many an;artomoses with one another and n!ach the aud!Wry osslcles. for example, through folds of mucosa. The osslcles are also tr;rvened by Intra osseous vessels.

Artely

o.tgln

Dlstrlllllllan

carot~cotympanlc

lnbemal carotsd a1121'y

Phal)l'gQtympanlc (audtory)blbe .and an!l!rlo rw.~ll oftil~ l.yn'9;l nlc avlt.y

Stylomi!Jtllid ..ury

Port«lor atriwlir <~mt)'

Pomrior 'Mil of thoe tymp;Jnlc avtty. mastllld alrcdls. sUpectus muscle. stipes

lnferlortymp;Jnlc arts)'

Asandng pharyngal lmty

Floorolthoet.yn'9;1nlcavlt.y. promontory

Deepaurrcularartsy

M;lll111aryal'tlery

~panic ~mbr;~ne. ftoorofthetympanlc

Postllrior tympanic

Stylomastoid lrts)'

artl!!fes

c;Mty

<Jmty

Chordil tympani. tympanic membnii'Ae. llliiiiNS

SUperfortympanlc:.artery

Middle meningeal artery

Tensor tympani, roofofthetymp;Jnlc c;Mty. sbpeS

AntA!rior tympa nlc <~mt)'

M;lll111aryal'tlery

T~panlc ~mbr.me,llliiSidd antrum,

malleus, Incus

Sub<Jrcum>amey

Asaendtlg branch cJ supeildiJI petmal am.y

~~~i-

Desa!nd:ng lnnch cf supeilclll Pttn~AI~rtlery

Anllrfor Criii"OII.artltry

Bnnch~to

mpedlus (mpedal bn~nch)

Tensor tympani Stylom<JStllid ----'<...,-<JI'tlery

.....::,.Jfl

Ma.stald lll12l'y

Pomrfar

l.yn'9;l nlc b r.!n ch

DeEp au r'lc:Ua r

tlferfa r l:)mpa nlc

al'tlery

lll12l'y

B Artertes aftfle tympanlt e.wtty and maltOid air celt

Right petrous bone. antetfor view. The malleus. Incus. portions of the chorda tympani. ;rnd the ;rntafortympanlc artay have been removed.

154

Tubal artsy

Hf!Gtl - - .9. Ear anti VestfbuiGr AppGI'tlbls

._.......-~;,----- Mastoid
Tms« tympani Anterior - -::oooi;gll'

~~h=:-':>"'-'':--

Stapedloll br.lndl lncu~laljont

tym))llllt lr'b!
(stapes n!rna.ed) ~~~~..r:.--'',1:!~..,:=-...:t...s..

Chardatympanl

__ PosiB!or l.yn'9anlcartl!ly

c

Vaw~rsupplyofthe ouiCIJIII'dlaln and tympanic membrane

Medi;dYiewofthe right cymp~nic membrane. This ~ion neaives most of Its blood supply from the anterior tymp;rnlc artery. With lnflam-

miltlon oftile tympanic membrane, the artertes may become so dilated tmt their course in the tympanic membrane can be seen, as illustrated here. Ve'Jilbularrwrve

U1·~~-----~---N~

lntennedlw;

-T--------- Cod!learl'lli'Ve ~~~~---::----:~---Common

cochiNrarttry

\\-- - - - Cod!leir

artery proper

D Blood supply of die llibyrfnth

Rlghtanrertonlew. The labyrinth receives all of Its arterial blood supply from the lnrernal audllxlry artery, a branch of the anterior Inferior tef· ebeUar artery. The labyrinthine artery occasionally arises directly from the b;Jsilar ;artery.

155

10.1

Coronal Sections. Anterior Orbital Margin and Retrobulbar Space

~~----~~--~----~--~~

plm

E~d----~r-~------~~~~

ails Mlddlenml ------l--.----"'-==c1=--------'-· merlus l~ltll---r:.......,;,;.:........:....,,...,.=.. lleM!

.......:..:....:;,.:..:..- -......::,....--- Antuppermolar

-----+ --- Bucxfrllllor

flnt~molar

~~~----~~~~~ ~~----~~~~~-/

Plirtysma ----->...;;~~;;;;;;;::;;:;:_

A Coronal sec:Uon through 1M anterklr orbltlll margln Anterior view. This seclicm of the skull call be roughly subdivided into four regloru: the oral cavity, the nanl cavity ~nd sinus, the orbit, ~nd the ~nll!rior cr~nlal fossa. Inspecting the region 1r1 ~nd around the onel c.wtty, we observe the muscles of the or~l floor, the apex of the tDngue, the neurov.asrular structures In the mandibular e<~r~al. ~nd the first molar. The hand palm separ.ttes the orill c.;Mtyfrom the nasal GMty. whkh Is divided Into left and rtght hallles by the nasal septum. The 1r1ti!rfor.ilnd middle nasal conchae c.an be identified along with the latJ!ral!y situated maxillary sillus. The structure bulging down Into the roof of the slr~us Is the lnfraorblt.ll e<~nal, which tt.ilnsmlts the frlfrilorblt~l nerve (branch of the maxillary dl·

156

b.r-- ----:,....--- lnfl!rlor alwl!olu ni!I'Vl', ull!ry, and win In 111indbuluc.an11

.......,..........,..=----- D~c

~~

(anterior belly)

\llslon of the tlfgemlr~al nente. CN V:J. The plar~e of secUon Is so far .ilnteriarthat it daes not cut the later~! bony walls of the orbits because of the later~! curvature of the skull. The section p;~sses through the tr.ln5p;~rent vltrea~JS body. and three of the six extr.locular muscles can be Identified In the retto-orbltal f.tt. 1\No .additional muscles can be seen In the next deeper plane of section (B). The spa a! between the two orbits Is occupied by the ethmoid cells. Note: The bony orbit~ I plare Is wsy thlr1 (lamina papyrilcei) and mil)l be penetr.ated by Infection, tr.auma, .ilnd neopl.asms. Ill the anterlar aa1lll faaa, the section passes throtJgh both frontal lobes of the brain lr1the most arlll!rior portions of the cerebral gray matter. Very little white matter Is visible at this level.

....-:=~1ll'""'=:--::-:--...-__;'-:--=-:,,....-----

Suptrfor sag'lttllstnus

Frontlllobe ---f-~~~------

ofaerebrum

EIM!old

Cl!lls

~--==-=---:--'':--':"'=:..,........:..-;':-::--:---:---

MaxlhiYslnw;

Middle

nasalc:oncha

--+-:.......:...,...,.,.,~-----,-7---

M-. ---- '.: .,.-M-.

~uperfklal

part

dfleppart

---'<----~")

~-.-+--- tlftrlor lllwolarnel'lle. al18y.

andwfn In mandlbullrc:.w~l

~~~----~~~~~~~--~ ~~--~--~~~~

~,..:---------,'--------

Olg;U1c

(anb!rlor bdly)

B Coronal ~on through the retrobUwtpace Anterior vii!W. Here, the l»ngue is a.rt: at a man! posterior lew!l than in

A and tflerefoAa appears broilder. In addition to the oral floor muscles. weseetilemusdesofmastlcatlonor~thesldesofthestull.lntheorfllt
eldraocularmuscles. andtheoptfc nen'l!. Theorbltcommunlt:.ltl!llate!'allywith the infratemporal fo$S~through the inferiororilital fissure. This section a.rt:s through both olfactwy bulbs In the anwrior aanlal fossa. ;md !he superior s;sgltt
reglofl we can Identify tile retrobulb.lr space Mth ItS fatty tissue. the

157

10.2 Coronal Sections. Orbital Apex and Pituitary

Fl1llltlllobe

----f~r'----:-:7---=----:--­

Olt.n:tory nerve

ola!n!brum

SUperior oblique

v:::;;,......- +-- - Inferior lllwdarnerw.. artery, .and Win

~~~~----7----D~mk

(antsforbdy)

A Coronal sec:Uon ttl rough 1M orflftal•pu: Anterior view. The soft palm! replaCB the hard palate in this plar\1! of section. and the niiSal septum becomu osseous at thiJ levd. The buce<~l fat pad Is
158

are sunken In patients 'With encktage e<~ncer. This coronal section Is slightly angled, producing an apparent discontinuity in the mandibular

ramus on the left sldeoftheflgure (compare with the continuous r.rmus on the right side).

•~=----;::-=---+.'-:--?..,..,--'=,.--------

Superfor !l
l"<
Had of audile nudeur.

ln11emal upsll~ 1\ltamen

OpllcneM! Ml!erior

Oculomotor

O!febralarmy

I'M!Me

htemll arotkla"t!ry Tempcrallobe

~

fl!tultlry

Trcchl.s~rneM!

-Abduamn~

Ophth;llmlc dMskln (011 V,)

Crwmous slnw;

Nasopharynx

B Coronal ~on through the pituitary Anb!fiDI' view. The nasopharynx. oropharynx. and laryngopharynx Cln now be Identified. This section cuts the epiglottis. bEiowwfllch Is tfle su·

praglottlcspace. The plane cuts the mandibular ramus on both sldes. and a relatively long segment of the mandibular dMslon (CN v~ an be Identified on the left side. The paired sphenoid sin1.11es al'l! visible, separ.rtl!d by a median septum. Abcwe the roof of the sphenoid sinuses Is the pi· tult.1ry (hypophysis), which lies In the hypophyseal fossa. In ttre cranial cavity, the plane of section passes through the middle cranial fossa. Due

to the preSI!OCe of the carotid siphon (a 180' bend 1r1 tfle CM!mous part of the internal carotid artery), the section cuts the internal carotid artery twice or1 each side. Cranial nerves can be_, passing through the cavernous sinus or1 ttrelr Wilt'f from the middle cranial fossa to the orbit. The sup«tor sagittal sinus appears In cross-section atttre attachment of the falxarebti. Attllelevel ofthearebrum, the plane of section passu through the parietal and temporal lobes. Intracerebral structures appearing In this sectfon lr~elude tfle caudate nudeus, the putamen, tile Internal capsule, and the antenor ham of each lateral ventrlde.

159

10.3 Transverse Sections. Orbits and Optic Nerve

~--~~~~~~~--~~~---­

nucleus

~~~----~~--~~~~--~--~~---J IQUeduct

Cholllld

----~~--=---......:;.----":!

pll!lWS

A lh!nnret"Sesectlontflroughthe uppl!t'leveloftfleorbb Superior lllew. The hlghe.st section In this series displays the muscles rn the upper IM!I ofthe arbit (the crbitaiii!VI!Is ane described on p. 13611). The section cuts the bony crlst<1 gall! In the anterior cr;~nlalfossa, flanked on each side by cells of the ethmoid sin liS. The sections ofthe optic dll· asm .and adjacent optic tJact are parts of the drenCI!phalon, which sur-

160

rounds the third vartrlde at the centl!t' of the sed:lon. The red nudws and substantia nigra are lllslble In !he mesencephalon. The pyramidal tract descends in the Cl!t'ebtal peduncles. The section pass!!$ through the posterior (ocdplt
lllt8nill «Jrotid .mry

Tempor.~lts

l'llultuy

Oc:ubmator nente

Cavemous $11\US

)

B.DIIiraM')> lnll!!l)edunculllr foss.l

Pons

~lar---~.---~---~~-~~~--­

vetmls

- --+-:,;:=-,=-'::o:-=-::=-od- - -

8 lhlnswne section tflroush Ute optk: nll!f'ft md pttgt.Jry Supertor vrew. The optic nerve Is seen Just before Its entry 1111» the optic c.;mal, indicating that the plane of section passes thnoLJgh the middle level of the orbit. Bee<~ll!e the nave completely fills the e<~Bal. growth dlsturb;mces of the bone at tills level may a use pressure Injury to the ntM!.. This plane cuts tfleocularlensesand theulls
l.lrtmlventr!d~.

oalpll
Ifnth. The Internal carotid artery an be Identified In the middle cranial foS;Sa, embedded In the cavernous sinus. The sec!Iori cuts the oculomotor ni!NI! on either side, which cnune.s in the lateral wall of the cavernous sinus. The pons and cerdlellarvermlsare also seen. Thef.rlxcerebrl ind tentorium cerebelll ippear iS thin lines that come together it the straight slnll!.

161

10.4 Transverse Sections. Sphenoid Sinus and Middle Nasal Concha

Vome< (bony part

ofnnalsepC!Jm)

~--~~~~~~~------~-----~d

sinus

Internal - - - T -.......~:-:'F----:--:-=:~~~ca«!d artery

Temporal bane,

-~4:-----:~::-----:-:~7---~="""

pe1rat.5 p;ut

11fge
·--------r-----':':-:-~'-i-i--- Tent(lrt~

~~~:belli

Sll'alght

slnt.5

Superior

--~==~~~~:.......;.---,-....,

sag'lttlhlnus

A lh!nnret"Se section til rough the sphenoklstnus Superlorlllew. This section arts the Infratemporal fossa on the later.ill aspect of the slwll and tne temporalis muscle that lies within it. The plane passes th(1)1Jgh tne lower level of tne orbit. and a small portion of tne eyebilllsWibleontheleftslde. Theorbltlscont:lnuousposterlortywlth the Inferior orblt.ill flSSIJre. This section dlspl.ii}'S the .ilntenor extension

162

of the two greater wings oftile sphenoid bone and the posterior extension of the two •petrous bones• {petrous parts of the llempor<~l bones}, which mark the boundary betwel!!n the middle and postl!riorcranial IMsae (see p.12f). The clivus fs part of the postenor aanlal fossa and lies In cont.ilct with Ute basilar artery. The pontine ortgln ofUte trigeminal nerYe .ilnd Its lnlraaanfal course are cle..rly demonstrated.

Fao:lalneM

s~

- ---->;;=f"---=-.:....,:.-:=::---=..:=-----'

saglttlhtnus

8 lhmswne sec:tlon ttnoush the middle n.JNI concha Supertor VIew. This section below the orbit passes through the rntraorbitalneM! in the accordiri!Jiy named nnal. Medial to the infra~:~rbital nerve Is the roof of the mil:ldllaryslnus. The zygomatic armis VIsible In Its entfrety, ;md portions of the mil!des of mastication medial to the zygomatic arch (masseter, ternporalls, and lateral pterygoid) can be seen. The plane of sectitln passes through the upper part of the head of the mandible. The mandibular division (CN VJ) appears In aoss-sec-

tton In Its bony canal, !he foramen ovate. It Is eY!dent that the body of the sphenoid bone forms the bony center af the base of the skull. The fac~l nerve and venibulc;~cochlear nerve emerge from the brainmm. The deMate nucleus lies ~thin the white matter of the cerebellum. The space around !he ant:ertor part of !he cerebellum, the pontoce~ lar dmrn, Is filled ~th cerebrospinal fluid 1r1 the lllllri!J rndMdual. The tranJI/efW sinus is prominent arnQrlg the dural sinll!n oftne brain.

163

10.5 Transverse Sections. Nasopharynx and Median Atlantoaxial joint

~,_.,:;;::::;'---

E'xtl!nwl auditory anal

Glossophatyn-

gmlnerw lnumal

Jugular win

....~~-__:_--=-:--:!---- TranMne sinus

A lh!nnret"Se section through the n;noph;~rynx Superior view. Tills section passes through the external nose and par· tions of the cartilaginous nasal sk21etcn. The nasal cavities communi· catewlth the nasopharynx through the choanae. C
164

Notl! the Internal Jugular vein and vagus 11erve, wltlch piSS through the carotid sheath In company with the Internal arotld artery. A numbef- of cranial neNt.S that emerge frDm the skull b.ise are dis-

played In crou·sectlon, such as the facial nerve coul'llngln the fudal canal. Tills section 01lso cuts the iurkle irld portions of the extanaliudltorycanal.

Ocxlpltll bone

Splrllll cord

8 lhmswne sec:tlon ttnoushtne ml!dl~n ;atlant.oalal jatnt Supertor VIew. The section .ilt this level p;asses through the connect!~ tissue sheet that stn!b:hes 01/l!!r the bcr~e of the hard p.1late. P«ti~:~ns af the upper ph;lryngeal musdes are sectioned dose to thEir origin. The neurov.ncular stnuctures In the carotid she.ilth are also well displayed. The dens of the axis articulates 1r1 the medlar~.iltfantciiX!al jornt-w!th the

f.rcet for the dens or1 the posterior surface afthe anterior arch of the atlas. The trafiSYerse ligament of the atlas that helps to stabilize this joint can also be identified. The wrtebral artery and its aaomp.anyir~g Vl!ins

are displayed In crws-sectlon, as Is the spinal cord. In the occipital region. the section p.1sses through the upper portion af the posterior nedc muscles.

165

Hftld -

JO. ScdfonaiAnatomyo(tMHnd

10.6 Midsagittal Section, Nasal Septum and Medial Orbital Wall

~b~----~~--~----------~~-;

Sphonold slnUJ

_____________.,:-_

-~;:...;...--=:;__.:;;:...

Olvus

I Nu...,tum _ _:::.-- - - - - -

Hinl~

polm

Nuduillgalllllll

Soft p;lm

l.alyngul arUiage

A Mlclsqlttill secdon dlro..h dlen&Sill septum Left la~l vi-.The midline structuteS ~re parlicubriywell displayed in

thb plane of section. ;md the an~tomlcal structures at thl5 1~1 can be roughly ilsslgned to the flldllllbletan or neui"CXJ'anlum (crilnlal Vi ult). The IOWQt1-1 of the facial skeleton is formed by the oral floor muscles between the hyoid bone and mandible and the overlying skin. This section ilso puses through theeplgle!Uis ilnd the larynx below 1t.which are considered p;~rtGfthe mvicalvisC2ril. Thehird and softp;~latewtththe uvula define the boundary between the om md nasal avltles. Pclstelfor to the uvulio b the oropharynx. The section ind udes the ""sal septum,

166

EplglaWs

which diYtdes the nilsal avtty Into two cavities (SKtfoned ilbow! and In front of the septum) that (Ommunicate with the n;asopharynx through the choanae. Posterior to the frontal sinus Is the anterior aanl;ll fossa, which Is part ofthe nlllrocl'llniUn. This section p;~s.ses through the medial surface of the br<~in (the falx cerebri has been remllllled). The rut edge of the corpus allosum, the o~Rdory bulb. and the pituitary are also shlMil. Mn the median atliontDulil }clint (whose stability must be evalwated ilftertnluma to the cerflal spine).

Medlll>egment of gobus polld&a

Unwo

UllinI

v.:ntrtcle ~or

-

11\illmlc nuclei

a rebelar

drl2m

-brol orlil!ry

lnforlor -...,.J :..__..:._;..;~...,......___,

,;_---

~ -apllls

~

nucundl•

·

Plldnepr1XIISJ, - - - : - - - - - - - - . . . pa~eiUicus

~ormlnar

- - - - Sen'lsplnols ~$

@?~ , ~--

Maiii----

Olal ~

=~ C3'1'1nalneNO Spl.,.,ba!Mds

Sections of wrt.bralorlil!ry

8 SagtltiiiiKIIon lhraut~h the melllil orbfblwall Leftla~l vi-.This section paues th.-ough the infef111r and middle n:~­ sal COI1CNe within the NAI ciVIty. Above the middle ni!Sal concha are the ethmoid cells. The only parts of the nasoph;uynxvlslble In this section ;rea sm..rl lumin;l"-ee and the lateral wall. whidl burs • secticm

C5 spinal C6 spnal C7 splnalnerw ,..,..

ni!NI!

of the cartilaginous portion of the pharyngothymp~nlc tube. The sphe-

noid sinus is also displayed. In the region of the cervial5pine, the section cuts the vertebral artery at multiple levels. The lateral sites where the spinal nerves emerge from the lnt«wrtl!bral forimln:~ ire ciNrly displayecl.

167

Hftnl -

10.7

JO. ScdfonaiAnatomyo(tMHnd

Sagittal Sections, Inner Third and Center of the Orbit

Phiryngotymponlc (ludlb,.y) tube l'orb!rlor menlngula!Ury
a«tiSSOY ni!IW

-

Hypaglaual

-~.....,-~~:::;~~~~~r--::"--- llll!t~laootlil..uty e.,;;o:::......,..!'..;,;~-....,:...---

Obllquus

c.pltls lnfwior

Inferior pharyngool cons111c11lr

A Saglltill sedlan ltnVU~h the INter tHrd ofthe orbit Left lateral view. This section JNS.Ses through the m.uillary and frontal 'lnuses while displaying one ethmoid cell ;md the perlphen~l part ofthe sphenoid sinus. It passes through the med~l portion of the Internal carotid ~rtt'ry and submandibulir gland. The pharyngeel and lllilltiutory muscleure grouped aboutlhe artlllglnous JNrtofthe pharyngotym-

168

panic tl.lbe. The eye~Nil and optic nerw are cut perlphera lly by the section, which displays relatiwly long segments ofthe superior and inferior rectus musdes. Sectioned brain structures Include the external and Internal apsules and the lnterwnlng put.am111. The amygdala and hlppoCi mpus c.an be idt"ntilied near tht' bise of ttl«' brclin. Asection of the trigemini! ganglion ippears below the arebrum.

- - - - - - Semlsplnolll Oplll$

.~~~~~~----~~~----~----~o~~a. ~~~40:/.F-----~--- Obfqws

a piiS Inferior .·.:.~L-------SplenlusCII!rvlds

Splenius c;opltli

Body ofrNndble

Comman

carotid .tory

8 SagtltiiiiKIIon lhraut~h the ~ppi'Qidlnlte cenbr of the orbit Left lab~l view. Due tD the obliquity of this sedion, the domin:~nt stnJcture In the oral floor region Is the mindlble while the oral vestibule

.JppNrs .1s a narrow slit. The buccal and miiStl~ry muscles .1re proml· nently dis~ in this plane. Much of the orbit is occupied bythll! 11!\'11!' ball. whlm.Jppe.Jrs In longitudinal section. Aside from a few sections of

the extraOOJiilr musdes, the orbit In this plane Is filled with fltty tissue. Both the intern:!I carotid artery and the intllmal jugular vein are demon· str<~ted. Except for the foot ofthe hippocampus, the onlyvlslble cerebriil structures .111! the whlt2 I!Ytter ;md mrta. The fad.JI nerve and vestI· bulocuchlt~~r nervi!! an bll! idll!ntifled in thll! intllrnal auditory canal.

169

Neuroanatomy Introduction to Neuroanatomy . . . ........ .... ... 172 2

Meninges of the Brain and Spinal Cord ••••••• •• .. 186

3

Ventricular System and Cerebrospinal Fluid •••••.• 192

4

Telencephalon (Cerebrum) .... ....... ...... .... 198

5

Diencephalon .••••••......•••• •......• •••••••• 210

6

Bralnstem ... .......... .. .. ............. ...... 226

7

Cerebellum . • . ••••.... .. ..• •••••.....• ••••• .. . 238

8

Blood Vessels of the Brain .... ..... . ..... . ..... .. 246

9

Spinal Cord ....... ............... .... .... ...... 266

10

Sectional Anatomy of the Brain ......... ......... 292

11

AutonomlcNeiVousSystem ...... .. .... ........ 316

12

Functional Systems ................... ......... 326

1.1

Central Nervous System (CNS)

• A Cent:r.ll ne,_. systiem,ln sllu 01nd In lsol;rt:fon nervo~JS system In situ, left lmr<~l view. b lsolmd centr<~l n~systl!m. anterior view. The nerwus system Is concerned with the pemp1!on of processes that ll!ke plilce Inside (enteroceptlon) or oublde the body {exteroceptlon) and with Internal .and external communlutlon. ca~n the dlwrslty of these intem!latl!d tasks, the body is endowed with a compla nerwus system !hilt can be subdivided In various w.ays. One bilslc pr!ndple of di~lllc.ttlon Is to divide the nei'\IOus system morphologically Into <1 pe· rlpherill n~ system (PNS) and <1 central nervous system (C..S). The antral nervous systl!m wnsists of the br~in ~nd spinal ccwd, which are seamlessly lntertonnecte
a Central

172

b

rlpheryofthe body. Macroscoplcilly,lhe briln and splnill cord consist of graymilttef.andwhltem.ttter(seeB). Tbesurfaceofthebralnlsgraybecause of the presence of nerve all bodies. The surface oflfle spinal wm Is white beciuse of the presence of nave all processes (alUlns) and thelrlnsulat1ng myelin sheaths(= axons. see C). The CNS communlc.ttes Mth the rest of the body ttl rough the cr<mlal nerves .and spinal ne!Ve.S, whose siWofemef!!enaareshown in b. To shield tbeCNS from~ nallnjury, the bratn and spinal cord are mea Jed by bone (aanlal bones and ~rtebrae). Situated between the bones and CNS are the ~rings (meninges) or the brain and spinal cord, which are the flrtt structures encounten!d when lfle overtying bone is 1'1!!~. Having already desalbed the bony anatomy In an eariler chi~r. we now proceed to a desalptfon ofthebr<~ln and spinal co~.

• B Dlstl'lluUartotgrayandwhltl! mattl!t'lndM!CNS

a Coronal sectior\ through the arellnJm (telenaphalon, seep. 198 If). b Cross-section tilrough the spinal cord. Even Ofl gross Inspection, sections of tile briln and spinal cord differ marktdly In tilelr appeal'ilnce due to dlffen!nces In tile distribution of gray and white m<~tter. In tile ~bnJm (a), most of the grvy molter Is concentrated superficially lr1 the cerebral oortex. The cerebrum also cont:alfiS more deeply situated Islands of gr.;ry matter (e.g., tile basal

c

HlltOioglulappe~ra,_ aftfle gray and whltl! mattl!t'

The grvy matuf Is m<~de up of tile cell bodies (perl/a1ryu or somoto) of n~rons. which are Interconnected to fonm neuronal networks (neuron hlstologylsdesa!bedon p.17411). Thewltltl!matter,ontheotherhand, cont:aim the processes (oxons) of neurons thatinterconnectdifferenUr· eas of the br.-aln .-arid splr~al oord. It derives 113 white oolor from the lipid content of the myelin sheaths. Many axons running In the Sime dlrec· tlon are colledl!d to fonm tlber p;ltilways or 170cts.llec.iluse tile proc:essifl!l of n~ral information begins in the perikaryon (som<~) and erlds at the synapse of tfle illiOO, tflese tracts .-are often named for tfldr sites of Olfgln and termination, e.g. tile COttlcosplno/ !Tact. The penlc;uya of tills

ganglia) rn iddltlon to other gray-matter structl.lres that are not specifically ~ddi'I!$Sed ir1 tlli$ CWC!nliew. The wfliW mattrr of tile arebnJm lies directly bene<~th tile cortex and also surrounds more deeply placed groups of gr<~y matter. S&tSon a addiiSonally shows part of tile Internal cll\llty system of the bl'illn, tile ventrkles (seep. 192ft). The gray/white matter arrangement is revel'lC!Id ir1 the ,Pr~~~l cord (b), in which the gray mattler Is placed centrally, fonmlng a butterlly-shaped figure, while the white mal:tef Is external to lt.

tract are located irl the arebl'ill oortex, and its amns terminate irl the spinal cord. This flow of lnfonmat!on Is also desa!bed macrosooplcally iS <1 •proJec:Uon." I.e., tile corticospinal tractPfl!I«Ufrom tile cortex to tile spinal cord.Tbe brain does not function as a "hard-wired computer." howeYC!I'. l.e;!rning proc:essn like tho.w that oc:tur during fXlbertv can alter the patterns of lmpcJise tr.-ansmlsslon wlthlr1 the br.-aln. An ellilmple Is tile physlal iWkwardfleSs that Is common during puberty, such as overturning a water glass at tile dlnnertable. As the lndMdwl mature.s, these iiCcidents become les$ frequent. Some time i' needed for po$ition sense tD adapt to changes In body size and proportfofiS.

173

NeurDGnatomy - - J. Introduction to Neuroanatomy

1.2

Neurons

Rl!a!p!Dr

Transmission

Terminal

segment

"'!(ment

"'!(ment

r-----~----~r--------------J~------------~~

Dendrite

Membr.me

potential

Direction oftr.~nsmlsslon -----+-

+40mV 0 -80mV

Elfcitatory

postsynaptic potential (EPSP)

1-R

~ Inhibitory postsynaptic

+40mV 0 -80mV

Action potential

Potential at the axon hillock

potential (IPSP)

A The neuron (nerve cell) The neuron is the smallest functional unit of the nervous system. It consists of a cell body, called the soma or perikaryon, from which two fundamentally different types of processes arise:

• Dendrites: Dendrites are called the rereptor segment of the neuron because they conduct impulses to the cell body that they have received at synapses with other neurons. One neuron may have multiple dendrites, which may undergo very complex arborization to increase their surface area (see q. Dendrites, unlike axons, are not insulated by a myelin sheath. • Axons or nerve fibers: The axon is the projecting segment of the neuron because It relays Impulses to other neurons or other cells (e.g., skeletal muscle cells). Each neuron has only one axon. Axons in the CNS are generally covered by a myelin sheath (the axons plus their

B Electron microscopy of the neuron The organelles of neurons can be resolved with an electron microscope. Neurons are rich In rough endoplasmic reticulum (protein synthesis, active metabolism). This endoplasmic reticulum (called /VIss/ substance under a light microscope) Is easily demonstrated by light microscopy when It Is stained with cationic dyes (which bind to the anionic mRNA and nRNA of the ribosomes). The distribution pattern of the Nlssl su~ stance Is used In neuropathology to evaluate the functional Integrity of neurons. The neurotubules and neurofllaments that are visible by electron microscopy are referred to collectively In light microscopy as neuroflbrlls, as they are too fine to be resolved as separate structures under the light microscope. Neuroflbrlls can be demonstrated In light microscopy by Impregnating the nervetlssuewlth sliver salts. This Is Important In neuropathology, for example, because the dumping of neuroflbrlls Is an Important histological feature of Alzheimer's disease.

myelin sheaths constitute the white matter). The myelin sheath may be absent in the peripheral nervous system (see details inC, p. 177). Either excitatory or Inhibitory neurotransmitters are released at synapses. These substances produce either an excitatory or Inhibitory postsynaptic potential at the target neuron. In this way the transmitters released at synapses modulate the potential in the perikaryon of the neuron. The excitatory and inhibitory impulses are integrated in the axon hillock. When the potential exceeds the depolarization threshold of the neuron, the axon "fires," i.e., the hillock initiates an action potential that travels along the axon and triggers the release of a transmitter from its presynaptic knob (bouton). Although this simple characterization applies to most neurons, connections in the CNS can be much more complex than described here (see C, D, and E).

Nuclear po~

Golgi apparatus

Rough endoplasmic ~culum

174

N•urotubules •nd neurofllaments

Neuroanatomy - - 1. Introduction m Neuroanatomy

Presynaptic membrane

&1' < - - - Preynaptic ll!rminal (bouton)

Postsynaptic membrane

~;;~==~~ij§i~~~~- Synaptic cleft Presynaptic memblillne

Basic forms of the neuron and its functionally adapted variants The horizontal line marks the region of the axon hillock, which represents the initial segment of the axon. (The structure of a peripheral nerve, which consists only of axons and sheath tissue, is shown on p. 180.) C

a Multipolar neuron (multiple dendrites) with a long axon(= long transmission path). Examples are projection neurons such as alpha motor neurons In the spinal cord. b Multipolar neuron with a short axon (=short transmission path). Examples are lnterneurons like those In the gray matter of the brain and spinal cord. c Pyramidal cell: Dendrltesarepresentonlyattheapexand base of the triangular cell body, and the axon Is long. Examples are efferent neurons of the cerebral motor cortex (see pp. 180 and 200). d Purkln)e cell: An elaborately branched dendritic tree arises from one circumscribed site on the cell body. The Purklnje cell of the cerebellum has many synaptic contacts with other neurons (see p. 241). e Bipolar neuron: The dendrite arborizes in the periphery. The bipolar cells of the retina are an example (see c, p. 131). Pseudounipolar neuron: The dendrite and axon are not separated by the cell body. An example is the primary afferent (sensory) neuron in the spinal (dorsal root) ganglion (see pp. 180,272, and 274ff).

D Electron microscopic appearaiiCI! of th11 two most common types of rynaps11 In th11 CNS Synapses are the functional connection between two neurons. They consist of a presynaptic membrane, a synaptic cleft, and a postsynaptic membrane. In a "spine synapse" (1 ), the presynaptic terminal (bouton) is in contact with a specialized protuberance (spine) of the target neuron. The side-by-side synapse of an axon with the flat surface of a target neuron is called a parallel contact or bouron en passage (2). The vesicles in the presynaptic expansions contain the neurotransmitters that are released into the synaptic cleft by exocytosis when the axon fires. From there the neurotransmitters diffuse to the postsynaptic membrane, where their receptors are located. Avariety of drugs and toxins act upon synaptic transmission (antidepressants, muscle relaxants, nerve gases, botulinum toxin).

Axodendrttlc

Amaxonal

E Synaptic patterns In a small group of neurons Axons maytenminate at various sites on the target neuron and fonm synapses there. The synaptic patterns are described as axodendrltic, axosomatic, or axoaxonal. Axodendrltlc synapses are the most common (see also A). The cerebral cortex consists of many small groups of neurons that are collected Into functional units called columns (see p. 201 for details).

175

1.3

Neuroglia and Myelination

A CelluftfleneurogR;alntheCNS Neuroglial cells surround the neurons. prollldlr~g lflem With structur<~l and functional support (see D). Vario~JS staining metflods are used in light microscopy for moAa or less sdecdvely defining specific porlioru of the n~rogllal cells:

t b

Cell nudel demonstrated 'toith a baJic Jt<~ln. b Cell body demonstr.tted by sllveJ lmpregrliiUon.

;a

Neuroglial cells constitute the v<~st majority of cells lr1 the CNS. outneurons by ipproxlnn<~tely 1o-to-1 (1 trillion n«~roglril ails tb 100 billion neurons by recent estimat2.s). The neuroglia have an ment!al role lr1 supportlr~g the function of lfle neurons. For eMmple. artrocytes ibsorb excess neurotrilriSmltten from lfle eldracellular milf~. helping to malrlbln a constant Internal env1ror1ment. While neurons are, <~lmost without exuption. permanently post-mitDtic some n~rogllal cells continue to divide lflrooghout life. Forlflls re.1son, moJt primary brain tumors origlnrte from neuroglial cells ;md are Nmed for lflelr morphologle<~l similarity to nornn<~l neuroglial ulls: <1strocytoma. oligadendroglionn<~. and glioblastonn<~. Develosunermlly, most neuro· glial cells arise from the same progmltor cells
a

Fibltlllry ~e

b

Node ofltill'fler

S~n

uUnudel

I Mrellrlab!ld-ln tile PNS Most axoos In lfle pe!'fpheral nervous system are Insulated by a myelin sheath, although unmyelinabed axons are also faund in lfle PNS (see C).

176

The myelin shei1h enables Impulses to travel f.lster ilor~g lfle axon as they 'jump• from one node afltllnvler to the next (saltatory nerve conduction). ralfler than travel cantinuowly as in an unmy!!!linated ax~m.

Neuroanatomy - - 1. Introduction m Neuroanatomy

Cl\IS

Nucleus of a Schwanncell

Schwanncell with a myelinated

.,.,n

---

-------~

Axon

C Myelination differences In the PNS nd CNS The purpose of myelination is to insulate the axons electrically. This sig· nificantly boosts the nerve conduction velocity as a result of saltatory conduction. While almost all axons in the CNS are myelinated, this is not the case in the PNS. The axonsofthe PNS are myelinated in regions where fast reaction speeds are needed (e.g., skeletal muscle contrac· tion) and unmyelinated in regions that do not require rapid information transfer (e.g., the transmission of muscle spindle and tendon tension sensation). The very lipid-rich membranes of myelinating cells are wrapped around the axons to insulate them. There are differences between the myelinating cells of the central and peripheral nervous sys-

terns. Schwann cells (left) myelin ate the axons in the PNS, whereas oligodendrocytes (right) fonm the myelin sheaths in the CNS. Noll!: In the CNS, one oligodendrocyte always wraps around multiple axons; however, Schwann cells ens heath either one myelinated axon or multiple unmyelinated axons. This difference in myelination has important dinical implications. In multiple sclerosis, the oligodendrocytes are damaged but the Schwann cells are not. As a result, the peripheral myelin sheaths remain intact in MS while the central myelin sheaths degenerate.

D Sum11111ry: Cells of the cent111l nenrous system (CNS) and perlphe111l nervous system (PNS) and their funcUonallmporl:ilnce c.lltype

Neurons (CNS and PNS) (seep. 179)

1. Impulse formation 2. Impulse conduction 3. Information processing

Cil..lcalls

Astrocytes (CNS only) (also ailed mocroglla)

1. Maintain a constant Internal milieu In the CNS 2. Help to form the blood brain-barrier 3. Phagocytosis of nonfunctlonlng synapses 4. Scar formation In the CNS (e.g., after cerebral Infarction or In multiple sclerosis) 5. Absorb excess neurotr~smltters ;md K+

Microglial cells (CNS only)

Cells specialized for phagocytosis and antigen processing (brain macrophages, part of the mononucle~r p~ocyte system); secrete cytokines ~nd growtll f01ctors

Oligodendrocytes (CNS only)

Form the myelin sheaths in the CNS

Ependymal cells (CNS only)

Line cavities in the CNS

Cels of the choroid plexus (CNS only)

Secrete cerebrospinal fluid

Schwann cells (PNS only)

Form the myelin sheaths In the PNS

Satellite cells (PNS only) (also ailed montll! cr//s)

Modified Schw~n cells; surround the cell body of neurons In PNS g~glla

177

1.4

Sensory Input, Perception and Qualities

Jolnb,lldn.

St.la.t muscle

,._.etllmusde

/ Soln.ilblmOIOr

ftbers

/ CNS

/ A Sdlenmfc dlaQr..m ofrnfonnaUon flow In tfle nervous system We begar1 this chapttr (p. 172) by dMdlng the nerwiiS system Into the CNS arid PNS. The nerv~~UJ $YJtc!m c~n also be divided bi!lled the di~ tfonoflnformatfonflow. Nervesthattr.lnsmltlmpulsestowardthebr..ln or spinal cord are called of(l!rent fibers (left), and nei'YI!5 that transmit Impulses ilWIItf fllMn the brain or splr~al cord are called ~fibers (right). The temu a~rent and efferent are ;also used within tfle CNS w desafbe tfle connectlotu between nudei. The rtructure of the neuron Is lmporunt In this scheme, bee<~ use the dendrlt:fc tree and Its proce.sses are.aft'erentwhile.w~nsand the
I SpKiill MniiOI'Y qu;llltfs Tbe ability of the ne!VOUS <~nd sensory syrtem ID peraive a great variety of stimuli is called sem:Gifon. This communication with the envl· ronmern:ls mediated byspedallz:ed pm:ep!Uill organs!Ntare located .tt anatomle<~llydef!ned si1zs.. Tbe special sensory qualities indude taste, smell. Ylslon, hearing, and the sense of balaoce. All of these sensory pm:eptlons are tr.msmltted m the CNS by cr<mlal nerves.

178

Gllnds. smooth muscle. ardKmuscle

somot1c and autonomic (Yisceral, veget<~lfve) nervous system (uppef and lOwe!' parts of the diagram, respectively). Tbe somiltlc nerv~~~a system is l'ftporuible for communication be~ the organism ;and ib envi-

ronment. and It coordlr~atts locomotion. The autonomic (vlscer.~l) nl!f'vo~a system coordinates the functfon of the Internal organs. Using the

scheme pictured here, we can subdiVIde axons, as well as nerves and~ ber tracn. inw four dilli:!rent modalities: som~tit afferent. $0m
Neuroanatomy - - 1. Introduction m Neuroanatomy

Vibration

Touch, pressure

Temperature

Pain

c

General sensory qualities A basic distinction is drawn between external perception (exteroCI!ption} and intEmal perception (proprioCI!ption} depending on the source of the stimulus. Because the stimulus in exteroception comes from the external environment and is perceived by "exteroceptors" in the skin, this sense is also known assuperffdal sensation. In proprioception, the source of the stimulus lies "deep" within a muscle, tendon, or joint(information on the relative position of the body parts), and so this mode of perception is also called deep sensation. Moreover, two sensory qualities are distinguished in exteroception, which may both be perceived at the same location: (1) epicritic perception (light touch, vibration, two-point discrimination) and (2) protopathic perception (pain and temperab.Jre), which includes an emotional component (pain is distressing, for example). Exteroception, then, is largely a conscious mode of perception that is mediated by the gracile and cuneate fasciculi (epicritic) and the anterior and lateral spinalothalamic tracts (protopathic). Proprioception, on the other hand, is largely unconscious and is integrated chiefly by the cerebellum.

Deep sensation (proprioception)

Testing superfldal sensation: • Vibration sense: tested with an alternately vibrating (64 or 128 Hz) and nonvibrating tuning fork, which may be placed on the shin, for example. The patient should be able to perceive the difference between the vibrating and nonvibrating states. • Pressure and touch sensation: The skin is touched with a cotton swab. • Pain pera!ption: The skin is pricked with a sterile hypodermic needle. This test can also be used to test two-point discrimination. • Heat and cold sensation: Test tubes containing wamn or cold water are placed in contact with the skin. Testing de11p sensation (proprioception): With the patient's eyes closed, the examiner moves the distal phalanges of the toes, for example, and asks the patient to describe the position of the digits without looking at them.

Tr.msductlon

Alpha motor neuron

Gamllkl motor neuron

Action potential ~~~=--- Annulospiral

endings

\ -+~-- Worldng muscle

ReceJJ!or potential

Muscle spindle

...,..........,...-.~c-....,._----!~r-- Wortdng

~ ~

muscle

lbfiber

Tendon sensor

Golgl tendon organ

D Receptors In the muscles and tendons The receptors In the muscles (muscle spindles), tendons (Golgl tendon organs). and joints (not shown) give the brain Information about the position of joints, muscular force, and movements. This Information Is known collectively as proprtoaptlon. For example, we know when our hand Is clenched Into a fist even when It Is behind our back. The brain receives additional Information on tile position of the head and limbs from the vestibular apparatus (sense of balance), the eyes, and mechanical sensors (mechanoreceptors) In the skin.

•

Transduction

b

E Different types of sensory receptDrs Proprioception as described above Is mediated by specialized peripheral endings of primary sensory neurons whose cell bodies are In spinal (dorsal root) and cranial sensory ganglia. other (exteroceptive) sensations Involve receptor cells that are slb.Jated within special sense organs. These receptors can be neurons with axons that synapse onto secondary neurons (as In a, an olfactory receptor slb.Jated In the olfactory epithelium, which sends Its axon Into the olfactory bulb (CNS]). Other specialized receptor cells (b, vestibular hair cell) may have no axon, but Instead participate In local synapses with neurons that, In turn, transmit the Information to higher centers. The neurons that synapse with vestibular hair cells have cell bodies In the vestibular ganglion. llhe central processes of these ganglion cells travel In the vestibulocochlear nerve to the bralnstem_

179

1.5

Peripheral and Central Nervous Systems

A~~------------~-

tls:sue

Ej)lneurio.m

A Pertph~nlnen.e lnformiltlon travels In !he PNS ;!long nerves. which are the equiY
fibers and is the.-efore c:.1lled a mixed n-. Afferent ;and efferent fibers may be myelinated or unmyelinated (lacklr~g a myelin sheilh).ltwlll be reCA~IIedthatthe pe!'fpheral nerves ilre myellnillled bySchwann cells (see c.p.177). ~The perikarya of neurons In !he PNS are locmd In gar~gllil (see B).

B CilngiTa

As noted above. the perikarya of neurom In !he PNS are loc.Tted In giln· gila. Two main types of gangllor1 Ciln be distinguished: ill SpfrMig;~ngl;iarelocatedatlhedonillrootofsplnal nen'I!Sandcon·

tlln pseudo unipolar neurons. These neurons convey srnsoryfn[ormatloll from the periphery (e.g .• pressure, temperature. pain) lflto the spinal cord. where the impulses are relay!!!d to anolher neuron. The perlkaryor1 has aT-shaped connection with !he axon (see C. p. 175); thus. no synaptic relay lr11he spinal gar~gllon. Since the perlpherill process recel'ves sensory Impulses, this neuror11s c:.1lled a pmnafYaf· f~ ne~~ron. The sensory craniaJ.n- ganglia also contain pseu· dounlpolilr neurons, wfllcfl corTe:Spond functfonallytothe spin ill ganglia. b Autonomic g~ngla are part of the autonomk n~ system. The efferent fibers to the (int!!maQ org;ans are n!l•d in lhese gangl~ (see p.316).

•

lntr.~mur.~l gilllgllllr~lhe Intestinal mil (nots'-n) are part of!he en·

ller1c nef'VOClS system (seep. 324).

b

180

Neuroanatomy - - 1. Introduction m Neuroanatomy

Interneuron

..Vflf--+-:-..,...,.'---'\-- Tertiary afferent {sensory) neuron

\ \ ,er-- - - - - Se<::ond;lryafftnnt (sensory) neuron

Lower motor neuron

C SomatDmotor Integration This greatly simplified circuit diagram shows how the sensory and motor systems work together during ordinary activities. An example: PlacIng the foot tentatively on the lower rung of a ladder to see Ifthe ladder Is stable Initiates a flow of signals through a chain of neurons (the sensory neurons are shown In blue, the motor neurons In red). The sensation of the foot touching the rung Is conveyed by the primary sensory neuron to the spinal cord. This neuron synapses with a secondary sensory neuron at the upper end of the spinal cord (dorsal column nudel), which synapses with a third neuron In a specialized nucleus In the diencephalon. From there the Information Is relayed to the sensory cortex. Inter-

neurons In the brain then give rise to How of Impulses from the sensory cortex to the upper motor neuron In the motor cortex, which relays the motor command down to a motor Interneuron. Finally this Interneuron activates the lower motor neuron, which causes the muscle to contract and enables the Individual to start climbing the ladder. Note: Most diagrams omit the lnterneurons and show only the first and second motor neurons, which are called the "upper motor neuron" In the cortex and the "lower motor neuron" In the spinal cord. The distinction between these two neurons Is very Important dlnlcally: A lesion of the upper motor neuron causes spastic paralysis, whereas a lesion of the lower motor neuron causes flaccid paralysis (see p. 343 for details).

181

1.6

Nervous System, Development

A Nanllllllnllll neunlCNSt (•rWolpert) The tissues oflhll! nerw~us sysllrTI originateem bryonially ftGm the dot· sal sumce ectudenn. The notodl.ord In the midline cfthe body lndue25 the fumt•lon of the neural plat, which lies~ the notDchard, ;llld of the neun~l cruts. which are latrr.J to the notodlord. With further dewlopment. the neural plat deepens at the center to fonm the neural groove, which is ftanll2cl on eadl side by the neural folds. I.Jd:l!!t the

Surt.c. edDd"""

~Nolllchold

g~deepensandclosestofonmtheneuriltube.whlchslnksbeneath

the ectoclenn. The Mllf'GIIIlbe Is the structure from which the centnl ne~~m (CNS~e br;oin and lf)inalw~~loPJ (further development of the spln1l cord Is shown In I. further brain development In D). Fa!lure ofthe nlllral g . - tn close completely wiiii~YW an anomaJgus deft In the wrtebral column. known as 5plna blfldo. The idmJnlstratlon offullc acid to potentia Imothers around the tlme of conception can reduce the incid'"ce of spina bifida by 70 lt:. ulls that migrate from the MIIIVI crat develop Into nr1ous structu res,lndudlng cells ofthe perlphenl nerYOus system (PNS) such as Sc:hw.ln n cells and the pseudounlpl)o Jar cells ofthe spin~~I ganglion (see C).

Neu,.lfolds

---

~

~ ;

~..lci'HI:

£pldermll

llcofplft Alarplm lone of

outDnomlc

11au1 plm

ne.......,

Floorplm II

~..(;!!:)"'E::::--- llcofpllte

~ulfng~ llllnS ofthe dcrsll roatlnt!t~ sphtlg~~~gllon

--+..__- /hrple Zoned ----~~~ alltonomk:

n-..ra"'s

I

~on afthe nanltullelnthe spiMI Clift! during

dewla,_nt

Cross-section, superior view. • Early na~ral tube, It lnt«medlill! stage, c idult spina ICORI. The ""'rons that form in the basal plat are ~rent (motor~). while the neurons t~ form In the alar pllte are afferent (HnDy neurons). In the future thoradc,lumbar, and sacral spin~ cord, there Is anotherzane between th.em th• glws rise tD symJNthetic (autonomic) effvent na~rons. The roof plate and floor plate do not form ne.nons.

182

C Dewlopment fll il pertphii'IIII'Mirw Afferent aons (blue) and efferent axon• (red) sprout separuly from the neuroml cell bodies during early embryonk d~lopment. Primary afferent neurons de¥elop In the spinal gang lion, and alpha motor na~rons dtwlop from the bat~l plate of the spinal CORI. IIJ The i~meuron' (bl"k), which runctionally interconnect the sensory and motor neurons, develop at a I~ stage.

il

• TelodlenQ!Phallc - - - - ,

sum

TelenoepNion

Pons

D Develapmentottflebnln • Embryo with a gre~~tert length (Cil} of 10 mm at the beginning aftbe se
b Embryo with aGlof27 mm neartheet~d of the second month of development (end of the embryonic period). The telencephalon and d'ter~cephalon h;ave et~larged. The olfactory bulb Is developing from the teler~cephalon, ;md the primordium of the pltult.arygland Is dew!~ lng from the dler~tephalon. ( Fetus with a (il of 5l mm ir1 appraximately the third mor1th of development. By this mge the telet~cephalon has begur11» cover the other br.illflilreas. The Insula Is still on the brain S1.1rfa1:2 but will subsequently be ccwered by the hemispheres (comp;are With d). d Fetus with a (il of 27 em (270 mm) in approximately the $CM!Ilth month of development. The CEJ'ebrum (telet~cephalon) has begun to develop wel~deflned gyrt .ilnd sukl.

development proC!eds.

E Bra'h veslcleund their derf1111tlves The aanlal end of the neural tiJbe exp;~nds to fonn three primary brain vesicles for the • forebrain (prosencephalon}, • mldbriln (mesencephalofl), and • hindbrain (mombencephalon). The telencephalon and diencephalon develop from the prosencephalor1. The mesencephalon gives rise 1» the Sl.lperior and lnfertor oolllcull .and related structiJres. The rttombencephalofl difl'fftnliates into the pons, cerebellum, and medulla oblongat.a. The poru arid cerebellum 01re also known collectively as the t!lftentl!Ph· alon. Some Important rtructures of the adult brain are listed in the diagram at left to illuttrate the derlvates of the brain vesldes. They can be traced b
183

1.7

Brain, Macroscopic Organization

P;uletll A leltlmr<~lllfewofthelnln The cerebnJm 1~ dMded macroscoplully Into fourlobu:

lobe

• Frontallobe • P;ariet~llobe • Temporal lobe • Ocdpltallobe The surface contocJr~ of the cerebrum ired~ flned by amvolutfons (gyri) <md depressions (sulci). An ex;ample is the «ntr.ll sulcus. which separates the precentral gyrus from the pOlt· central gyrus. The~ two gyri ire function· ally Important beuuse the ~/ gpus Is conc:emed with ~t~~lunury motor activitywhi1e the postrentro/li)'I'IIS Is concerned with the conscious perception of body sensation. Deep Within the lateral sulcus~ the tnwlor/obe, often ulled simply the Insula (see B. p. 173). The sulci are narrowed and compres~ In brain Nl!rna (excessllle fluid iccumulatlon In the briin), but they are enlarged in brain otnJplty (e.g .• Alzheimer's dist'ase) because of tissue loss from the gyri. The brains that ire available for dlssectSon In medlul school ccurses f~ quently manifest signs of br01in atrcphy. Often the <~trophy Is predominantly front<~ lin males and predomlnantiy ocdpltal In females. but the reason for this disparity Is unknown.

Frcnt31

lobe Tozmparal lobe Litlenil

sllcus

FI'Cintll lobe

B Baul view aftfle braTn The spinal cord has been sectioned In Its upper cemul portion. This view demonstr.iltes the sites of emergence of most of the cri· nial ni!IWS (yellow) from the brainstzm (see p.66ff). The frcntal lobes, tempor.ill lobes, pons. medulla oblongata, .ilnd «rebdlum ire the principal structures that un be ldentitled on the base of the br.rin. This view cl~rly di$· play3 the two hemispheres and the long/tudlnol O!ll!brallfssure between them. The gyri wry conslderibly rn different rndMdwls, ind ewn the convolutiam of a single br.rin may show marked slde·to-slde dlfl'eren«S, presumably due to the specialization of the hemispheres.

184

~~I

anllralftssure

Medulla oblongata

C Mld!I.Jgltt.11 sedfon of the br.ll:n showfng the medl;~l sumce of the rTght hemlsphThe brain hils been split along the langitudin;~l arebralli$Sure. Deveiap· mentally, the brain can be divided Into several major p;1rts (sti! p. 183). all of which are visible lrlthls section: • Telencephalon (cerebrum) • Diencephalon • Mesenczpbalon (midbrain)

Oa:tpltaiJ

audal

• Poi'IS

• Medulla oblor~gata • Cerebellum The medulla oblongata is continuous inferiorlywith the spinal C1lrd, with no definite anatomical boundary between them. The mesencephalon, pons, and medulla oblongata ire collectively referred to as the brain· S!l!ln based on therr common embryological and functional featunes. The brainstem lie$ near the anterior surface of the cerebellum.

D Tenns of loc:lltlan and dtrKUon In the c:entnl nl!f'VOIIs symm Midsagittal section viewed from the left side. Repeated references are made in subsequent units to twa different axes of the brain: the Meynett

aJtls, ~Mllch Is used to designate loc.atlons In the bralnstem, and the Fort/ aJtJs, which describes the topogr01phy of the diencephalon .ilnd telen-

cephala B. • The Meynert axfs (1) p.iiSses through the brilfnstem and COITI!.Sponds roughly to the longitudinal body axis. • The FGNI axlJ (2) runs horizontally through tile diencephalon and telencephalon.

The fDIIowing dlaptl!ts on the CNS begin with the cerebrum and pro· ceed downward to attlef brain structures and the spinal corcl. Our ap· proach to CNS topography also proceeds from outside to Inside, followIf~!~ the order In ~Mllch the structures are encountered 11'1 a drssectfol'l. Neuro.tnatomy is partia..larly challenging bec.auseWI! cannot directly in· fer the function of a structure from Its appearance as we can v.ith mus·

de tissue, farex.ample. Ourpresentation oftheCNS therefor!! ends with i chapter on functional systEms. In describing tile functional systems, we will use a perfpheral·to-cent:ral approach (I.e., from the simple to the camplex) so that the reader may better undentllnd the path fDIIowed by a stimulus from its source to its v.arious relay stations in the CNS.

185

Neurot~I'H1tomy - -

2.1

2. Meninges oftlw! Bl'tlln andSplnGI Cord

Brain and Meninges in situ

lnnN _ _ __..,...:;·'' table

"

Diploe--·' ~

l
sklU!> ~llilcula

(OP'!fl) -

Aradlnald

-f-;- - - - - - '1'.1__ .

----,,.--...;_-~t::;~ll!

granulations Ostlaaf -~::-
lx'ldg.,glldns

Qlnftuencz

af me sin UII!S .,..,....__ BranttlKafmlddle cerebral artery

.,r-==r-- - Cetebralsumce wtlll pia mmr ~.....,j'-41ooi,drt:l--

Brldglng\dru (s~ai'Ebral

wns Just be/ore the,. iffit« me

sl4l'!f!Or sadtt
sinus) b

A Brain and menl'nges rn situ Superi~:~rview. a

The calvaria has been I'I!MCM!ld, and the superior sagit· tal sinus and In li!Wr.!llacuBae hi!Ve been opened; b Thedur.1 mater has been removed from the left hemisphere. ;md the dura ;md irachnold hil\le been removed frcm the right hemisphere. The brain and spinal ami al'l! COIIen!d by membrarleS nlled meninges, which form a sac filled with cerebrospinal fluid. The mmlnges are com· posed of the following three liyen: • Outer layer: The duro matw (often shortened to "duri•) Is a tough layerofcollagenousconnect!~Ussue.ltconslst:softwo layers. ,min· ner meningeal layer and an oub!r endosb!al &aye.-. The petiosteallayl!!r adheres firmly to the periosteum of the ulllarla v.ithln the cranial c.Mty. but It Is eisy to sep01rare the Inner liyer from the bone In this reglon,le.avlng It on the cerebrum as Illustrated here (a). • Middle layl!!r: The oradmold (arachnoid membrane) Is a translucent membr.~ne through which the cerebrum and the blood ves5els in tfle subirachnold Spice c
186

The arllchnold lind pia are collectl~ly ailed the kpttlmt!llfnges. The spice between them, ailed tfle liUbirachnoid sp;ace, is filled with cerebrospinal fluid and mvelops the brain (see C. p.191).1tcontalns the major cerebral irrerles and the supertldil cerebral ~lns. which driln chiefly through 'bridging Wins• Into the superior s.~glttal sinus. The dura mater ill the midline forms a double fold between the periosteal ind menlnge;rllayen !hit encloses the endothellum·ltned superior s.~g­ ltl31slnus (see 8, p. 254). which h;as been opened In the rtlusu-atlon. Inspection of the opened sinus ~Is the ar.achnold gr.anul.tttons (Pacchionian grarlulations, arachnoid villi). These pro!Niions of the arachnoid ire sites for the reabsorption of cerebrospinal fluld (see A. p.194). Arichnofd granula!Sons are pirtlcularly .abundant In the li!Wr.!llacunae of the supertor s.~gltul sinus. The dissection In a shows how the ml~ die meninge;~l artery i$ situated betwl!en tfle dura and al\'iria.llupture of this vessel causes blood to acaJmulate betwHn the bone ind dur.1, fomnlng an epidural hernatomi (seep. 262).

sag!Ualslnus

Llllenllventlicle, a-hom

Telencephlllll'l, mxrtlllobe

lllll!nl!lllriallr fwamen

s~

Tlllrdwntr!de

IJI!Jeral wntJ!cle

Sptwnopariml sinus

Telen«Phalon, llemJ)Or.JIIobe

Supe"lor

~lsfnt~~

Pt!Utlr'y

Tl'answ~se sinus

CM!mowslnus

Pons CAnbt!llum lnfi!rfor ~lsfnt~~

B.Biar plexus

Sigmoid sinus

B PrD)er:tSon of Important bl'llln ttruc:tures onto the tlalll Anterior view. The Iargen struct\JI\!S of the ~brum (telencephalon) are the frontal and temporal lobes. The f.llx anbrl sep;~rates the two cerebral hemispheres In the midline (not Wible here). In the bralnstem,

Super!ors.1glltll - - ---:-=-sinus

we can Identify the pons .and medulla oblongat.a on both sides of the midline below the telenceph;llon. The superior sagitt."ll sinus and the paired sigmoid sinuses can also be seen. The anterior horns of the two liltl!ral ventricles are profectl!d onto the forehead.

-:or

~---=-----"o:...=:,.--------=- :---:7=-....,.,--r-~

aqueduct

~~--~~--+~~-,-~~-~~ OlliS

c

PrD)er:tSon of Important bl'llln ttnld:Ures onto the tlalll IRft lateral view. The relationship of spedflc lobes of the anbrum to the aanlal fossae can be appreciated In this lltew. The frontal lobe lies In the .antel'for cranial fossa, the temporal lobe In the middle cranial fossa,

Str.atgrtslnus Fourth wnllide

and thecerebellum in the pDS!J!fiOI'cranial fossa. The following dural~ nous sinuses can be Identified: the superior and Inferior sagittal sinus, straight sinus, tr.msverse slmiS, sigmoid sinus, Cil'lleiTIOUS sinus, superior and Inferior petrosal sinus, aDd ocdplt.al sinus.

187

Neurot~I'H1tomy - -

2.2

2. llllenlnges of tiM! Bl'tlln andSplnGI Cord

Meninges and Dural Septa

Site of4!!lry ln!D tt.e s upertar Silg'lttllsl'lur.

---....,...----~-=,......:,....-- SUpertar

O!l't!llralwlns

.):~~--l'lftrfor

O!l't!llralwlns

A ll'illn rn situ wttfl tfu~dul'il p;u1Sally dlli4!ctd from tM
the underlying ar;achn~id and pia m~tel' on the briin. Be· cause the ir.ldtnold Is so thin, we can see the underlying subir;achnotd sp;w:e ;md the YeSsels th~ lie within It (see C). The sub~rilchnold SPice no longer COilt'llns cerebrospinal fluid at this stilge of the dissection and Is therefore collapsed. Before the superficial cerebral veins tmnl·

nate In the sin liS, they leave the subilrachnold Spi!cefor a short distance and course between the neurothelrum of the arllchnold and the menu~ geal • of the dura to the superior sagittal sin liS. These segments of the cerebral vdns ire ailed brldglng wins (see C). Some of the bridgIng veins, especially the lnferfor cerebral veins, open Into the tr.rnsverse sinus. lnj'Ury to the bridging velru leilds to subdural hemorrhllge (see pp. 191ind 262).

Inferior

!l
~ ll-~slnus

Dllphragrna sellae

-::tit· 'J I

Stralghtslnw

Oinfklenae of1fle sinuses

~--~~ ~ Ocdpltalsl'lur. --

Tenmtlum

~·· I l>uri!IAptl IJ!ft anterior oblique view. The brain hils been shelled out oflu cavity to demonstrate the durlll septa. Theflllxcerebrlappears as a fibrous sheet that arisa from the criJta galli of the ethmoid bone and $C!SJilrilt2.S the two cerebral hemispheres. At. Its site of attu:hment to the calvirla, the falx cerebrl exp;rnds to aa:ommodate the supelfor sagltt
181

here). The ternorlum cerebelll filru out Into the grooYe between the cerebrum ilnd cerebellum. ¥>flllethefalxcerebelll sep;rriiW the two hem f.. sphel'tl of the certbeUum. Its root transmitS the occipital sinus. Because the dural septa are rigid strudUn!$, portiamofthe brain may hec-nlate beneath thelrfreeedges (see D). The bralnstem pi!ssesthrough an opening In Ule tentorium cerebelll called the tentorial notx:h.

SuJM!riar saglttalsl'l~a

Dur.unater, petfosteallayer

fmll.nry

win Sc.l!p wins

Olplae

Inner foible Lm!rallacuna v.1th aram naid !11111\UII(iol'l$

(aradll\i01do1111)

Dununater. menlngeallly!f

Sinus

Falx

endothelium

areblf

Br!dgilg vein

C Rclltlol'lllhlp of the meninges to the alnrbn

Coronal section through the vertex of the skull. anterior view. The endosteal layer of the dura mater and Ule penosteum of the skull are fused together (the periost2allayet" of the dura mater). e.-ach layl!t mn· sbtlng of a tough meshwork of fibrous tissue. At. some sites the dur.1 fonms septa that dip Into Ule fissures separ;rt!ng different br.~ln regions. In the vertex region pictured here, Ule septum consists oftflef.abc cerebri (other septa ;rre shown in B}. located within the dur;~, between Its endosteal and meningeal layers, are the principal venous channels of Ule brain, the dural ve11ous sinuses (e.g.,Uie superior sagittal sinus). Thelr walls .ilre composed of dura and endothelium. Arllchnold granu· lations protrude frvm the subar;~chnoid spatt' into the superior $i!git·

;a

D Patenlfllsltes of brll'n hcmTIItTon benellth the free edges of the meninges Coronlll section, .iln1ll!rtor view. The tentorium cerebell! dMdes !he cr.il· nial cavity into a supratentorial and an infratentorial space. The telen· cephalon Is supr;rtentorfal, and the cerebellum Is lnfratentorlal (1). Be· cause Ule dura Is composed of tough. collagenous connective lhsue. It tre.iltes ll rfgld Intracranial framework. As .il result, a mass lesion Within Ule cranium may displace the cen!br.al tissue and cause portions of Ule cerebrum to become entrapped (herniate) beneath the rigid dural septa (= dupllcatfofl oftfle meningeal layer of the dura).

a Adll hemlltlon. This type of herniation is usually caused by generalized br<1lr1 edenn<~. It Is a symmetrical herniation In whkh the mid· die ;md lowe!' portions of both t:empor<~llobes oftfle cerebrum heml· ate down th~gh tlletl!ntorlal notm, exerting pn!S$Ureon1he upper

tal sinus. These projectklru are channels th~gh which cerebrospinal fluid from Ule subar<~chnold space can be re<~bsorbed by!he venous system (det;llls on p. 194f). They can produce pitS In the Inner table of the skull (granular fvveolae, see p. 8). Aschematic dose-up (b) shaw$ the relationship of the plit-ar<~dlnold, which contalfiS the slit-like subarachnoid space. This space Is subdivided b:Y 01rachnold tribeculae Ulat extend from Ule outer layer (arichnold} mUle Inner lilyer (pia mater). At iU boundary with the dura, the arachnoid is covered by fl~t cells which, unlike other menlnge<~l cells. <1re joined together by •tight junctions" (neurolhellum) to aeate a diffusion birrler betweenlhe blood and cerebrospinal fluid (seep. 196).

portion of the mldbr.~ln (bilateral uncal herniation). If the pmsure persists, It will force Ule cerebellilrtonslls through 1he foramen magnum .ilnd also compress the lowerpartofthe bralnstem (tonsnrar herniation). Beuuse l'l!!'IPiratory and circulatory centen <~re loated in the br.alrutem, this type ofhemlillion Is life-threatening (seep. 231). CoriComltant vascular compression m;ay cause br<~lnstem lnf.arctfor1. b Lltl!nll hemlltlon. This type Is caused by a unilater.al mass effect (e.g., from a brain tumor or intr.lcranial hematoma), as illustrated here on the right side. Compression of the lpsllilteral cerebr<1l pedurtcle usually produces contr<~lat:er<~l hemiparesis. Sometimes. the herniating meslobasal portions of !he tl!mpor.illlobe press tile opposite Cfftbral peduncle against the sharp edge of the tentorium. This damages the P'iramldal tract a!x~Ye the level of Its decussation, causing hemiparesis to dewlop or1 the side opposite the Injury.

189

Neurot~I'H1tomy - -

2.3

2. llllenlnges oftlw! Bl'tlln andSplnGI Cord

Meninges of the Brain and Spinal Cord

Franl

-~g.---

A Blooch:upplyofdledununfter Mlclsagltt~l section, left lalef
l'lrletll br.~nch of mlckl~ meningeal artery Mastoid mndl of oa:lpltalartery

minor dinical import
>-----"':-<- - - Menl'lgeal branches (anll!rlot, posterior ~maldalnente)

B lnMI'VItl'on of the dura ITIItl!f' 1n the cnnlll cntty (aftenon

Lanz and Wilchsmuth) Superior view with the tart:orfum cerebelll removed on the rfght side. The intracranial menings are su~ plied by mmlngeal br~nches from all three dtvlslons of the trlgeml· nal nerve and also by branches of the vagus nerve and the first two cerYical nerves. Irritation of theie sensory fibers due to meningitis Is m<~nlfested dtnlcally by headache and reflex nuch~l stiffnes5 (the neck Is hyperextended In an attempt to relieve tension on the Inflamed menlngl!l). The brain Itself Is lnsensl· tive to pain,

190

Menl'llltlil br.Jnc:hes (ophthllmk
--...,.-,~

~:..,:..--Middle cnnl~lfusw ~~~-

Menilgealbnlnch

ormandibular dMslan

c

Meninges and thelrspalli!S Transverse Mdion ttl rough the alva ria (schematic). The meninges have two spaces that do not exist under 11011T1al conditions. as well as one physiological sp.;~ce: • Epidural sp.;~ce: Tills space Is not normally present in tne brain (contrast with E, which shows the physlologlcal epidural space In tne spinal canal). It develops ln response to bleeding from the middle me11fngeal artl!ry or one of ItS br.mches (artl!rlal bleeding). The~ blo~ separates the dura !Tiilter from tne bone. dissecting an epldu· ralspacebetweentnelnnertableofthecal· varia and tbe dura (epidural hernatcma, see p.262). • Subdural Sp.ilc:e: Bleeding from the brtclg· lng veins artlftclillly opens tbe subdural space between the meningeal layer or tbe dura mater and upper layer of the arach· nold mernbr.me (subdural hematoma, see p. 262). The cells of tne uppermost layer of

Allncnnalepldural sp;IC2aea12d by
fllt\l~lum'-...... ~ ~ ~ -Durammt Arachnoid-

~

•

Arachnoid

·

•

•

•

~·

~-•

trabec.Jiae

•

•

.

• •

• ·

•.

• ~

~ral(l)~--

•

AbnonNisubdural sp;~atcreatedby wnaus bleed'ng fram aruptt.n>d brlcfglngw'h (!lbd~l

•

hemorthage) Plarn;rter

~ral

Suholradlnold

~I

~rtery

s~ce

w'h

tile arachfiOid (neurothellum) are lnterconnec:ll!d by a dense network or tfght junctions, creating a tissue barrier (bla~-cere­ brosplnal fluid barrier). • Subarachnoid Sp.ilc:e: This physlologkally nonnal space Ires just beneath the .ilrac:h·

nold. It Is fllled with cerebrospinal fluid ;md Is 1nvened by blood vessels. Bleeding Into this Sp.ilc:e (subarachnoid hemanilage) is usually arterial bleeding from ar1 aneurysm (abr10!11lal drcumsa1bed dilation) of the basal cerebral.ilrtertes (seep. 262).

Penostalm

lk'III'Qlhe

vemlnlanal

Vl!nlral

(anltrlar) root Donal

~or) root

Donalramur. Vo!nlral ramus

E Mentnges rn the G'.Jnlal c.mty.1rld sptnal CAl IIIII

D lNMWHUedSon ttl rough the spiMI c:ord ;md Its meninges Cervical vertl!bra viewed from above. Caudal to tneforamen magnum, tne dura matersep.il· rates from the periosteum; i.e., the meningeal and perlosteillayen of !he dura mater sepa· rate from each oCher to define a physlologlcil space, the epidural space. Tills space Is occupied by fatty tissue and venous plexuses. The dorsal and ventral roots of the spinal nerves course wllftln the dural sac of the spinal cord and cnllecttvely form tne cauda equlna In tbe

Spin~!

Spin~!

pi~~

ll~nsJIIon

IOWI!r part of the s.1c (not shown here). The donal and mttral roots unlre wlthln a dural sleeve at the lntervertl!bral foramina to fonn tbe spinal ne~WS. Aftl!r the two roots have fused later.~! tc the spinal ganglion, tne spinal nerve emerges from the dural s.1c. The pJo moll!! Invests the surfaces of the brain and spinal cord In the Soil me fashion. The denticulate llgi· ments are sheets of pial ronnective tissue tnat pass from the spinal cord to the dura and are oriented In the coronal plane.

The periDStJ!um of the bones and tne mellingeallayerof the dura !Tiilter are fused together lnsldetheaanlaiC3111ty. Caudaltotheforamen magnum, howewf, lhe.se 1:\W layers of collagenaus ronnective tissue sepatabe from t'.i!Ch othef to form the epidural space. Due to the mobility of the spinal column, the periosteum of tile vertebrae mustbefu!eto mave relative to the dural sac. This is accomplished by the presence of tne epidural space, which exists physlaloglcally only within tbe spinal canal. It contains fat .arid venous plexuses (see D). This sp.;~ce has majclfclinical importance. as it is the compartment Into which epidural anesthetics are Injected.

191

3.1

Ventricular System, Overview

lmnhontrlclo

liaal-.

ends \'llmr.lopertu,.., affaurtll-.trtd~

A Oftntew rllthe wntliall1rsystlm and Important neighboring

m.ctures Left literal view. The wntrla.ilar system Is a grutly exp;~nded ind conWIIuted tllbe that repreMnts 111 upw~rd prolonglltlon ofthe central spinal Cinal into the brain. There are four maralllmllides. or Civities. fllled w1th cerebrospinal fl uld and lined by a specialized epithelium. the ependyma (seeD, p.197). Thefoorwnlllclesare ~follaws: • The two lateral wntricle.s, Nm al which communicates through an Interventricular furamen with the • third ventricle, which In tum commu nlcltes through the cerebral aqueduct with the • foorth venbicle. This venbicle communicates with the subir.tdlnold space (see B). The largestventricles are the lateral wntfldes, each ofwhich cnnsists Df ;m anter1or,lnferlor, and posterior hom and a centril part. Certain portions of the wntr1cular system an be uslgned to speclftc p~rb of the brain: thunterigr (frontiQ hom tD the fronbllobe Df the ~brum, the Inferior (temporal) horn tD the temporal lobe, the posterior (occipital)

192

hnm to the ocdpltillobe, the th lrd YM!Irlde to the diencephalon, the aqueduct tD ltle midbrain (me5encephalon), and the fourth wntrlde tD the hindbrain (rhombalcephalon). The anll:omlcal rellltlonshlr» of the ventr1culo1r system an 1lso be apprecllted In coronal 1nd m nsverse secti111ns (see pp. 292 If and 304ff). Cerebrospinal fluid Is formed mainly bythe choroid pii!XUS, a network Df wsHis ltlllt Is present til snme degree In each ofthe four ventricles (see p. 195). Another site of cerebrospiN Ifluid prod uctlon Is the ependyma. Certain dlseues (e.g., atrophy of br1ln tissue In Alzheimer's disuse and internal hydroaophalus) are charecterlz.ed by 1bnormal enlal\'lement nf the venbicu li r system and ue diagnosed from the size ofthe venbicles In seclloNIInnlges of the briln. This unit deals with the wntrlallar system and neighboring strucb.J res. The nen unit will tria the path of the cerebrospinal fluid from its pi'Dduction to Its reabsorption. The l~st unit on the cerebrospinal fluid spaces will de;ll with ltle specII IIDd fu nctlons of the ependymi, the tircumventricul~r grv;ons, ~nd the physilllllll!liC~I tissue barriers in the brain.

Anterior hom oflmrallll!nU!de

l'fneal

Right lateral

venttlde

utetal recus. ends In lateral <Jpertureof fourtllwntrkle

•

I Cast of tfle ventJfcul;r system t.!ft lateral view (a) and supel'for VIew (b). Cill!t spedmens are used tD demonstr~ the a~nnettions betwl!en the 111!ntricular avities. £olch lat· eral ventrlde communlcites with the dllrd ventrfde through ifllflter· ventrfcular foramen. The lfllrd ventricle a~mmunfcates Ulrough the ce· rebr.alaqueduct ~th the focJrttt 111!ntrfde In the rhombencephalon. The

lhai;Jmus

ventrlcularsystem hilS a fluid capadtyof approl(lmatlefy 30 ml, while the subarachnoid space has a capacity of .app!'QlCimatlefy 120 mi. Not~: lfle three apertures (paired f~raf apertures (foramina of Luschka] irld an unpaired median aperture (foramen of Migendle)), through which Cl!n!brospfnaf tlufd flows from the deeperventrfcufar system Into the more supe!fldaf sub.'lrachnold space.

Putamen

\"ii:.:--:-- Hlppoampal ftmlxfa

It

c lmpai'Unt mur.tures nelghbor'lng tbe lltltraf wntrtdes ;a Vlewoflflebrilnfrom upper left. b VIew of the fr1ferfor hom of the left later
• The followfng brain structures border on the lateral ventricles: • The caudate nucleus (anterolateral wall of the interior horn) • The thalamus (po5tlerofateral\wff of the ar1terior hom}

• The put.amen, which~ fatleraf to the fat· C!l'af ventricle and don not border it di· ne<:tly. b The hippoampus (H't p. 206) i$ 1/isible in the anterior part of lfle floor of the !nfafor hom. ItS interior po!1Sons v.ith the hippocampal digit.ttiaru protrude int:D the ven· trfcularcavlty.

D utenlwallofthetfllrdwntrtde Midsag~l section, left lateral view. The lab!raf wall of the dlfrd ventrfcle ls formed by structures of the diencephalon (epltt!afamus, thalamus. hypothalamus}. Pro!I'UIIons of the thalami an both sicles may touch each ather (intec-lhalamlc adhesion) but are not functlonillly or inatamlcally a~nnected and thus do nat constitute a a~mmrssuraf tract.

193

NeurDGnatomy - - 3. Ventricular S}'stem and Cerebrospinal Ruld

3.2

Cerebrospinal Fluid, Circulation and Cisterns

Arochnold granulations

Choroid plexus of lateralventride

Choroid plexus of third vontride

int1!r- ---+---+-HT---+--,'--hemispheric cistern

straight sinus

lnll!r- --+------\1---\,----___,f-----,.-7---"'<---... ventrlaJiar

Cerebral aqueduct

foramen

tl"7''--+---- Confluence of the sinuses

l

l!lt"<:::+- +---""'"'""'SL-c......,L---- Choroid plexus of fourth vonb1cle

ChlasmaHc

Basal cistern

clstem

Cerebellomedullary dstem (cisterna magna)

lnterpedunaJiar clstem

1+---++t- - - Central canal

IN.F.--\--7"-:--- Vertebral VE'nOus plexus

Subarachnoid space

A Cerebrospinal fluid drmlatlon and the dstems Cerebrospinal fluid (CSF) Is produced In the choroid plexus, which Is present to some extent In each of the four cerebral ventricles_ It flows through the median aperture and paired lateral apertures (not shown; seeP- 192 for location) Into the subarachnoid space, which contains expansions called cisterns. Most of the CSF drains from the subarachnoid space through the arachnoid granulations, and smaller amounts drain along the proximal portions of the spinal nerves Into venous plexuses or

194

lymphatic pathways (see Fl- The cerebral ventricles and subarachnoid space have a combined capacity of approximately 150 ml ofCSF (20% In the ventricles and 80% In the subarachnoid space). This volume Is completely replaced two to four times dally, so that approximately 500 ml of CSF must be produced each day. Obstruction of CSF drainage will therefore cause a rise In Intracranial pressure (see E, P- 197)-

NeuJOGI'H1tomy - - 3. Ventrlallar .s)mm and C8'ebrosptnal Fluid

Postl!ffor Cllarold plelClls thalamic nudi!<.IS of1mn1 wntrldt

B Choroid plexus lrt 1M Iatini wntl'ldes

c Olonlld plexus lrt tfle l'ourtfl wntrklt

Re.llr view of the thalamus. Surrourlding brain tissue has bftn removed down to the floor of the liltl!r.ll vent:rfde:s. where tile choroid plexus Olfgtnates. The plexus ts adherertt to the ven· tritular w.~ll at only one sin! (see D) and an thus float freely In the ventricular system.

Posterior view of the p;Jrtially cpened rhom· bcld fossa (with the arebdlum rm~oved). Portions of the dlorold plexus ire ittached to the roof of tile fourth ventrtde <1rld run along the l~teral aperture. Free CS'Ids of the choroid plexus may extend thro~~gh tile latEral iper· t:ures Into the subarachnoid sp;~ce on bolh sides c·aochdalek's tlcwer baskl!t•).

Dur.~lwnous

Epenctpn;a - ---7-:-;'

sinus

I~Sf;.•Yi.l.._

D Taenlaeoftflechcroldplexus Superior view cf the ventricular system. The choroid plexus Is fonned by the Ingrowth of vasculir loops Into the ependyma, which tlrmly .rttach It to the wall of the associated ventricle (see F). Whe'l the plexus tinue is removed with a forceps, Its lines of attachment. ailed uenlae. car1 be seen.

Choi'CIId plelrus

OF~----~~~~~~

Medlin apertu~

=::::t\7=~~~~~- ~I'll

1queduct

Liter.!I wntrfclt

E Hllltclogkal sectt:on ofthedloroldpltii.Ut, wttfla detallst.vTng tfle strueblre oftfle pltii.Ut epltflellum (Jfter IC;Ihle) The choroid plexus Is a protrusion of the ventrfculirwall. It Is often Ilk· enedto a caullflowerbeCiluseoflts extenslllesurfacefolds. Theeplthe· lium of the choroid plexus consists of a single layer of a..boidal cells and has a brush bcrderon Its apical SIJ!face(to lncreasethesurf.K:eireafur· ther).

ltllnl wn1Jide

F Sc:IH!mltk dllgram of cerebrasplr11l fluid dl'tUIUort IU noted eiriier. the choroid plexus is prwent tv some extent in each of the four cerebril ventrfcles. It produces CSF, which flows through the two lateral .i!pert:ures (not shown) ind medl.iln aperture Into the sub-

arachnoid sp;~ce. From there. mcst of tile CSF drains through tile ar.achnokl gr.mulat!ons Into the dural va1ous sinuses.

~or

CI\I'Mdstlem

Olmmunk;;rtlng lrtl!ly

(endost$ the <Jntl!rlor

IIUddleoerebr.ll artery

dlol'llclalartery}

l),.,~~~crr--AmblentclsiB11(en· dosH po:ltlerfar anbral lrtl!ly and superior czrebellar artery)

Median ponlfne c1st1m

Antl!rfa r Inferior arebel far artery

Floaulus

Posl:2rfor

Ci SUbandlnoTd cTstemt (afb!r Rauber and

l(npsch) Basal view. The dstems <~re CSF·fllled exp;~n­ stons of the subar.achnofd space. They ccnuin the proxim~l portion$ of some cr;nial nerves arld baSil cerebral arterles (veins are not shown). When arterial bleeding octurs (as from a ruptured aneurysm), blood will slep into the SIJbarachnoid space and enter tile CSF. A ruptured Intracranial anUJrysm Is a frequent ause of blood In the CSF (methods of sampling the CSF .are desa!bed en p. 197).

SJllnaldlt2m

195

NeurDGnatomy - - 3. Ventricular S}'stem and Cerebrospinal Ruld

3.3

Circumventricular Organs and Tissue Barriers in the Brain

Yasrular o~an of lamina tennlnalls

Subfomical organ

A Location of the clrcurnventrlcular organs Midsagittal section, left lateral view. The circumventricular organs include the following:

~-';---- Subcommissun~l

organ

• • • •

Posterior pituitary with the neurohemal region (see p. 222) Choroid plexus (seep. 195) Pineal body (seep. 224) Vascular organ of the lamina terminalis, subfomical organ, subcommissural organ, and area postrema (see B).

The circumventricular or ependymal organs all have several features in common. They are composed of modified ependyma, they usually border on the ventricular and subarachnoid CSF spaces, and they are located in the median plane (except the choroid plexus. though it does drvrlop from an unpaired primordium in the median plane). The bloodbrain barrier is usually absent in these organs (see C and D; except the subcommissural organ).

Choroid plexus

Tuber clnereum

B Summary of the smaller clra.nnventrlwlar organs In addition to the four regions listed below. the circumventricular organs include the posterior pituitary. choroid plexus. and pineal body. The functional descriptions are based largely on experimental studies in animals. Organ

l.oCIItlon

function

V........,r

V;ncular loops in tile rostral wall of the third ventricle (lam· ina terminalis); rudimentary In humans

Secretes the regul;~tory

5ubfomlal organ(5FO)

Fenestrated capillilrles between the lnterventrlculilr for;omina and below thefomices

Secretes somatostatin and lullberin from nerve endlngs; contains eels sensltive to angiotensin II; plays a centr;ol role in the ~ulation of fluid balance ("o~an of thirst")

5uila)mmls· su..lorgan

Borders on the pineal body; overlies the epithalilmic commissure at the junction of the tllird ventricle and cell!bral aqueduct

Secretes glycoprotelnslnto the iqUeduct tllat condense to form the Reissnerfiber, which may extend into the central canal of the spinal cord; blood-brain barrier Is Intact; function Is not completely understood

Paired organs In the floor of the caudal end of the rhomboid fossa, richly vasOJiarized

Trigger zone for the emetic reflex (absence of tile blood-brain barrier); atrophies in humans after middeage

/~'lii\i---1-

Tuber clnereum

organofthe lamillil

...,.lnalls (VOLT)

(5CO)

Area postft.... (AP)

196

honnones somat:Dstatin.

luliberin, and motilin; contains eels sensitive to angiotensin II; Is a neuroendocrine mediator C Demonstr.tion of tissue barriers In the brain (after Kahle) a Blood-brain barrier, b blood-CSF barrier. The upper drawings show an Inferior view of a transverse section through a rabbit brain, and the lower drawings show tile brain stem from the basal aspect. The function of these barrlers Is to protect tile brain from hamnful substances In the bloodstream. These Include macromolecular as well as small molecular phamnaceutlcal compounds. a Demonstration of the blood-brain banter: The intravenous injection of trypan blue dye (first Goldmann test) stains almost all organs blue except the brain and spinal cord. Even the dura and choroid plexus show heavy blue staining. Faint blue staining is noted in the tuber cinereum (neurohemal region of the posterior pituitary), area postrema, and spinal ganglia (absence of tile blood-brain barrier in these regions). The same pattern of color distribution occurs naturally in jaundia?, where bile pigment stains all organs but the brain and spinal cord, analogous to trypan blue in the first Goldmann test. b Demonstration of the blood-CSF banter: When the dye is injected into the CSF{second Goldmann test), the brain and spinal cord (CNS) show diffuse superficial staining while tile rest of the body remains unstained. This shows that a barrier exists b~n the CSF and blood, but not between the CSF and tile CNS.

Neuroanatomy - - 3. Ventricular System and Cerebrospinal Fluid

D Blood-brain bilrrter and blood-CSF bilrrler

a Normal brain tissue with an Intact blood-brain barrier; b Blood-CSF barrier In the choroid plexus.

Vent~cularCSF

-m-0

Ependymala!ll - -

Broad lnll!rcellularspaO!S

a The blood-brain barrier in normal brain tissue consists mainly of the tight junctions between capillary endothelial cells. It prevents the paracellular diffusion of hydrophilic substances from CNS capillaries into surrounding tissues and in the opposite direction as well. Essential hydrophilic substances that are needed by CNS must be channeled through the barrier with the aid of specific transport mechanisms (e.g., glucose by an insulin-dependent transporter). b The blood-brain barrier is absent at fenestrated capillary endothelial cells in the choroid plexus and other circumventricular organs (see A), which allow substances to pass freely from the bloodstream Into the brain tissue and vice versa. Tight junctions In the overlying ependyma (choroid plexus epithelium) do, however, create a two-way barrier between the brain tissue and ventricular CSF In these regions. In other words, the diffusion barrier Is shifted from the vascular endothelium to the cells of tile ependyma and choroid plexus.

Brain tissue - - -

Tight junctions

Capillorylumen

a

Ventrla~larCSF

---

Choroid plexus-~ Tight junctions epithelialcell ~

Braintissue

- ~ :~=:~cell _j~ Caplllorylumen

b

F Comparison of cerebrospinal fluid and blood Hrum Infection of the brain and its coverings (meningitis), subarachnoid hemorrhage, and tumor metastases can all be diagnosed by CSF examination. As the table indicates, CSF is more than a simple ultrafiltrate of blood serum. Its primary function is to impart buoyancy of the brain (the brain has an effective weight of only about 50 g despite a mass of 1300g). Decreased CNS production therefore increases pressure on the spine and also renders the brain more susceptible to injury (less cushioning). CSF

b E Obtaining cerebrospinal fluid samples a Lumbar puncture: This Is the method ofchoice for sampling the CSF. A needle Is inserted precisely In the midline between the spinous processes of L3 and L4 and Is advanced Into the dural sac (lumbar cistern). At this time a fluid sample can be drawn and the CSF pressure can be measured for diagnostic purposes by connecting a manometer to the needle. Lumbar puncture Is contraindicated If the Intracranial pressure Is markedly Increased, as It may cause a precipitous cranial to spinal pressure gradient, causing tile bralnstem to herniate through the foramen magnum. This would exert pressure on vitally Important centers In the medulla oblongata, with a potentially fatal outcome. Thus, the physician should always check for signs of Increased Intracranial pressure (e.g., papilledema, seep. 133) before performing a lumbar puncture. b Subocdpital puncture: This technique should be used only In exceptlooal cases where a lumbar puncture Is contraindicated (e.g., by a spinal cord tumor), because It may, rarely, produce a fatal complication. The mortality risk results from the need to pass a needle through the cerebellomedullary cistern (cisterna magna), which may endanger vital centers In the medulla oblongata.

Serum

Pressure

50-180mm HP

Volume

100-160ml

Osmol..tty

292-297 mOsm/L

285-295 mOsm/L

EledrolytH Sodium Potassium Calcium Chlor1de

137-145mM 2.7-3.9mM 1-1.5mM 116-122 mM

136-145mM 3.5-S.OmM 2.2-2.6mM 98-106mM

pH

7.31-7.34

7.38-7.44

Glucose

2.2-3.9mM

4.2-6.4mM

CSF/serum gluco..,ratio

> 0.5-0.6

Lactate

1-2mM

0.6-1.7 mM

TDhlprotSI Albumin lgG

0.2-0.Sg/L 56-751 0.01-0.014 g/L

55-80g/L 50-601 8-15g/L

r.-lmnboo

< 4cels/!ll

cymphocytes

60-701

197

Telencephalon, Development and External Structure

4.1

Neo-

An:tll-

pallium

palr.Jm

Neo-

pallium

Vtnt!fde

OcdplbV

audal

Corpus strial\lm

I>.Jieo-

•

A Tcnnnfloutlounddlredlon Mld~glttal section ¥1ewed from the left side. Terms of locitlon and dl· rec:tlor11n the tl!lencephalofl and diencephalon are based on the Fore! axis (2), which nms horizontally through the forebrain. (1) Br.ainstl!m a:ds (Meynert axis).

Piflhrn

Corpus strial\lm

b

8 Dewlopmantofthecerelnlcurtax Embryonic br<~ln: b adult br<~ln. Tbe cerebral hemispheres can be dhllded Into phylogenetlcally 01nc1ent ("paleo"), old ("archi") and new ("neo•) pam (see D). The cerebral co~ tv: together with aJ3oclilted ilreti of unclerfylng white miltter Is called the pallium. 01term sometimes used lnterchangablywlth "cori2X".

;a

Plllfeul

cpen:ulum

b c Cinry and white mlttl!r In tfle teleMII!phllan

a Coronal sectior\ showing the distribution of gray and white mattA!r in thebr<~ln.

Cny mlltter:

• Cerebral cortex: contains mon ofthe graymiltter ofthetelencephalon.lt Is dlllkled on histological grounds Into two parts: - Isocortex: corresponds to the neocortex (see 8): largest part of the cerebral cortex. consisting of siX layers (seep. 200). - Allocortex: corresponds tD the paleo· and archit:orteus (see 8); consists of th~ or {our layers (see p. 204).

• Subcortical nuclei: Ba!
h-.

198

lnsularlcbe

Tempor.~l

(•ll\'l\lla}

opeu~klm

• Other gray-matter nudel that are not lr1Ciuded among the bas.~l

901nlgia of the telefiCephalan: - Amygdala: often considered a trafiSitiOnal form between the two types of gray mattC!I'-cortex and bawl gangli;a-based on Its location (seep. 207) - Oaustrum Wblll! llliiUI!t': !issue below the cerebral cortex <1nd suiT'Oundlng the 5Ubccrtlcal nudel. Nolle; The white matl:l!r also cuntalns nuclei of the diena!phalon (seep. 215). b Literal view of the left hemisphere. Part of the cerebral cortex sinks below the surf.rce during development. forming the Insula. The portions of the cerebral cortex that cwerlle deeper curtlcal ai'NS are called opercula ("little lids").

NeuJOGrurtomy - - 4. TeiMOI!pllalon(Cm!bnlm)

D Pf¥osenettc origins of m.1}or compomentl of the telencephillofl

l'hvlotllntCic1Bm

Slruellft Ill the

_.,..nk.,...

snc&ul'l(s) ~ the ..ult ....~

CerttaiiCIUctuN

Paleopallium (oldest part)

Floor ofthe hemispheres

• Rhinencephalon (- alfadllry bulb plus surrounding region)

AIIOCDrtelc (see p.204)

Medial pcwtlon of hemispheric

o Ammon's horn O.argest part. not shown her.) • Indusium grlsalm • Fornbt

AIIOCDrte!c

• Neoconex(-conex),largestpartofthe ce.-,ral
l~nex(see p, ZOO)

~hlpalhum (old part)

wall

Neopalhum (newest part)

Most of the brain su~Rce plus the deeper
Umble

forrix

Temporal lobe

Ocd'pltll

lobe

E DlvbTonoftftecerebnll hem..ph-1.- lobes Left laterill vfewofthe left hemisphere: b Left lat:mlvlewoftlle rtght hemisphere; c Basal view With the briln51Jem removed, showing the cut surfaa! of the midbrain (mesencephalon). The two cerebral hemispheres ~re the externally visible part of the telellcephalon. They ire separated from each other by the longitudinal cerebr.ill tlS;Sure .and are each subdiYided 1111» siX lobes:

;a

• • • • • •

Frontilllobe P.ilrfetilllobe Tempor~llobe

Occipital lobe Insular lobe (Insula, see 0,) Limbic lobe (limbus)

The sulface contours Glthe cerebral hemlsphen!s are hlghlyvartable betwl!en individuals. A hirtDiagical subdillisian in1» cortical areas is more meaningful lfl terms of fufiCt!ONI briln organlz:atfor1 thar1 a macroscopic subdivision 1111» gyri irld sulci (seep. 200).

199

4.2

Cerebral Cortex, Histological Strodure and Functional Organization

A Hlstologlul stnJdure oftile Gl!ft!bl'llll corti!X

A six-layered (laminar) structure b found throughout most of the neo· colUX. The slhlef Impregnation (a) or Nlssl staining oftfte cell bodies (b) allows for hlstologlt.ll diVIsion of Ute -rtex according to Ute doml· nant structure of each layer: II Ill IV V VI

Molecular la'yer: (outennost layer); relatively few ne~.~rons. Extemal granular layer: mostly ~!late and sc.rtn!red small pyra· mldill neurons. Extl!mal pyramidal layer: small pyrilmldal neurons. lnb!rnal granular layer: stellatz an small pyr.amidal neurons. lnwrnal pyramidal layer: large pyramidal neurons. Mu!Ufonm layer. (lnnennost layer}: neurons of v<~rfed shape and slzl!.

Cortlt.ll areas that are concerned prfmarllyYoith Information proce~lng (e.g .• primary somatosensory cortex) are rtch In granule ~Is; Ute granularlayen of these regions (gf!1f!t.llor-. see Ba)arealso exception· ally thlc:k. Areas In which Information Is tr
•

b

B Exolmples ofgranuln 01rtd "'JI'illllllilrcortl!ll.

a Granular cortex (koniacortex from tne Greek kanis • sand): The p(omarysom
tennlnate (at layerIV). Is locited In Ute postcentrill gyrus.ltls thinner overall than !he primary somatomotor cortex (see b). Astriking fea· ture in the primary somatosensory cortex is that tne external and lntemal granular layers (II and IV) where the large sensory tracts terminate are rnarfcedly widened. By contr<~st. the pyramidal cell layers {Ill and V) are thinned. b A9ranular a~rtex: The effi!rents fibers that pmject to the motor nudei of the cranial nerves and !Mtor columns of the spinal cord origlnatt' In Ute primary somatomotor ca~UX.Ioc:ated In Ute precentr;al gyrus. ItS pyramidal layers {Ill .and V) .are greatly enlarged. Exceptionally large pyr~midal neurons (Betz cells afb!!r the ~uthor who first d~ scribed them) ;rre found In the some areas oflayerV. Their long
200

Neuroancrtvmy -

4.. TelencephGion (Cerebnlm}

Q:oebral (l)rte!< {neoan1a}

}

}I }n -.ron

}Ill

Sl
}1v

Lorge pyr.~mklll

)v

S11111l Pr111mldll

nBiran

l.IY'f

}· 1'111111

a

b

c

C COiumrwr ort~nlatlon of the COI'tU (after Klinlct ~ nd SilbernagI} While morphologlal con,demlons divide the cereb1111l cortex Into hortzontallayers (su A), functiON I conslder.Jtlons lead to Its dMslon Into distinct unlb or modules (see C). Encompnsing illl sod~. thex modules consist of ¥ertlally-mm9td mrtkol Clllwnns of neurons that are lnt2rconnected ;~ serve a common function, despite showing no distinct hlstologltlll boundutes. In total. there are snen~l mWion such modules In the c:el'tbrilll cort.x, with il wmble width between 50 ilnd SOO pm NCh. One cortical column has here been n\llgnified to display lb mnstill.lent neurons 1nd connKtlons In sepum panels. Pilnels ...c ihowthe principal typlli of celk parlfc:l~ng In ,. cortlal column: s~Mnl thouHnd Jkllo~ nlll/f'Df1S of various subtype and one hundred or so luge 1nd sm1ll pyn~mldill neurons (p1nel 1). Pilnellllsoliltes the sn\1111 pyr.~midal cells whose alll)l\$ tend to terminate within the cortex

d

e

ibelf. In contrast. the deeper, large pyn~midal neurons (panel c) IIM:amns that genen~lly project to suboortlcal structures. Large pyn~mldill cells ilre responsible for tracts of cortkobulbir ;~nd mrtlcmpiNI motor :amns.which projectto the brillnstem 1ndsplnill curd, respectively.They may also send recurrent collarill ftben which end In theloal corta Panels d-f mnbln aans projecllng lhlll the e«ebr.al cortex. Panel d lsoliltes thillirnowrtlal projections that mt2r from the th~1mus iind synapse mostly on the stelliiW neurons of layer IV. Incoming 1ssod~on fibers of the nearby cortex and commissural fibers of the contralateral hemisphere frequendy termlrute on the dendrites of the sn\1111 pyramldill neurons (panel e}. Panel f shows the llrge Wllmldal neurons whose apical dendrites reach from layer V to layer I. These lilrge p)'lilmidal neurons Integrate Inputs from various other loa I neurons ilnd Incoming fibers.

D 1\'Pf!llll neuron In the cerebnl COI'tU (simplified)

Smlllt:e neuron (layers II and IV)

Cef I with short amn for loallnfonnllllon piDCJ!SIIng; various types: buRt. andetabra, double-bouquet c:efls

In hlbltory lnte
primary lnfonn•tlorrpi'OCieSSlng neuron (In llycr II),IS(McU!IIyln pr!INry SIIISOty I 111M

Smoll J¥amldill Milton (ilycrlll)

!All with lang uan !hot lllb!n ends wf1hln the carll!x, efttler ;os: • Association fiber. a:~n ends In silme hemisphere but d'rfr.rent corlialaru, or as • Commlaural fiber: uan ends In opposlm hemisphere but cattal aret ttl similar fvndlon

Large pyramldill n1uron

!Allwith wry lang ilCDI1 that proJects outside the corta. sometimes n!achlng distil ntslnld:ures

oubl• tt. c:artall

Cener1c 11trm tlor sm~ll neuron, most oft!!nwlth stellitJt morphology

Otpends on the cell type (we entries tlor stellilbt and small pyramidal neurons)

(Jay.rV)

Granule cell

(J¥rs • and IV)

Projection rwuron whOR nons end within the

co!WI

E'la:lbtllry proJ-dlon 11111 ron whose ...,ns•d

201

4.3

Neocortex, Cortical Areas

-~"""~.----- 1>.1~1

sulcus

Certr.JI sulcur.

3

1

2

\ II

• 202

NeuJOGrurtomy - - 4. TeiMOI!pllalon(Cm!bnlm)

A Brodrn~nnareBrntfle~ a Midsagittal section of the right arebr.al hemisphere,. viewed from the left side; b Later~l Ylew ofthe leftcerebr~l hemisphere. As noted earlier, the surfaa of the brain conslm mila05coplcally of

lobes, gyri, and sulci. Microscopically, however, subtle dlffere11ces an be found in the dirtributiorl of the cortical ne.Jrons, and some of these differences do n~t conform to the gross surface anatomy of the brain. Portions ofthe «rebral correxthat have !he same bil!lc microscopic feallJresare called coti:Sarl atl!QsorcommltJelds. This organ!Dtlon Into cortical ~re;~~~ is b;~~~ed on the distribution ~f neurons in the different layers of the cortex (cytooldtllmonlcr, see A. p. 200). In the brain map shown at left, these areas are Indicated by different colors. Allttough the size of the cortical areas may vary between lndMduals, the brain map pictured here is still used toci;Jy as a standa~ re~rence chart. It Wis developed

In !he ~riy 20th century by the .anatomist Korblnlan Brodmann (186&1918), wn~ spent years painstalcingly examining the ~:ellular architectiJre of the cortex In a single brain. It has long been thought that the map created by Brodmann accurately reflects the functional organlza. t1on ofthe cortex.. and Indeed, modern Imaging techniques have shown !flat many of the cytologically defined areas are associmd witfl specific functions. There Is no n~. of course. to memorlre the loc.TI!on of all the cortical areis, but the following <~reas are of special Interest • Areas 1, 2. and l: primary somatosensory cortex • Areol4 primary motor cortex • Areol 17: primary visual cortex (strim area, the exb!nt of which i$ best ~ppreclated In the midsilgittal section) • Areols41 and42:audltorycortex

Planeof!il!
lnb

b

8 Vftull cortex (strTituret)

Rlghthemlspherevlewedf'romthelefl:slde: b Coronalsectlon{plane ohectlon shown Ina), anterlorvlew. The ptimary'llisual mrtex (striab! are
;a

an unstained coronal section (b), the st11a o{Gennad can be Identified;~~~ a promlnem white s!Jfpe within the gri}' cortical area. This stripe contains cortical association ftben that synapse With the neurons of the lntemal gr.anular layer (IV, see p. 201). The pyramidal all layers (effen!nt flbers) are <~ttenNted In the visual cortex. while the gr~nular ceU layers where the afferart:flbers from the lateral geniculate nudws temniNte are markl!dly enlarged.

203

4.4

Allocortex, Overview

A OW!rvlll!w of thullocortu:

v- of the base of the br~in (a) ~nd the median surf.lce of the right hemlsphere(b). Structures belonging to the illocol1eKirt' lndlc:.rted by colored shading (see listing of allocorttcal structutel in D, p. 199). The illocortexcomlsts of the p~enet!cally old Pitt of the c:erebril co lUX. It Is very smill In reladon to the co lUX as a 1Miole.. Unlike the isocortex. which hils a six-layered roucture, the allocorti!X (o/lo- "other") usually conslsb of three layers that encompi!ss the paleo- and archlcortel(es. Addldonally. there eXIst (olll'layered transition~! areas betwftn the allocorti!X ind lsocorti!X: the perlpaleocorteK (not Indicated separitely In the drawing) and the p1!11archfcorti!X (lndlc:.rted by pink snadlfl!l). An import!nt Pitt of the allocortex is the tftinmaphalort ("olf.lctory br.~ln"). Olf.rc:tory lm· pulses that are perceived by the olf.lc:tory bulb are the only sensory afferent Impulses that do not reach the cerebr;al e~:~rtex by way of the doml thalamus. Another Important part of the allocortExIs the hlppoampus and Its as~ datli!d nuclei (see p. 206). As In the Isocortex, the gyral patterns of the allocortex do not al· ~conform to Its histological orginlzatlon.

'!--+.~..-:::'::~~~--

Olfactory tract

~;~~v---~~~~---~~~

carla

..,...-.:=-::-::iri'-......- - - 1'8iirc:hlaJrla 1'--¥-___;~b:!!--

Atd!l.· c:arta

•

b

C4lpl.s

callosum

lndl.lll~.m

grtseun

B Orglnllatlan ot the 1rdllpallklrn: deeper parts ~ter;al viewofthe left hemisphere. The archilllrtexdescribed inA is the

on(y part of the archipallium that Is loated on the brain surf.rce. The

deeper parts of the irthlpi!lllum, which lie wtthfn the wltlt21TliUer, are the hlppocam~ ("sea horse"), Indusium grtseum ("gray covering"}, and fornix("arth"). All three structures;are part of the limbicsymm (see p. 374). ind together form .. border c·umbus") iround the corpus callosum as a result of their migration durfng development.

204

Neuroancrtvmy -

4.. Telencepholon (Ctnbnlm}

Lotl!r;ollanglllldl....l sll1o

Lo-.."'-,.,...---- lndtalwn ¢wum

Cllnu ofmrpus uiGlum

Splonumof CDrpul

Cn.a af I'Dmlx

C Topog~phyoftt. fvmlx. corpu1 calbum, 1nd upturn peludalm (~er falels) Oa:ipital Yitw frvm upper left. The fornix is a tnct of the archicortex thit Is closely ipposed but functlonilly unrelated to the corpus allosum. lhe corpus allosum Is th largest neocort1cal commissural tract betwftn the hemispheres, serving I:D Interconnect: cortical areas ohlmllirfunctlon In the two hemlspheru (see iilso p.376). The septum pel-

ulasum

'll>l!nlaoffon'bt

luddum Is a thin plite thit stretxheJ between the corpus callosum ilnd forniX, fosmlng the medial boundary of the lateral ventr1cles. Between the two ~ is a cavity of variable size, the aM/m npti pfllucidi. The d!ollnerglc nuclei In the septil, which are lnvoiYed In the organlziil:lon of memCHY, are connected to the hlppoampus bv the forniX (see p. 206).

Body arramlK

: . . ...~-------+--- W.ll'olll'llrlc:le. oa:lpltol ham

Crusof ----~--~--~~~~~~

fomlx

Cdumn

offon'bt

D Topognphyofthl hippocampus, famlx. iinll CJ1111USGI11511m VIewed frvm the upptr left iind Mal iiSpect. This drawing .shows the hippocampus on the floor of the lnfaior horn C1l the l
;,.....___::'----~--+---

laenll offGmlK

>--___;lpo';___ _ Lotl!rolwntrlde.

ll!mparll hom

miltter trut connectlng the hlppOCiimpus to the mammdlary bodies In the dlenaphiilon. C:OntalnedWithlnthefornlure hlppoamJNI neuRII'Is ~ illiDI!S project I:D the septum, mammdlary bodies. contralural hlppoamous, and other structure. This lmpomnt pathwiiy Is part of the Smbic.!ySiem (seep. 374).

205

4.5

Allocortex: Hippocampus and Amygdala

Corpus _ _T"'"".....,.=--':::~allosLm

~-f.....::'t-~~--::.--lh---

lndl.lllum g'lleilm

--~~~~~~~~~~--Rm~aM Nppoampus

Mammflary body

A left hJppoCimp.al l'annaUon L;atet;al view. Most of the left hemisphere hi!$ been ct~d ~.1_.­ lng onlytfu~ corpus c:.1llosum. fornix. and hlppoc:.1mpus. The lnt.1ct rfght

hemisphere lslllslble In the background. The hippocampal fDrmation is an important component of the limbic ')'$IW7I (seep. 374).1t consists of tnlft p;~rts: • Subit\llum($C!1C!Cb) • Hlppocimpus proper (Ammon's hom) • Dent.rte gyrus (fascia dent.tta}

I lllghthlppocamp;llforrmtfon andtheaud;rl partaftflefombl: IJ!ft: medial view. Comp;~ne this rnedlallllewofthe rfght hlppocamp;~l for· m.atiOnW!ththelatl!rallllewlnA.ilbove.AusefiJIIandmartc~theCAIIcartne

206

The tlber tract oftbe fornix connecu the hlppocamp!a to the mammlll;ary body. The hippoc:.1mpus integrates infol1niltion from various brain <1reas and Influences endocrfme, visceral, and emotional processes vla Its efferent output. ItIs p;~rtlculary associated with the e5t.1bllshrnentof short·tl!rm memory. Lesions of the hippocampus an therefor!! cause specific defects In memory formation. Besides the hlppoc:.1mpus. whkh Is the large-st part of the ardllcortex, we can recognize .ilnother component of the .archlcorti!X. the Indusium griseum.

sukus. which leadstothe ocdplt.al pole. The cortlc.ill are.astnat border the hlpp0c:.1mpus (e.g., the p;~rahlppocamp;~l gyrus) are partlculary apparent In thlsvlew.

Neuroamrfumy - - 4. Teknaphalon (c..brumJ

Dontat
""\..-........'>L-- !ilblcu..m

Plr• hippocampal

Enlatll11111

gyrus

~glon

Rmbrtl d

hippocampi&

~=-

Hlppoampol

si.IOA DoontR -r----;i~$,-.J.gynll

----------._..,

FlmbriiCII' hlppac~mpus

Flrnbrii of

hlppoampw

Hlppocompw

=.:"'" HlpPDColmPI&

•

..

Enbxt11nol "'!!IDn

C LefttemponiiDbewTdl the Wertor hom of the leten~lwntrtde apMed

• ll'anS¥8lle section, pom.rtar Ylew of the hlppoampus on the floor of the lnNrfor (tempor.l) hom. The following stl'\lctures can be ldtntlfted from lilteral Ill medial: hippocampus, fimbria. dentate QYfU$, hippoCiimpal sulcus, and p;anhlppoc.llmpal gyrus. b Coron~l sedlons of the left: hlppoCiimpus. The hippocampus appears here as a curled INnd (Ammon's hom • the hlppOCiimpus proper), whic:h shows considerable structural diVI!f51ty In Its different portions. The junction between the entorhinal cortex (entomlnal region) In tht pariihlppocampal gyrus Qnd Ammon's hom is formed by a tr1ns1Uonalarta, the subiculum. The entorhinal region Is the •gateway• to the hi~>­ poCimplll, through which the hippocampus re.:eilles most of its afferent fibers•

Lmrll nucleus

.. D lleladDIIIhlp afdlumvgd..l tD 'nbmll brilln ltnlduN Lateral view of the lllf't hemisphere. The amygdala (amygdaloid body) Is loated below the putamen and anterior to the tall ofthe uudm nucleus. The fibers of the pyramidal tract run posmrlor and medial to the amygdala.

E Alr'lyg&lll il

Coronalsectfon at the level of the lnte~n­ b1cu Ia r foramen. The amygda Ia extends medially to the Inferior surface of the cortex of the temporal lobe. For this reason, It Is considered to be part of the cortex as well as a nudear complex that has mlgntl!d Into the white mattEr. Stimulation of the amygdala In humans leads Ill changes In mood, nnglng from nge and rear to rest and relaatlon depending on the emotional state of the patient lmmedliltely prior to stimulation. Since the amygdala functions as iln "emotional amplifier; lesions ilffect the patient's evaluation of I!Y81I3' emotiOililf slgnlflunce. The su nou ndlng periiimygdallne cortex iincl the mrtfcomedl~ hiIfofthe amygdal• are put of the primary

11<1111 nudtus, lltnlpert

C:Ortlal nucleus

l
olfactory (])rl1-.x. Hence these portions of the amygd1l1 are considered part of the paleocortex, while the deeper portion Is dharacterized as "nucle~r.• b Detail from 1 showing the two main groups of nudelln the amygdo1lo1: • Phytogenetk:illy old mrtfcomedla I group: - CortiCII nucleus - Central nucllllus • Phytogenetk:illy new 1Nsolatero1l group: - Bwlnudeus - Literal nucleus

The INsal nudeus e~n be subdivided Into a parvocellulir medial part 111d a macrDallular literal part.

207

4.6

Telencephalon: White Matter and Basal Ganglia

~.-.----------!"'-:!!:--

SUper!orlongltudlnal f'al:clalus

A Tee sed ftbu p....,.uon ofthewh~ lllltterclthe tl!leiiCII!flhllon

Lateral view of the left hemisphere. This dim!ction shclw$ the wper· f!clallayer of whlre mat:tef loc.rted bet:wHn the basal ganglia and the gray mat:tef of the cerebril COI1:eX. A spedil prep;u'itlon technique WiS used m display the ftber structure of the whlre matter, which normally has a unlform white appwance. The fibEr structure b defined by the ttilc:t3 (bundles of myelinated illCIOns)thilt Interconnect different areas of the gray mit:te!'. For example, we Cirl Identify the short cerebral arcuate

ftbers (U flben) that rul'l betweer1 two .adja.cent gyri as well as the association fibers thatsp;an multiple gyri (e.g., the wpc!rior longitlldinal and frontotemporill fasclcul~. WhE!l these 1r.1ets ilre dam.1ged (lr1 multiple sderosls, for example) the communication pathways wtthln the br.~ln ce.ase to function norm.ally. This may lead m centr.al p;mlysls, lltsual dlsturbancn (optic nerYe d;lmage), and behavioral cbanges (d;lmi!lge w the frontal cortex).

;----~-- T11lof caulilte nudeur.

B ProfKUon oftbe b.uil ganglia ontD the br<~tn wrfac:nnd

wntrtc:ullr system a Viewftomtheupperlefhnterioraspect. Thebasalgangliaaremaues of gr.~y matter deep within the brillrl that contain the cell bodies of neurons. Further details on the bilSal gar~glla are shown In c.

208

b Leftlata'aiYiew. Thecau~r~uc:lemlsdoselyapplledml:hecontiiVt' laterill wall of the lateral ventrfde.lt Is connected m the putimer1 by numerous sti'e111k·II!Ge b.'!!'Ids of gray mat:tef (corp~ Strfatl.lm, see C).

Neuroamrfumy - - 4. Teknaphalon (c..brumJ

}= Tall of -....:.,..~....:,...~::~o..,,;.....;. oaudatlo nude~a

c a.•.. ••nan•

• TranSYel1e section through the cerebrum a the level 1'1 the corpus strliltum (see D), viewed from above. In 1 strict anatDmlnl sense, the bllsal ganglia consist of the c;n... datE nucleus, putamen, and globus pillrdus. Develapmentally, the globoJs pallidus is a part of the dlenczphalon (see D, p. 211) that has migrated rnm the bl!lenUJJhalon, but it Is still counted among the basal gangIIa. 1he bllsal ganglia are ~n eswntloll component of the exnpyramldal motor sysmm (Its functional significance Is described on p. 340). 1he diustrum ("barrier") Is 1 strip of grily mltbr lmraltD the pwmen. It Is not part 1'1 the 1Ysal91ngU1 but lnsteid has redp~ Qll connections with sensory arus of the c:enbriil cortex. It Conlnill section through the cerebrum at the IM of the olfadDiy trilct. ilnterfor Ylew. This section dernonslrlbts how the caudabl! nudeuund putamen •~ separatEd from eildl odl• by the ftbrous white matter vf tfle Intern~ I capsule. The uudabl! nucleus and putamentzlgttber co"'utubl!the COIPUS slrfatum (often shortened to "strlatum": see D). The globus pallldus Is not lllslble bea use It Is ocdpltill to tflls plane Df section.

•

C.INI...

....._. / Clarpoa

.............

nud. .

-· ....... cow.

.............

/

........

Llnltrarnl

D llcr.tllllllhlp b~n the wrpu•lltrimlm •nd lentlfunn nud... The caudate nucleus and putamen together constitute the corpus strl· atum. while the publmen and globus pallldus makie up the lentlfomt c•Jens-sha ped") nucleus. Although the glooos pa llldus and the putamen

are anatomically juxtaposed, the publmen Is functionally assod1ted Instead with the caudate nucleus. Dewklpmentally, the putamen Is part of the Ulencephoi ion lind the globus paiUdus Is part of tfle diencephalon.

209

Neuroai'H1tomy - - 5. Dlfltcepholon

5.1

Diencephalon, Overview and Development

Hypothalamic SIJicu. (ventrald~tc sl.fcus)

Rlmbt lnt2r1flala1Tlc Ante!icr camiTisal.ft

adheslcn

SIJfa medullllr1s thalami

PreoptiC:

ansa

l'fneal

(ep~ls)

~alam1.11

SUpraopllc ~«:$$

ln!UKibl.far n!<:e5

Ante!iar~ofpllllttarygland

(adenahypaphysrs)

Mimmlllary body

Cen!bnl

T~nbJm

peduncle Mtsena!ph;llan

A The dlcnceph1hm lr1sltu Mld~gll:t11 sectlor1 of !he right hemisphere Ylewed from !he medial side. The dJencepbalon Is located below the corpus callosum. p.;~rt ofthe tzlencephalon, and abtwe the mesencephalon (midbrain). The lmral w.rll of the third ventricle. \llslble here. farms !he medial boundary of the dlencephillan. The tltalomus makes up four.ftftlts of!he enUre dlen· cephalon, but the only parts ofthe diencephalon that can be seer1 extef· nally are the hypothillamus (visible from the b;aal aspect) and portions of the epltltalamtiS (plne;rl, ¥1slble from the occlplt;rl aspect). The differ· enUatlon of these structures from the embryonic dlencepbalan Is shown

210

In D.
Toleraphallt -ld~

DlontiCihlllc

-de --l~----lr- Dltnaphalon

--phalli:

Toll

fmldbrat>)

- + - - Tda~a~>holon

dloroldei

wslde Rhamlloncophollc

•

.....de

Corpus allosum

Chordd plHUI Tolod""""'hollc

~~------~~~

bcundlry

choroldea

Portion af --+:r-\it>'!

Forni<

dlonmphllon wlslble Itthe

Third --=--=--- - --to]

base ofthe ~In

wnb1de

~=mllary (dloncophalan)

I Denlapmlntofthe lll~ne~pMian from thecl'ilnlill rwul'illtube Al'lt2rior vi-. To undem:and the location and extent of the diencephalon In ltle adult brlln,lt Is necess1ry tD know how It develops from ltle neural wbe. The dienc:ephalon and telencephalon both develop from lt!e prosence.,Nion, or telenc:eph•llc vesicle (see p. 183). As development proceeds, ltle two hemisphms of the telencephalic vesicle (red) eJCpilnd, OYergrowlng ltle dlence.,NIIc veslde (blue). ThIs process shifts the boundary beboeen the telenaphalon and diencephalon until only il small am of lt!e diencephalon Ciln be seen at the base of the adult brain(-A).

C l'astieliar ll!lodiHCIIphlllc llounll•ry CDronal sections. Embrvvnlc bnlln. The development of the telencephalon (red) has progressed consldenbly In relation lio B. The lmn~l venb1cles containing the d!oroid plexus hilve almdy completely overgrown ltle di· enceph•lon (blue) from bettlnd. The medial wall of lt!e lllteral venllf· des is very thin md has not ~t fused to 1he dia~ceph•lon. Bm¥ftn lt!e tElencephalon and diencephalon Is 1 wscul•rlz:ed sheet of connec!M tissue. the t6l choroidn. 11 Adult bnlra. By the ilidult suge, ltle tela choroldea ilnd the medlill wall of the ~tenl ventride h41W! become fused lio the diencephalon. Removing lt!e choroid plexus 1 nd the thin tJ!Iil dloroldN ilfrords a direct lliew of 1he p05b!romedlal boundary of the diencephalon p.2121.

il

c-a.

~~-+-~-E~~~A tflalamus

Th1lamus (dorsa~

-+--_......,,__

Sub- - - - - ' ; - - - tflolamus

Globus poolllcb

D ClrgllniZIIIIIIII aftlle dlenarphlllan durtng embryDnlc development CDronal section of an embryonic bl"llln (left) and an adult brain (right) demonstraUng the parts af the diencephalon. Because the dla~cephalon ofthe adult brain lies between the tela~ceph­ a Ion and mesence.,Nion, the l!cendlng and descending OIXDns must penetr.lte this part of the brain during d~Mioprnent, fvrmlng 1he IntErnal capsule. As development proceeds, ttle OIXDn bundles thiltfonn ltle lntennal capsule migrate through the subthalamus (black arrows), displacing the gremr porUon of It bl:a!'lllly. ThIs laterally displaced part of the subthalamus Is called the globus pa/Rdus. Although the globus pallldus Is displaced anatornlally Into the telll'lc:ephalon and Is considered part of the telencephalon In a topographk:ll sense, It still retains d05e functional ties with the subthalamus, IS bolt! are part of lt!e I!Xtrapyramldal motor system. The rnrdlo/ part of the subthalamus reiTiillns In the diencephalon as the t7w sublilalatnus (not vlslble In this plane of section). As a result. the lnb!mal capsule ofthe telencephalon fvnns the litEral boundary of the diencephalon. The dllhrent parts of the diencephalon grow to re~~d! different definitive s.l.lies. The thalamus g~ dlsproporllonmly and -ntulllyocCIIples four-fifths of the miture diencephalon.

211

-~

~ Tlllrd

CU!edgeol

wntrfde

lmralwntrfde

Taenia ct!onllclt.a

Anl8ior tl.lb«cle Optic

Habenula

tract

Infundibulum

Oculcmclor

·~

Pineal

Mcdill

l~'llelluncu~r

Qrebr.Jif)edunde

llelllall;~te

lo$sa

boctt

P\IMnar ~I

gentoJ!ne

boctt

III---+H-- - - - - MediJ~ ablangm

• genlaJiate body Is an Important relay station lr1 the visual pathway, just a~ tile medial genla!late body Is ar~lmpottlnt relay station In the .auditory p;~thway. BoCh are counted <~mong tile tftalamlc nuclei, and together they constitute the mo!llll:llalamus, an exlznsion of the thalamus proper. The pulvlr~ar ("pillow"), which encompiiSses the posterior thalamic nuclei, Is seen particularly well In this section.

C The dlenceph;~lon <~nd bratnstem

• Anterior view, b lonremoved.

postl!tiorvlew~thtftecerebellum andtl!lencepha·

a The optic tract marks the lateral boundary of Ute diencephalon. It winds arDund the arebral pedundes (crura cen!bti), which are p;~rt of the adjacent midbrain (mesencephalon). b The epithalamus. which Is formed by Ute pineal and the two habe· nulae (•relru"), 1~ well displayed 1r1 this pomrlor view. The latl!r.ill

lntuutbl.fum

Gerebr.alpedunde - -l'--iiii='--SubstM1tla --~­

nigra fl;!d

nucleus

Gefelnl

aqueduct

D 1.oa1t1an oftfle dlencephiiDn In tile 1dult bnln Bi1Sal11iew ofthe brain (the br.llnstem has Ileal sectioned at the level of the mesencephalon). The structures that carl be lderniHed lr1 tftls view represent Ute parts of the diencephalon sltu.iltl!d on the bas.al surface of the brain. This view also demonstrates how the optic b'act. which it. p;~rt of the diencephalon. wlrlds arourld the cen!br.ll peduncles of themesencephalorl (see Ctt). Due to the expansion oftfte telencephalon, only a few structures of Ute diencephalon car1 be seen or1 Ute undersurface of the brain: • • • • • • • •

Optic netve Optic chliiSm Optlctract Tuber clnereum wllh the Infundibulum Mammillary bodies Medial geniculate bel ely (see Cb) lateral genial late body Posterior lobe of the pltultlry gland (neurDhypophysls, seep. 222)

213

Neuroai'H1tomy - - 5. Dlfltcepholon

5.3

Diencephalon, Internal Structure

8a

IIJ lk

'--------1~~~~~~-----~~r

clnM!&.m I'Dnesofstdlon 'hi

A lbefourp;ntsoftfledlencephilon llllu..-,1•

FundiDn

Regulatfon of drudlan mythms; Rnlclng ofolfactory

• PlnNI gland • Habenulae

¥lam liD bralnstem

• Thalamus

Relay af sen.ory lnfonnatlo"' .asslmnmln regulation of mollorfunctlon

• Subthalamk nucleus • Zonainaru

Relay af smsory lnfonnatlon (somablmotor zone of diencephalon)

• Globus pallldus (see E, p. 225)

• OptiC dllasm. opUc tract • Tub.-dnereum. neurohypophysis

Coordlnaaon af aublnomlc nerwus ¥lam wl1h enG> cline ¥lam; participation In visual pathway

• Mammillary bodies • This Is lhe only sula&S sh-n In A.

I Canlrlill seatons thnlllgh tfle dll!f'IOI!tlb;llan ilt tfll'ft dlll1!rent levels a 1.2wl of tfle aplk: diT11m: Portians of the diena!phal~:~n and tel· encq~halon appt'ar In thls section, which dearly s t - the posl· tlon of the diencephalon or1 both sides of the tillrd wmrlde. All out· pouching ofthethlrdventrfcle, the preoptic recess, Is located ib<M! the ~:~ptic miasm. Its mnrM!Ction ID the third venbicle lies outside this plane ofsectlor1. b 1.2wl of the tuber c11unum, just behind the lnte!ventrlcular foramen: The boundary betweer1 the drencephiiOflind tl!lencephalon Is de;~riy defined only in the regior1 abgut tfle VC!IltridH; tfle underly-

214

lng nuclear areas blend together with no ipp<~rent boundary. Alor~g the litl!ril ventricles, the boundary between the dlencephalofl arid telence~lon is marked by the lamir~a affoca, a nan-ow roip of tef.. encephalofl that OYeriles the thalamus. It ar1 be seen that layen of gray matter permeiltl! the lntemil capsule In Its dorsi! portion. c U!wl of tfle nwnmllllry bodies: This section displays the thalamic nuclei. More than 120 separate nuclei may be counted, dependir~g on the symm of nomenclature used. Most of these nuclei an not be grossly Identified In anatomlal specimens. Their classtftcatlon Is reVIewed on p.216 (aftl!r Kahle and Frotscher, quOtl!d &om Vlllrnger and Ludwig).

~phelan

____:__.!....----~- Oxpuscallolam - - - - - - - - - - Clludatlenudws

...:__~:.____:.~?=::;:-!-- Septumpellucldam ------.,?!:......-:"""!~-- '--lwntrtd~ -----'~-------=+-----

IMII!IIIill ups...e

~r-~------~-------4-----~mk

lllenclephlllan ~~(~----~----~~~~~~--~~(~~----~----------~~--~~

• , •.,;.....________-

_____ t.ateralwntrtde

--:::;--:=-='=------.......,-- CArpusaiiGIUm - - - - - - - - - - ca~nudeus -

c.wum se~ pellucldl

lhlldwntrlde ---..,..--------=-==--------~ Oplktract _ _ _ _ _ _ _ ___;:.,......~

Medlllgro..,ofM.tdel Pnwntrtcula-nudel

----+--------------+-------~-------------­

lhlld wntrlde

Mammllodlalomle f•dtuiU5

Subth•llmlenudeus

-

1

------..:.===-

----+ -------------

Optic tract - -f:-:--::----:=..:::\.,

Mlnvnllarybocly

............. !Ubstlntla nigra

~-~

----------c

215

Neuroai'H1tomy - - 5. Dlfltcepholon

5.4

Thalamus: Thalamic Nuclei

~thillamlt---­

nudel Uf.iel'll postl!f!Cr - - - - -

nutleus

I

------

~~-~

nutleus

Ven11'alli!tel'll ~

~:~~;Jte ><xy nucleus

/

Vtntnl postl!folat.nl

nucleus Vtntnl postl!romedlal

nudtus Asandlng

too A FuncUon;~l orgilllllz.1Uon ofthe tNhmus Almo.st all of the sensory pathways .are relayed via the th~l~mm ;and proje« to the cerdlr.rl cortex (see G. thalamic radiation). Consequently. a lesion of the thalamus or Its cortical projection fibers caused by a stroke or other diJe<~K' IE.'ads to sensory disturbances. Although a diffuse ldnd of sauory pefteptlcm mayt.lke place at the thalamic level (especially p.ain perception), cortical processing (by the ~!encephalon) Is neces501ry In order w traru· form unconsclocls perception Into conscious perceptiOn. The olfactory systl!m Is an exception w Ull~ rule. allhocJgh Its olfactMy bulb Is still an exll!nsion of the b!lenQ!Fhalan. Nok: Major descending motor tracts from the cerebral cortexgener.illly bypass the th.illamus.

8 Sp;attal amngementaftflethillamlc nudear groups Left th.illamus viewed from the lateral ;and ocdpltal .iiSpect. slightly rotated relative m the vlewson p.212. Thethalamuslsacollectfon of appi'QXimately 120 nuclei that process senscry Information. They are broadlycliiSslfled <~sspe­ dflc or nonspeclfk:

The dorsal nuclei ire In contact with the the medial .ilnd lmral ge11lculate bodies. 1.0ated beneath the pullllnar, these 1:\\Q nucle;ar bodies cont~in the n~Kki oft#!~ tnftlial and loterol gmlatlak bodies, and are collectively called the mettlthalomus. Like the puMnar, they belor~g m the c.ategory of specific thalamic nuclei.

• Specific nudel and the flbers irlslr~g from them {th.illamfc radiation, see C) have dire« connections 'With spedflc are.ils of the c-. Oltll comx. The specific th~lamit nudei are subdMded Into focJr groups:

• Nonspecific nuclei have no direct connect!oruwtththecerebral cortex. P01rtof<1 gmer.!l.iii'DUS
• • • •

Anterior nuclei (yellow} Medial nude! (red) Ventrolatml nuclei (green) Dorsal nuclei (blue}.

C Namenchture of tile thalillmk nudel Properllll Specific thalamic nuclei (cortically dependent)

Palllothalamus

ProJect to the cerebral~ (pallium)

Nonspeclllc thalamic nuclei (cortblly Independent)

TNncathalamiS

Project to the br.alnstem. cllenaphalan. and mrp.. striatl.lm

lntegratlon nuclei

Project to other nuclei wlthfn the thalamus (classifeed as nonspecifiC thalamic nuclei)

lntralaminar nudei

Nudei in the white matter of the intemal medullary lamina (classified as nanspedflc thalamic nude!)

216

Ventrotmral

Itt alamlc nuclel

llledlai!Niamlc nuclel

AnUI'Ior Itt aIamie

nuclel

~~J I

medullry

lamina - - - - - - - lmmal medlllary I;Jmlna

D DMslon oftfle thalamk nucleT !Jvtfle medullary laminae

E SomatlltDplc orpniDitlon of the spedllc thalamic nuclel

Coronal section at the level of the mammillary bodies. Several groups of thalamic nudd ~re groJSiy separated Into larger nucle..r complelll!S by flbrous sheets called medullary laminae. The following laminae are shown In the dlagr.ilm:

Tr.anM!I'Se sectian. The specific thalamic nudei (defined in C) are ~ pographkally amnged according w thEir functional mal!on to specific regions of the body. Alfmrt fibErs from the spinal Olrd, bralnstenn and c:en!beilum .ilre local~ to speCific areas of the lhalamus,IM!ere the corti!SpOnllng thalamic nudei are clustered. This paUzm of somatDtopic arrangement. a recurrfngtheme In ~ral organllal!on,ls here lllustr.lt1:d for thevernroliltel'illhalamlcnudel (green In B. D, E). Ax.onsfrom the crossed sup.!11orcen!bellar pedunde1ll!rmln.iltl! In theventrallmrlll nudeus ofthe thal;rmus (2); infolmitign gn body position, a10rdillition and m~~Sele ll:lne tri!vels by1his pa1hwayto the moll:lr corte~c. ~k:h also !llOWS a pattern of $OINII:III:Iplc organlz.11Son (seep.339). The lotmll part of the venttallilteral nudeus n!lays Impulses from the extremities, while the medial part nelays im(dses from the head. TheVI!ntr.al intennl!diate nudeus (3) rec.eives afferent Input from the \'e3tlb\jar nuclei concemlng the GIOI'dlnatlon of gaze tllw.lrd the lpsllatrnl side. The large sensory pathw.lys of the spinal cord (the tracts ofthe postertor funlcui~~S) are relayed m the nlldel cuneitiiS and gracilus, ~ich ftl'ld their axons th~ugh the medial lemniscus 11:1 tenmlnate In the 1/elltral postlerolateral nudeus (4), lM!Ie the trigeminal 58\SOI)' pil1hwilys from the head terminate In the ventral poste~medlal nudeus (5, tngemtn<~l lemniScUs. seep. 275). Topographlc:ll localllatlon according 11:1 function is a basic principle of neural organiz;rtion.

• Internal medullary lamina between the medial andwntrolatenl thai· amicnudei • Emrnal medullary lamina between the lateral nuclei ~nd the retfcu· tar nucleu~ ofthe thalam~JS

ntr.Jiilmlnu nude!

a.

O!ntr.llthalamlc radlal!cn

F Nonspedllc thallmlc nuclel tte---=;;._-~~~=~-

Coronal sections presented in an oraJ.tl>caLJdal series. The nanspecific thalamic nudd project to the br~lnstem, to othEr nude! In the dlen· ceph;rlon (Including other thalamk nuclei}. and to the corp liS striatum. They have no direct connections 'With the cerebr.ill cortex. .ilctlng only indirectly on the cortn. The medial nonspecific thalamic nuclei are sub· divided Into two groups: • Nuclei of the cenlr.!l tha!;rmic gr.ay matte.- (med~n nucleus): Wtall groups of cells dislrlbuted along the w.~ll ofthethlrd ventlfcle • tntralamlnar nuclei, located In the lntemal medullary lamina. The largest nucleus ofthis g~p Is the centrcmedlan nudNS. The latEral $p«ific thalamic nucleus shown in the diagram is the reticu· lar nudeusofthethalamus. which Is situated later~l wtheother spedflc thalamic n~Kiel. The reticular nucleus Is the source of the electrfcallm· pcJises recorded In an electroenceph;rlogram (EEG).

lnimar INIamie radla!lon

G Tlllllmk nldiiUons

Lateral W!ntride of the left hemisphere. The axans of the specific thaJ.. ;rmlc nuclei (so called bee<~ liSe their flben project w specific cortkal areas} ;rre collected row tricts that fonn the thalamic rid lations. The .ilrrangement of the flbers shows that the speclfk thalamk n~Kiel have connections with all areas of the cortex. The an1Z!tiorthalamic radiation profeci:S tothefrontallobe. the «ntr;rl thalamic radiation to the part etaI lobe. the posterior thalamic radlal!on mthe occipital lobe. and the lnfe. !forthalamic radllltlon to the temporal lobe.

217

Neuroai'H1tomy - - 5. Dlfltcepholon

5.5

Thalamus: Projections of the Thalamic Nuclei

~~lgyt\IS

AtuGact

A Ventrolm!nl thalamic nudel: ilffefent

(aru4)

~ ~/~l~s

.nd effi!rent mniiKUons The ventral posterolateral nudc!us (VPI.) and ventral posteromedial nucleus (VPM) are the major thalamic relay C4!l1tefs for somatosensory Information. • Themedlollemnrscusends In the \ll'l..ltcontains sensory fibers for position sense. vi· bratlon. pressure. dlscrlmlnatlon. and touch that are relayed from the nuc:kus gr.-adlls and nuc:kus cuneatus. • Pain and temperawre fibers from the trunk and limbs travel through the lmral spinothalamic ITOct to latEral portions of the 11'1'1.. These sensations are relayed from this nucleus to the somamsen.sory cotta. • Pain and temperature lnformiltfon from the head regfor1 Is conveyed by the l1fgemlnol .system (• tJfgemlnothalamlc tract) tD the VPM. As in the Vl. they $Yf!apse with third· orda- tftilamlc neurons !hat project to the posttentral gyrus. Globusl);llldus.

A lesson o{111e IIJII..Ieacls to contralatEral disturbances of superficial and deep sensation with

dysesthesia and an abnormal feeling of hNVI· ness In the limbs (leslor1 of the medlallemnlsCIIS). Because the pain fibers of the spfnolha· Iamie tract terminatz in the basal portions of the VPL,Ieslons lr1 that region may additionally a use sewn pain ("thalamic pain"). The ven·

~ihegment

---~::;./

Glob~sl);llld~s. ~

lilt«111$e!iment

./

Pull men

tralllteralnudeus(Vl) projects tDsomatomotDr corlkal aneas (6illll and 6.afi). The Vl r1udel

form a feed bade loop with the motor areas of the mJUx. and so lesions of these nude!! are characterized by moiXIr defldts.

I Antll!rfornude415 01nd cmtromedlin nuc:le4ls: ilflen!nt ind eft'en!nt mnnec:tSons The anterior nudeus receiveslf/fen:nt fi~ from the mammillary body byway of the mammlllotilalamlc fasciculus (bundle ofVIcq-d'Azyr). The anterior nucleus estibllshes both afferent and efferent connections With the dngulatl! gyrus of tile telencephalon. The largest nonspedftc thalamic nudc!us is the centro median nucleus. which is one of the intr;~· laminar nuclei. It rec:eiYeS af(llrfnt (Ibm from the cerebellum. reticular formation, and medial pallldus. Its ef{rrettt fibers project to the heilld of the caudate nucleus ind the putamen. The centromedlan nudeus Is an important component of the -ding nrocular activation system (ARAS, arousal system). Essential for maintaining tfte w.rldng stite, the ARAS begins In the retlcularfollTiiltiOfl of the bralnstem and Is rebyed In the centro median nucleus.

218

Headdca~datle - -

~

G~::~.~~J

medlalagment

Embdtfonn nuclewof

/

Glob~s J)MIIW.$, ~l$egment

Pllt.lrrlen

affix!ilum

Mommiii;Jry

/.

body Retlwlilr fonnltfco of bnllnstenl

~

Ventrallmtal - -+ nucleus

--

- --=-- ++--+-

----1H-+-

uter.oldarul

nucleus

Do~lmedlil

nucleus

l.oltl!r.llgenlculale

C Medl;tl, dorsi~l, ;md lm!1111l tft;~l;nnlc nuclei: alferentand efferentconnec:Uons The medial tflalam!c nude! reaM! !heir .affl!l'ent Input from ventral and lntr.tlamlnar thalimlc nude! (not shown), the hypothalamus. the mesencephalon, and the globusfpallldus. Their efferent fibers project to the frontal lobe arid premGtor cortex. arid ill'went flbers fNm these reglor~S re!IJrn to the nuclei. The demucuon of these tr.ilcts le..ds to (ronttll fobt syndnlmto, which is char~rnrized by a IDS$ of self-control (episodes of childish Jocularity alternating 'With suspicion ind pe!IJiance). The doi'JIII nLJdel arefonned bythepuMnar, which is the largest nucle..rmmplexof the thalamus. The puMnar receives afferart:flben from other th.illamlc nuclei, particularly the lntrilimln.ilr nuclei (not shown). Its efferentflben terminate in the .ilstociation .ilreas of the parietal and occlpltil lobes. which lime redprocal connections 'With !he puMnar. The lateral genlcul.ilte body {part of the VIsual pathway) projects to the visual cortex. whi1e the medi~l geniculate body (part of the audltDry pathw;ry) profects to the illdltory cortex. The llltl!l•l nudel mnslsts of the later.ill dors;al nudeus arid lmral pDSterior nucleus. They ntPre:sent lfle dorwl portion of !he ventrolateral group arid receive their Input from other thalamic nuclei (henc2 the term •rntegrlltlon nuclei." see p.216). Their efferent flben tmnlnm In the parfetallobeofthebraln.

body

D Synllplll of some clnlc.tlly Important connedlant cltfle sp«ttlc

tfllllamlc nlldel The speclfk thalamic n~Jelel project to lfle cerebr;ll cortex. The table below lists the origins of the tracts that terminate In !he nude!, the nudel themselves, and the sites to which their afferent fiben project. 'llllllmllcnudeus (abbrevt.tlon)

'nl•l•mlcelll!rwds (SinumweiDwflfdl

•thi~UI)

Mammillary body

Antartornudeus (NA)

Ongulata gynus (Hmblc:systam)

Cerebellum. reel nudeus

Ventral lateral nucleus (VL)

Premotor cortalt (areas 6acx and Gall)

Posterior funiculus.IIIJ!ral funiculus

Ventral post~m~lateral nucleus (VPI.)

Postcentral gyrus (sensory oortex) •somatmensotyoortex(seeA)

Ventral post~m~mecll;ll nuclals (VPM)

Postantral gyrus (sensory cortex) • somatosensory oortex (see A)

Medial geniculate nud- (body) (MGB)

Transwne temporal gyri (audie.ry oortex)

'nl•l•mlc.,._rwds (Sbuduratl.a pnl)ect

the~usp,.._..)

(mammlllothlilamk fascklus)

(somatosensory Input, limbs, trunk) Trlgemlnothalamtc:nct

(somatosensory Input. head)

Inferior brachium (part of the audlbwy paltlway) Optic: net

Lateral geniculate nudeus (body) (lGB)

(part of the VIsual pathway)

219

Neuroai'H1tomy - - 5. Dlfltcepholon

Hypothalamus

5.6

A l.oc.1\lon of the hypottl;ll;!mus Coronal section. The hypothalam~&S Is !he lowest level ofthe dlencepha· Jon, situated below the thalamus. It is the cnly exb!mally visible portion of the dlentqlhalofl (SH D. p.213). Located on either side of the third ven!Jfcle,lts size Is most dearly appredated In a mldwglttll section that bisects !he third ven!Jfcle (see Ba).

•

"

l'
.

nudeus

FomiX

Hypo1Niamk sulcus

F
I

~--lf=·

D~

medial

nudeus

S~t~ nudeus

Pn!opdc nucleus VenlTo-

medial

b

nudeus ~opdc

nucleus

~

nucleus

dorulrs

:

PQsUrlof lobe of

pltult.uyglind

Tuberal nuclei

Mammillary bact;

Pomnor nude
I Nuclllln the right t.,pothala~ a Mldwgltt.illsecUonofthertghthemlspherellfewedfromthemedlalslde. b,c Coronal sectians. Tbe hypcthalamus is a small nude<ar complex lc· cated ventral tu the thalamus and separ.~ted from It by the hypothalamic suiCllS. Des~ Its small size, !he hypothalamus ls the command center for all aumnomlc functions In the body. The Tennlnologla Anatomlca lists DWr 30 hypcthalamic nuclei lccabed in the latl!r.al w.1ll and floor of the third ventricle. Only a few of!he larger, more dlnlcally Important nu· del ane mentioned In this unit. Three groups of nuclei are listed below In an ora~to
• Tbe .iln1lertor (rostral) group of r~uclel (greer~) synthesllle.S the hor· moner.relellSed f'rDm the pDS!J!fOOI' lobe of !he pituitary gland, and consists of the: - preoptic nucleus, - par.wentrlcular r~udeus, and - supraoptic nucleus. • Tbe middle (tuber;al) group of nuclei (blue) contrvls honnone release fromtheantertorlobe of the pltult
220

Doi'IOMedlll

lateral IS

l'lfundlbular nucleus

a

Thhl wnll!c:le

~-.-~

Opdc d!lasm

Antle!lor lobe of pltl.it.wy ~ind

Optic d!lasm

medllllls

TUberal nude!

c

Vtntromedlal

Third

nudeus

'f1!ntriclt

• The posterior (mammillary) group of nudel (red) activates the sympathetic nervous system when stimulated. It consists oftile: - posterior nudeus and - mammlllary nuclei located ln ttte mammillary bodies. The co~l section (c:) shllw$ the further subd'Msian of the hypoth~J.. amus by the fornix Into lateral and medial ZDnes. The three nucle;rr groups desafbed above .ilre part of the medllll zone. wflere;as the nuclei In the kltrral zone are not subdllllded Into speclfk groups (e.g., the ~ru late~ lis t~kes the pli!a! of ;a nucleUJ; the course of ttte fa mix is described on p. 205). Bllata'alleJions of ttte mammillary bodies and tttelr nuclei are manlte.sted by KI:JTSIDkaff .syndromt, which Is frequently associated with alcoholism (cause: vitamin 81 [thiamine) deficiency). The memory impairment tttat occurs in this syndrome mainly ;alli:!cts shorttam memory, and ttte patient may flllln the memory gaps wlttt fabrl· cated 1nfonna!lor1. Ama)or neuropathological flndlng Is !he presence of hemarrhage.s in the mammill~ry bodies, which are sectioned at autupsy to confirm the diagnosis.

strta tem'IN!Is

Folftlt

Ta rellculor

Mommlllothalamk

foml~

fasclcUus

Modlll Mrebr.oh bundle

PosWrior lobe ofpltullllry glllnd

•

Mimmllliry body

Peduncle of nwnmll•ry body

C lmportmt ~nt ilnd lfhrentconnlldlanJ of the ~liiiNIS

MlduggiUI sedlon of the light hemisphere VIewed from the medial Jide. Beausethe hypothalamuscoordi~~llthe~utonomitfunctions In the body, It estilbllshes afferent (blue) and efferent (red) connettlons with m11ny brain regions. The folklwlng are partlculirty lmporUnt

Afferent connedions (tD the hypothalllmus): • The fornix conveys afferent fibers from the hlppotampus: It Is an lm· po!Unt fiber tract of the limbic system. • The medial forebrain bundle transmits afferent fibers from the olfac. tory a !'ellS tD the preoptic nuclei. • The stria tennlllillls conveys affa'ent flbers from the amygdala. • The peduncle of the mammillary bodies transmits visceral afferent ftbers and Impulses from erogenous mnes (nipples, genltillla).

il

D FuncUo• aftt. h,pol:lalirmvJ The hypotha lim.us Is the coordinating anter of the autDnom ic netWUS system. There is no JPedflc sympathetic or parasympathitlc con· trol center. Ce!Uin fu ndlons can be assigned to specific regions or nudelln the hypolhali· mus, and these relationships al'l! outlined in the table. Not all of the regions or nuclei listed In the uble 1re shown In the drawings.

b Efferent connettlons (from the hypothalamus): • The dorsallonglrudlnal fiKlculus passes tD the bralnstem where It Is rell)'l!d s~l times before reaching the parasympathetic nuclei. • The nummlllotl!gmartal trad dlltrlbutes efferent flbers tD the tegmenrum of the midbr~in; these are then relayed tD the l'l!ticul~r fo,... matlon. The flbe.rs of this trad mediate the eJCd!ange of autDnomlc lnformitlon betvieen the hypothalamus, cran II I nerve nuclei, and spinal cord. • The '""mm~ lotha liomic fasdcu Ius (bundle ofVic:q d'Azyr) CQ~ efferent fibers to the anterior thai am lc nucleus, whim Is connected to the dngulall!d gyrus. This Is part of the Umble system (seep. 374). • The hypothalam lc-hypoplhyseal and tuberohypophyseal trads are efferent tracts to the pituitary gland (seep, 222).

Anll!fJOr preoptic region

Maintain constant body lilmperatu re; lHon: cent"'l hypothermia ~pond to tempentu~ changes,

e.g .. SW~e~~tlng;

Llllon: hypothermia Mldanb!rior •nd ,_terlor regions Pl,_,trltvlar 1nd ~nter1or regions

Ad!YIII! parnympilthetlc neNOUS system

Supraoptic and par.Mntrfcu lir nude!

Regulate \UII!r balance: Ullon: DlabtUs Insipidus. •lso lad< rJ thirst response resulting In hyponatremll Aegullta appetlbe and food 1ntale • ~Obesity • ~ Anorola and emadatlon

221

Neui'Otlnatomy -

5. DlmuplrGion

Pituitary Gland (Hypophysis)

5.7

-:--:--- lnflndbUor ~D!SI

- - - : - ' - - - lnflndbUum

\ b

A Dlvhla.. otdte~tarygllnd

Mlduglttill sections: a Sdlematlc representation. b Histological ap· pearance. The pituitary gland (hypophysis) cansirts of~ lobes: • Anterior lobe (adenohypophysis), tile honnone1)1'0C!'ucitlg part (see Dandf.),and • Posterior lobe (neurohypophysis), the honnone-rMoshlg p;1rt (see 1).

While the posterior pltultilry lobe Is an extension of the dlenc:ephalon, the antenor pituitary loi:Je Is der1Yed from the epithelium of the roof of the pharynx. The~ lobes establish contact during embryonic deW!Iopment. The pltlJitary mlk (infundibulum) attaches both lobes of the gland tv the hypothi limus, which contains the cell bodies of the neurosecretory neurons. The pituitary gland Is surrounded by a ftbrous upsule ~nd lin in the ~ 1\UtiaJ ~ the sphenoid ainus, which provides a route of surgical acuss to plb.Jitarytumors.

~~aug~

ondapl11mlc

rS!culum

l'llrt31 w.aels

Hemng body

--lf.~A-!.YJ~1

~IE£;'"'---1;!(.__

•

Inferior hypophyseal~rtBy

I Connccth1111 ofthe hypodMIImlc nuclei tv the postmar labc of lite pituitary tlilnd

• Hypothalamlc-{neuro)pltlJII:ary ms. II Neurosecretory neuron In the hypothalamic nucleus. Pituitary honnones 01re not syntlleslzed In the postrrlor pituitary lobe (neurohypophysis) but In neurons loated In the par-ntrlcular nu· deus and supraoptic nudiiiS of the hypoth<~lamus. They are then trans· ported by amns of tile hypothalamit-nypophyseal tract to the neu I'D· hypophysis, where they are releued as needed. Tennlnab of the p;~ra· Yl!fltricular ;md supraoptic hypoehalilmlc nuclei release ~ hormones In the post2r1or pituitary lobe :

• OJCytoctn fnlm the neurons of the p;II"IWntrlcular nucleus. • Antidiuretic hormone (ADH)« UIOfiNSJin from the neurons ofthe supraoptic nucleus. The uons from both nude/ p;ISS through the pituitary stalk to the posterior lobe of the pituitary gland. The peptide hormones are stored In vesida (~gregated into l~'lle "Herring blldies") in the cell blldies of the neurosea-etory neurons and 1re a n!td tD the posterior lobe by ilrltegrade ampliimk transport

Ventrcmed'al - --++-

C Hypoplryseel pottel d~UJI.uon and connedtor\S d tfle hypoth.allmk nuder to the <~ntarior pltult;ry lobe The sup«lor hypophysealirtelfes frGm each slde oftfte bodyfonn a vascular pltlWS around the lnfurwllbulum (plllllt.ilry sulk). The axons &om n~ui'WIS of the hypothalamic nucl~i (dart red and dark blue a~TVWS} tee" mlnate at this plexus and seaete hormones tflat have beal produced In smaller (parvocellular) na~rons of Ute hypothalamus. Tile secreted hypothalamic hormones 01re of two types:

11

nudew

• Releasing ficmrs which s!fmulate hormone release from cdls of Ute anterior pituitary lobe, ;md • Rl!lease-inhibiting f.lcbllrs IM!ic:h inhibit release from th~ ails. These hormonu are carried ~ tfle hypophyseal portal venous systan (nirned after Ute pcrtal drcula!lon oftfte IIIIer) to c:aplllirles In Ute anterfor lobe, establishing communication between Ute hypolhalam.a and mcloafne cells oftfle anta!or pltu!Ury.

·.

•

·z ~ophoblc

•• •• '

•••

... •

•

"--"·-·...,...

.-:7 ~ Balq)NIIc

•~

aUs

D Hlltlllogy of thuntl!ltor pttultlry gland Three types of edt can be distinguished ln the a~rior pltulury gland using classic histologic metftods: acidophilic cells, basophilic cells, ind chromophobic cdls. The litter have already released tftelr hormones, and are tfterefore negat~ in immunohistDchemical tem that speciftc<~lly detect pep1ide hormones: tfley are not listed In E. The icldophnlc (a) cells secrete h011Tl011es tft
Cllldell.......

Ho....-d-

Sommuopk (a)

Stlmu...llongltllcllnal growth; acts on c:arbohydratJt and llpld metabolism

PWoi.O(PIII.orLlM) Luteoti'Oplc honnone Mammatropk honnone

Mammotnlplc (a)

Stlmu...s lactauon and piOIIfelll!fon tA glandular bleast Usa.

Follltl'opln (FSH) Follld&-l!fmulalfng honnone

ConadotiOplc (b)

1\cts on the gonads; s!lmu~ follicular miltllratron. spEI'INII)genesls.

t.ltrapln (LH)

ConadotiOplc (b)

Sonwtloerlll* (SIH)

G~ honnone (GH) Somatotropic honnone

ellrogen proclucuon. e~qn551on of lutropln receptors and pn~llferatron of granulasa ails Triggers ovula!fon; stlmu~ piOirrer.on tA follicular epithelial cells,

production oftleslllsterone In lnteiSIItlal ~lg oells tA thetleslls. and synthesis of progaten~ne; has general anabolic ac:tMty

lnb!rstltlal cell samulaung honnone ·ICSH luteinizing honnone 'lbyrolropln (nH) Thyroid stlmu..lng honnone lbyrolropk honnone

ThyrotJaplc (b)

Stimulates thyroid gland aciMty; lnaeases 0 2 coMumpllon and pnoteln synthesiS; lnlluenCI!S calbohydrate and hpld metabolism

CDrUCDtnp.. (ACIH)

Adrenotrvplc (b)

Stimulates honnone production In adrenal mrtu; lnftuenCM water and electrolyte balance: acts on calbohydrate bmatlon In IIIIer

Melanotropk (b)

Nels In melanin formation and skin plgmentatro~~; pro41ects ag;~lnst UV

Adrenomrtlcolnlplc hormone Alpha/beta.......,.tn(MIH)

racrllllion•• • Cells are dasslfted as eltha- acidophilic (a) or basophilic (b). • • In humans, melanotropln- as a neurotransmltll!r lnWIIIOUS b~aln ~Ions.

223

5.8

Epithalamus and Subthalamus

,..... nude111

~-----------~~ ~~~~-~~~--~- ~~

•

A Loatton of the epltN..mu• •"''IIIUbth•l•mus Coronal sectlon. The appropr1iltaless of the term "epithalamus" Cin be ~ppreclilted In this pia ne ofsection, which shows the eplth~lamus rtdlng upon the thalamus (tpi • •u pon"). The eplthalam111 (green) c:onslsts of the following structures:

..

• Pln
-D.

a lJimtlonofthe piiiHI • Posteriorview. b Midsagittal sectlonofdlerighthemisphereviewed

The region« the sWthill- (orange). formerly ailed the ¥elltril thalamus, Initially lies directly Mlow the thalamus, but during embryonic dewlgpment Is displaced laterally Into the telenoephalon byfltMn ofthe lntl!rnal apsule, forming the globuspaiiJdus (see D, p. 211 ). The subthalamus
from the medial side. The pi~~SI resembles a pine c:one when III!Med from behind. It Is
~~r----~--­ CDmmlsiLre

.. ~

-rtor-....,..::- -

(eplllwlamlc)

a>mmlssure

•

224

..

C Stnumn of the plnul gl.nd 1

Gross mlwgltblllssue section. b Hlstologlal section.

In llle gross tissue section, llle habenular commissure c.a n be identified at the oral end of the pineal. Below 1t Is the posterior (epl· !hiIa mlc) c:ommlssure. Between the two commlssures Is the CSFfilled piRNI retenofthe third V1:ntricle. C.lciflations (c:orpori aren· icell, •b111ln s~nd") are frequently present and may be vtslble on radiographs; they howe no pathological slg nlflcance. b The histological section demonstrates the specific cells oftbe pineal. the p/Molocytes, whkh 1 re embedded In a connective-tissue stroma and ire sunvunded by astrocyte~. The pinulocytes produce m~ fatonlll, which plays a role In the regulitlon of circadian lhythms; 1t may be blaen prophyladlully, for eta mple, to mod.me tbe effects of jet lag. If the plne~~l ce<~ses to function during childhood. the lndlvtduiil may undergo precodous puberty,u the pineal hils significant, mostly inhibitory, effects on variouS endocrine $YSWns.

1

Fombt

Stria~hlillls

HabenJiclntl!!pedunalar

Stria me
tr.lct ~lnudeus

Pn!cptfc n!glon Ant!tfar perfor-m

su~ (cltadory ..-e.a}

Hlbenu~

Pineal Hlbenulatl!d:al tr.ICt

Quadrigeminal plm

lnb!rpedunC\dr nucleus

Hlbenul~ntal

tr.ICt

Amygdala Dcn'.al U.gnenul nudeur.

D HiiMnullr nuclei ;nl thelrfblr connectlonf Mfdsagltt11 section of !he right hemisphere viewed from !he medial slde. The habenula ("reins") and their nude! function a~ a relay st.rtfon for aft'~nt olfactory imP'JISI!S. After their rei;Jy in the h~berlular nudei. their efferent flbers are distributed to the s.1l!vatory and motor nudd (mastication) In !he brillnstem. Affinnt connectlons (bl~~e): Afferent Impulses from the anterior perforate substance (olfactory area), septal nude!, ind preoptfc region are triln~mltted by!he stria medullarls to !he habenular nude!. These nuclei aiJO realve Impulses from the amygdala via the stria termlnalls.

F«e's fleld H1

Elfer.nt a~mldlol'lf (red): Efferent flbers from the habenular nuclei are projected to the mtdbrilln along three tracts: • Habenulotectal tract: tennlniltes In the roof of the mesencephalon. the quadrigeminal plate, supplying ft wtth olfactory Impulses. • Habenulotegmental tract: tznminates in the dors.al tegmental n~ cleus, establishing connections with the dol'lilllongltudlnal fascl~ Ius arid with the sallvatory and motor aanlal nerve nude!. (llte smell of food stimulate~ s.illvatron and gastric acid seaetlon: e.g., PiiVIOYian respcnse). • Habenulolnterpeduncular tract: terminates In the lnte!pedurKular nucleus, which then connects with !he retlcularfonmatlon.

E Sclbth.Jiilmlcnucletwlththllr ilh!n!nt (bl~~e) ;md eft'el"'!fft (red) con nearThe prirKipal nudeus of the subthalamus Is the globus pol/tdus. which Is displaced laterillly during development Into the telencephalon by the internal capsule. A lamina of white mmer subdMdes the globus pallldus Into a medial (Internal) and latJ!ral (extzmal) segment. Cerbin small n~~tlel are ellempt from this mlgriltlon and remain near the ml~ line: these are the zona 1t1cmu ind Sllbtholomlc nucleus. The subthilllamic nucleus. substantiol nigra, and putamen send afferent flbers to the globu~ pallldus. The globus pallldus In tum dlstlfbLJtes effi!rent flbers to these regions and aiJO to the thalamus through a tract called the lenticular fasdculu~. Functionally, these nuclei all! classified as parlions of the bas.il 9'fnglla. lesions of these nude! lead to a movement disorder called ccntralateral hemib.allism (the functional role of the subthalamus Is deKrlbed on p.340}.

225

6.1

Brainstem, Organization and External Structure

A Tenns of IOCiltSon 01nd dlrec:Uon In tfll! br.llnstl!m These terms are based on the nearly wrtlul Meyllet bralnmm oxts (comp;~re with thl! harizgnti!l Foret ~s. which WillS used iS a refl!rence

lrne In previous units). just don<1l to the br.rlnstem Is thl! cerdlellum, which 'Will be described In chilpter 7.

B Rll!laUonsh_, af the br.llnsb!m to the c:ereflr.lli!nd c:Hebellar hemllphen!s Bll5al view. The briinstem is i midline Jtnucture flanhd by the cere-

bnum and ardlellum. Its anatomical subdivisions are best apprediltl!d In the mlds.-.glttal section (see C). The third tflrough twelfth pairs of cranlallli!M!s (CN III-XII) enter or emerge from tfle br.rtnstl!m (see E.t}. D Overvtewofthe bralnmm

Dltn---aphalon __

-r

TopograpNQI 01111n11Daon • Cl'clllloaludCI dlrfdlon:

-

I

aphalon ~ ~

~cephalon (midbrain)

-Pons

Me.sen-

- Medulla oblongata • An~dftdlon:

- Base (mese~alon: ~I pedundes: pons: basal part:

medulla oblongata: P'JI'lmlds) - Tegmentum (presenus such inallthree parts) - Section of wntrkular system (upper part ~I aqueduct. fourth wntrlde, centnol canal) - Tectum ("roof";presentonlylnthe mesenoephalon: quadrigemi-

nal plate) • Tbe cerebellum ad]Dtns the bratnstem dorsally.

c

DMIIon oftfldntftlf:l!m Into ll!'lltll Mldwglttal section. The br.llmtem Is divided macroscoplully Into three lewis, with tile bulge of tile pons marking tile boundary lines between thl!parts:

• Mesencephalon (mldbr;aln) • Pons • Medulla oblongata

The location ind contents of thi:IK' parts are summarized in D. The three lewis ;are easily distinguished from one ;anotfler by gros.s visual Inspection, ;although they ;are not dlfferentliltl!d In .-. functional sense. The {r.md:fooal orgonJmttoo of the briltmtem (see D) Is determined chiefly by the arrangement al the crani;d ne~ nudei. Given the dose proximity af nuclei and large flber trilrn In this region, even.-. small lesion of the br;alnstem (e.g.. heiTIOITt!;age. tumor) m.-.y lead to extensive ;and complex alter.rtfons of sensorimotor function.

226

Alnctlclftll arganiDIIan

•

~lnfotiwT~nudeclraJ/umfls:

-

Somatlceffmnt(motl)r)column Vlsceraleffftnt(motar)column Visceral ~nt (sensory) column Somatlcarr.rent (senJDry) aalumn

• ~lniJodl(frnnt~ - Nudel of cran"l nerves III-XII

- Red nudeus. substantia nigra (motor coordination centers) - Reticular formation (diffuse nuclear aggregations for aulllnomk functions)

- Ascending and descending tracts (seep. 232) - Dorsal column nude! (nudeus gracilis •nd nudeus aJneal11s)

- Pontine nudel

Neu~YU~rurtomy - - '· BnJlnstwn

Oallcmolor ni!M.'(CN Ill)

PoM

TrlgemlnaiMrVe.

Brad!lumof tnfetlarcollcuha

lntapl!d..,cullr fOSH

~

~

l

~Qemlnal

plate.tnfmor coltcul
·~•"""'-'

motor~"" ~

Trf9tmlnal .___ ntM(CNV)

J

Trigeminal OeM.'

Abcllant

ntM(CNI/1)~ F.aclalntM .............._ (CNI/11) "-.., Nenna _____r 'ht2mledl
\

~~~/ ~ ; . ~)Clouophal)n!leal netW (CN IX)

..:;

-

\lagUSneNe(OilC)

HypogO$$;llneM (CNXH)

I

AcamryneNe (11j)ln~l new,

(CNXl)

DecuW
ve<1tllii!Wt

ofpyr.~mldr.

Unbnll P'!Wnde

Br
E llnllftltl!fn • Anteri~rview. Thnitnofentry~ndem~ence~ftheten pail"5~fttu~ cr;mlal nerves (III-XII) are partla~latfywell displayed In this 1/tew. Nobl!: Cranial nerve II (opUc nerve) Is a derlvatllle of Ute diencephalon. Notealsothesltebelowtftepyramldswherelbepyramldalflbers cross CMr the midline from each ~e (clecussatian of the pyramids). Most afthe a1!Dru af Ute large matorpilthw.!yfarthetrunk and limbs cross tD Ute opposite side ilt tftls level. b Posterfor lllew. Slna the cer1!bellum has been remCM!ld, we can see the rhamboid fllssa, which farms thefl~raf the fourth ventride. The surface af the fossa Is raised by sever;rl cranial nerve n~Kiel, which bulge lntD the faurth ven!Jfcle. The cerebellum Is connected to the br.ainstl!m by three c.en!bellar peduncles on each side:

• Supel'for cerebellar peduncle • Middle ~bellar peduncle • Inferior cerebellar peduncle The superior and Inferior cerebellar pedundes border portions afthe lflombold foss;r and tftus contribute to Ute boundaries af Ute fourth ventrlde. c Left lateral view. In addition to the (etebellar pedundes, this view displays the supafor arid Inferior collla~ll. Together with their counterparts on Ute right side, Ute callfcull form Ute quadrigeminal plate (see b), which Is a prominent muct:ure af Ute mesencephalon. The two superior a~llia~li are part of the visual pathway, while the in~ riorcalllcull are part afthe audltDry pilthway. The trochlear nerw (CN IV) runs farwand below Ute Inferior callfculus. and Is Ute only cranial nerve that emerges from the dors;rl side of Ute br.illnstem. Theolrve appe<ars as a prominence on the side of the medulla oblongata. The nuclei within the olive function a~ a relay station far the motor system {seep. 342).

2'Z7

6.2

Brainstem: Cranial Nerve Nuclei, Red Nucleus, and Substantia nigra

Vlser.ll oculomotor (£dhl51~0 nud~

Trigeminal ............__ . ~

mo!Drnudeus

of-----

Nucleus abdUCI!nl MrVe

----_

2

Fildal-----""' nucleus

Superlorsoltv..-

/;{v

~="::ry / Y nudeLS

Nucleus amblguus

Darsalval)ll nudeus

•

h

/ '

Nudeusof

A Cranl•l net"Ve nucleT In tfle bnllnrtem a ~rlorvlewwllh the cerebellum removed, exposing the mombold fossa; b Mldsagllt
which give rise to the efferent fiberl, are shown on the left side of di<~­ gr.am "'·and the 5fnsol)' nuchl. where the afferent fibers tennlflilte, are shown In b. The ammgement of these nude! can be deriwoed from the ;ur.angemmt of the nude! 11'1 the spll'lal cord (see p. 611). The function <1nd connections of some of these cranial nerves can be dlnlcally ev~lu­ ated bywtlng the brolnstml rrflf;Kts (whose rday anters
scribed more fully on p.363.

Malar nude!: give rlle ID t.ffeA!I'It(mDIDr) tlbers,left In All

Sen.-y nude!: where afferent (sensory) fibers tlllmlna, right In All

Somltlcelrwetltottometk IIIOIDr nudll (reel): • Nucleus ~oculomoiDr nerw(CN Ill) • Nucleus~ trochlear nerw(CN IV) • Nucleus~ abducent nerw (CN VI) • Nucleus~ acceaory nerw (QI X9 • Nucleus~ hypoglossal nerw (CN XIO

S.....tfc. . . .nt(w....tkNnMI'YJand-...QICh.... nudll.,..low): Stnsolynuc/tl assoda«dwflllllleOfgflnlncrlnetW (OIVJ; • Mesencephalic nucleus of trigeminal nerw (spedal ffttur.: pseuclclunlpolar ganglion cell~ ("displaced sensory ganglion"). PIO'IIde direct sensOI'f innervation for muscles of mastication) • Principal (pontine) sensory nudeus oftrigeminal nerw • Spinal nucleus ~111gemlnal nerw

Vl_l'lil..,..(ljl-ralmotor)•dll: Nurk/ofllle~dlltornerw(tlVWI); Nurk/GDOdufedwllllllle~nenour~

(Jightblw); • VIsceral oculomotor (Edinger-Westphal) nucleus (CN IIQ • SUperior w!IIIJIDry nuclws (facl;ll n-. CN VI~ • Inferior sall'latorynudeus (glossopharyngeal-. CN IX) • Dors.~l wgal nudeus (CN X)

o Vestibular part: • Medlalvatlbularnucleus • Lllmral wstlbularnudeus • SUperiOr vestibular nudeu~ • lnferfor wsUbular nudeu~ oCochle.ar part: • Anterior cochlear nudeus • Posterior cochleer nucleus Vlsczn111 alferent(ljllll!nlll - r y ) •del (...,):

Nude/ of!lie lnndtiol otdt- (dart blw): • Trigeminal moiDrnudeus (CN V) • Facial nucleus (CN VII} • Nucleus amblguus(gl-pharyngeal nen~e, CN IX; wgus - · CN X: accessory nt!W, CN XI. cranial root)

228

• Nucleus oflht solitary tract (nuclear complex): o SUperior part: • Special visceral afferents (taste)from facial (CN VI~. glossopharyngeal (CN IX). andvagus(CNX)o Inferior part: • General VISCeral a~rents from otossopharyngeal (CN IX) and vagus (CNX)nerves

l'illdum

C l.aut.,noftbl!substantl.nfg111andn4nudouslntfle

-~··

Both of these nuclei. like the aanlll _... nuclei, al'li' well-defined structures that belong funcUonally 10 the ~ momr system. An· atDmically, the subsunlia nigra is part of the cerebral pedundes and thl!n!fore Is nat lacatld In the togmentum of tbl! .......,cephalon (see A. p. 234). OWing ta their high respertlvle oonlllfltS of melilnln and Iron, the substantlo nigra and ..d nucleus appesr bnlwn and ra:l, l'li'spoctlwly, In sections of fresh b~ln t~. Both nlldd eltend lnta the dltncephilon and are CDilned:ed 10 lb nuder by nbertracts (set£).

Cen!brol

aqueduct

----=---

Rllld----=:--~d-

.....;:.,....--Tectum - - - - - Togmt!llbm -C....bnl pedLI1de !!1Jbsbntlo

•

n9a

l'ubomen

. ~j

llalarpart afpan•

1 - - - - - - - CeniAI 01\11

c D cn~~-•dl-1 druclln oftfle bniiiBIIm • dlffenniiiWI• Tl'11nsverse MCtlons through the 1 meHncephillon, b pons. and c medulla ablongatl, viewed from abaove. A futul'li' a~m mon 10 allllll'fl! stc:tlons Is the dar$ally sltwted tegmentum ("hood." medium gray). the phylogenetically aid part of the brainsb!m. The llllgmentum af the adult brain cantalnslhe bralnsll!m nudel. Anterlar ta llle tegmentum iiA! the lilrge -ding and descendlng tricts that run 10 and fram the telenc:epholon. This region is called the c:el'li'bral pedunde (cnus aol'li'brf) In the mesencephalon, the bui~Jr part (foat) of the pons at the pon. ane lev.l, and the pyramkls In the medullil oblongata. The tegmentum Is CJM!!ra:i darnlly by thellllctum (• "roof") only In the regl..., af the mesonaophilon. In the matul1! brain pictured hel1!, this stnlctul'li' hlrms the qui16r1gemlnal pliltr callUinlng the JUperlor and lrftrlor calllaJII ("little hills"), s'-n f.olntly In 0.. The braln>tlm II cawrecl by the cermellum at the level ofthe medullil oblongiti 1nd pons and th~Mln Iiides 1 tectill CJMI1ng at those levels.

E Nfll!rent (lllue) •nd ....,._ (red)-.-tlo• Dfthe rell n..teu. illlllsullltinltil ..gra These two nudel a.elmporant relily st.t~ons In the momr system. Them nucleus CDilsisb af a larger neDnlllnmland a smaller~· It recelvles afferent ~J~Dns from the denbte nuclals (dentatorubr.~l trict), superior oolliculi (tectorubral tract), inner pallidum (pallidoNbraI tract), and ~ br.ll corta (cortfoxubral tnlrt). The red nudeus sends ltnXDns 10 the olive (rubra-ohviry ftbers and reaculo-ollvary ftbers. part of the central llegmental trict) and ta the spinal mrd (rubrospinal tiKI:). It mordlnatls muscle tnne. body poslt.,n, 1nd g;~lt. A lesion of the red nucleus produces resting tremar, abnarmal musdetnne (tested 11 IIWOiuntary muscular rtiistance of the joints In the ra.m!d patient), and choreoathetosis (lnwluntary wrlllllng movements. usually lrTfOivlng the distal parts of the limbs). The substantia nlgno consists of a c.ompcrctpart (dart., amtains melanin) and a miwlarpart (reddish, contains Iron: hlr s1mplldty, the entfre substllntlil nigra appe.ars dark in the drawing). Most of its -ns project diffusely to other brain areu and are nat c:allectad Into tracts. AIDns from tbl! audate nucleus (strl.atx>nlgral fibers), ilnterlor arebr1l cartex (cartfCDillgrill ftbers), putilmen, <md pn!DI!nt11111 CDrtaterminate in th~ sub>llnlia nigra.

229

6.3

Brainstem: Reticular Formation

Nucleus of

owlomotornerw

Nude!ilr ~on forvlsual or!entrtfon In sp;Jte.auttJnomlt «
l'c6tlerfarraphe

nudeus

Trfgemtnal mater nudeur.

A

StrudlU'I~funcUonal reltrtklnshl!S In tfle retfcularfonnatTon Midwgitt;~l section of the br;!inrtem viewed ~ the left side. Wflile

8 Nudear reglons and ncuroer.nsmltters In tfle retfcular

ttle cranial nerve nuclei, sulm:antla nigra, and red nucleus hil\le wdl-deflned boundaries, as we have seen, the reticular forma!Son (light green) Is a relatively diffuse net\WIIic of nef\11! cells ~nd tlbers In the bralnstem, ocupying the areas betwc!c!n the cr;anial nerve nuclei described abiM!.It can be roughlydtvlded Into two main groups afnt.rdet

Posterforvlewofthe bralnstem (cerebellum remOYed). Retlcularformottlon shown In green. Several nuclear regions and neurotransmltten are shown here. left side: classification of the nucl~r regions; light side: distribution of neurotransmitten in the nuclear regions. The nuclear regions ofthe retlcularform.rtlon can be classified bythdr location (medial Gr later~! groups of nuclei, see A) or by the neurotransmitters they contain:

• MH/al group (spedflc nudd labeled In tile diagram): nuclei oontaln· lng lGrge neurons'Wflose axons fonn long ascending ;md descending tr~ct!. (see E). • umwl grt111p (not individually labeled in ttle diagram): nuclei ton· talnlng smalll!Wronswhose axons usually st<~ywltttln tile brillnstem. They are lherefore ailed "assocla!Son areas.• Besides ll!'lplratJxy and dmslatory lf!IU!atlon, the diffuse neuronal net· work of the reticular fonniltlon performs many other Important autG· nomic functions that ~re mapped In the diagram neurotr~nsmltten. Diagram 8 shows several nuclear regions and their neurotransmitters In some detail.

230

fo~on

• • • • •

Sei'Otonergk (purple • serotonin) Cholinergic (red • acetylcholine) Noradrenerglc (light blue· noreplnephrfne) Dopamlnergk(orange =dopamine) Adrenergic (yellow• eplnephrfne)

The nuclei !hat flank the midline are called the l'flllhe nuclei (shown In purple,. r~phe • •seam"). They contain !he neurotransmlttl!r seratonln, and their neurons project to ttle hypothaloamus. lrmblc system, and neoo;ortex. The locus mulcus (shown In blue, caenuleus = •blue") Is aregion that ~ctiJ~IIy ~ppears blue In the fresh brain. This nucleus contains noradrenergic neurons which send .axons to the cerebellum, hypothalomus, and cerebril cortex.

Neu~YU~rurtomy - - '· BnJlnstwn

Nucltwof ~loualn~

•

I

Nudeu.of

~ the,olll:llry

~

trxt

---Nudeur. amblguta

c RtsplratDry Cll!nter In tfle rea:c:U.. fonNtSon a Posterior 11few with the cerdlellum removed. b Tr.msverse section at the level lndlated, showing that the two nuclear groups in • do not lle In the SOl me vert!al plar~e. An lmport
b

D Orculnllry center In the rftl~l•r fonmtkm oft:he Cilt (after Kahle) a Oors
E Brandllng pllttl!m of a neuron In tfle nettc:U..formatTon afdle rat bnlnlltem

......_,=-~..-.--..----

Nude! In the br~lnst.em

(after Scheibel) Mldsagltt
Neuron

231

6.4

Brainstem: Descending and Ascending Tracts

Cortfconudmr lb!B

A Dacendlng tr.Jets In the bl'lltllltem a Midsagittal sect1or1 viewed from the left side. b Pomrior view with the cerebellum removed. The descending tr.-acts shown here begin lfl the teler~cephalofl and tennlnate partlylfl the brainstem but mostly in the spin;al cord. The most prominent tr.-act that descends til rough tile brilnstem, the cortJCDspltKll troct, ter· mln.-ates In the splnil c:ord.ltsaxons alfsefrom large pyramidal neurons of the primary motor cortex .-and terminate on or ne.-ar .-alpha motor neurons In the anterior horn of the splnil cord. Most of the u.ons cross to the opposite side (decussate} at the level of the pyramids. The fibers In this part of tile pyr.-amldal tract thit descend through tile bralnstem are c.~lled corttc:osplrtol {Ibm. Those flllers In tile pyramidal tract that termin;ate ir1 the brain· stem are ailed cortlcot!UdfOr {Ibm. Cordconuclear ax.ons connect tile motor cortex to tile bralnstem motor nuclei of the cranial nerves. Nott-.: Direct cortlc.-al projections to tile brain· stem nuder ane predominantly: • b11atJ!nll for:

- tne trigeminal motor nucleus (CN V) - n~rons In the fadal nucleus (CN VII) tilat lnnew.~te musdes lr1 the forehead - nudem amblguus (CN X) •

Red nucleus

Nudeusof oc:ulemotorne<W

n-t\:\lc'=-....:::.....,;:1-.- - - - Trfgemhalmollr nucleus

""\t-7"--:r~---

Faclll nucleus ~-t~::-"''-=~---

nud~ of tile

~501Y-

• Cortlccnuclen

abducent nerve (CN

----,,--~

flbefr.

VI}

-

Nudeusof hypoWa:ssal !'!eM

T 'll--1--- - - - Nudeusot

c:ontrolotw~JI(=ssed}for.

- tile

Nudeusof llbducert neM

n~rOIU In the fadal nucleus (CN VII) tilat

lnnew.~te musdes lr1 the lower face -tile nucleus of tile hypogloss.11 nerve{CN

XII)

• ipsi1otLn7/for: - n~rons In the nucleus of the aa:essory nesve (CN XI) ti1at lnnervite tile stemodeldomastold muscle The Pittml of cortlcor1ucle.-ar lnr~erYatlon Is lmport.1ntlnthedligfloslsofdtfferentleslons. pi!rtlcularly lnvolvlr~g the facial nerve (CN VII; seeD, p. 79). Mo.st cortical projections to tne bralnstem motor nuclei. however, are lndl· rect. Involving lntermedlite neurons. m.-any of which ane located lfl the surroundlflg retl· a.lar formation. Direct a~rtical control of br.-alnstem motor n~rons, spedftallyfortile tongue .-and face, seems to be a recent evoIUUonary development, present In primates but not ifl other mammals. The nuclei of tne oculomotor (CN 110 and trochlear (CN IV) nerves, which do not recefve direct c:ortlc.~l projections. are synaptically connected with tne abducent nucleU$ tnrough the mt:dif/1 longitudinal (asctcufus (see D.p. 321). ;a brain· stem tr.-act thilt c:ont.11ns both .-ascet1dlng .-and descending fibers.

232

~t---f"t------ Nuclewof abduczntn~

FOidil nlldeus

b

Neu~YU~rurtomy - - '· BnJlnstwn

~L-------~--------To~

t«tD

SuperiOr a~bdlat

r.==.~,...-.....,;_~--- t.a~«al

lemniscus

pedunde

Ml6cte a~bellar

pedunde O~ilr -~~"">«;!!.\~""

~h~T-~+-- ~ar

tn1ct

a~bdlar

01~

pedunde

Anb!llor ---~\ \\\-+- - - l'l:lm!IIOr splnocerebdilr splnoanbellllt

•

tract

tnct

lemnllcus

Nudeor. ~·~

----~ ~r---~;_

____

Nucleus gradlls

---:.-=+---- Antnr

F.Mdcull.ll ----~--'il'll ~·~

111--f~---

FasdcuiL5

splnoccrebeltlr

gradlls

tnct

b

I Ascending trub In the lminstem ;a l.dt lateral view, b posterior view. 1Wo ma}or ascendlf19 flber bundles, !he

posterior funlcdus {violet) and tile lltltralsplnotfllllmlt tratt (dark blue), carty sensotyinforma· tfon from the spinal cord to the bralnstem. The posterior funiculus con· s\sts ofttle medial {osda.tlus gracilis. from !he lower limb and trunk, and ttle lal:c!ral fll5dallus cuneatus, from ttloraclc <~rid ce!'VIullevels. Many of ttle fibets in these tracts are the central processes or dotsal root ganglion ails ~ose peripheral proanes are In musde spindles and ten· don stretch recq:rtors {proprioception) and cutaneous to~Jeh receptors. The ffnt SYfl.ilpse In ttlls ascendlf19 pathway Is In ttle I!Udells graciliS Gr nlldew: atneotlls; the neurons from these nudei send their axons in ttle mf!dlal lfmnlscus (lemnlskos - •!fbbon." Gr.) across tile midline to the ttlalamus (see p.216, 218). The later<~l splno!Niamfc tract bears pain and temperature Information from secondaty neurons In ttle contralat· era! spinal CGI'd. passir~g without an additional synaptic relay directly tD the thalamus. The ottler ribbon-like sensotytract In the brilnstem-ttle latl!rallfmnls· ws- contains axDnS from tile cochlear nlldel, some of which aoss ttle midline in the trapezoid body, to SYfl.ilpse in the infl!rior mlliculus orttle quadrigeminal plate.

b

C CaunH or the m1]or a:rebclllrtrub through the brlllndem Midsagittal sectlon viewed from the felt side. b Posterior 11tew .tth the c:erellellum remcwed. The cerebellum is involved in ttle CDCrdination or mOVI!!ment. DescendIng tracts (red) arid asc:endrng trim (blue) enter the arebellum through ttle superior. middle, and fnferfor cerebellar pedundes.

;a

• Supertor anbellolr padundc contillns most or the +ent ax.ons from ttle arellellum (seep. 242). The only major of(rrettt axon tract entelfng ttle cerebellum tllrGUgh the superior peduncle Is tile ant2rior ~inocerebel~r p;athwiy. • •ddle cerebelllir peduncle: largest of the tllree pedundes, occupied mostly by gffmntflbers from contralateral bini pontine nlldel. These
233

6.5

Mesencephalon and Pons, Transverse Section

A TN-a.UonthiWihthl n-latpMion(mldllnlll}

Nucllf:Themostro~>tralaanfalntnll!nucleus

Superforvlew.

Splnallcbl

s.......,..mlllnlllr

tract

nud...

\ =e.~~

MllllnCl91wllc nudtill oftJ1genltnii..-

~

~ ~~

is the relatively small nucleus of die OJtUiamolvr llf1W (see I, p.226). In the same trln!l\Bradlk.lm~nfsll'-·lousr---~ ~loympalhdlc wrse plane Is the m~llc nudftts of the ... ~ tnld trigemincr/-; oth~ trig'"'in•l nuclei C=cui: gllon (both populations are derived embryonpontine fibers ( ~~ blly from die neural crest). The peripheral prvc:esses <#these mesencephalic neurons are / Rled proprioceptors In die muscle~> of maslkatlon. "::~= nucleus The supf!rfor CDII/aJ/or IIUdet.cs Is part of die Illond mrtlcosubmntlo sllill system. The rfd rnK/ftn and ~ntto n1spinal flbers rlgro gro :~re fnvolwd In coordiNtlon ofmotonctl'r Cartlmpontlno "Jectmplnol ModoI Oallomotur ity. The 1M nutleun nd all ofthe cranial nerve tract tr.lcl lemnllcus nuclei are locited In the tJegmentum of the mesencephlllon, die superior collfculus Is In the tectum (roof) of the rnesenaphalon, and medial lemniscus. both of which tenmlnate In TrKts: The tracts at dlls level run anterior to the substintli nlgrills In the cerl!bral peduncle the nudeilr regions. Prominent descending die thalamus. (see c. p. 229). Diffetent parts of the reticutracb ~it this lew! include the pyramidal trilct and die cortlconudeJrflben that branch lir fumniltlon, a diffuse aggregltlon of nudeilr groups (see p.230, 231 ), arevisible here and In from ft. Ascending tracts visible at dlls lewlln· sections below. dude the lateral spinothalamic tr;ct and the

y

/

I

B n.-s.Uonthrouththl upiMf' parw

Nudlf: The only cranfill nerve nucleus appNrlng In this plane of section Is the mesencep~ illlc trfg'"'lnal nutleus. It can be SHn tiMt the ftbers from the nudeus of the troc:hlear nerve (CN IV) cross to the oppo$ite side (decussate) while sdll within die b11lnstem. TrKts: The ~sanding ll nd descending trut systems a~ the same as In A 1 nd C. The pynmfdal tract il ppu rs less compact at this level compalM with die previous section due to the p~senc:e of Intermingled pondne nuclei. This section cuts the trac:ts (mostly lllferent) ttut exit the ~bellum through the superior arebellir peduncle. The lilterlllemnlscus 3t the dorsal surf.oa <#the section is part of the a~ dltory padlway. The relitlvely lirge IJiftllallongfrudiNI fasdcul us ubtnds from the mesencephilon (see A) Into the spinal cord. It Interconnects die b11lnstem nuc:W 1 nd contains 1 variety of fibers that enter and emerge at v.uious levels ("h~ of the brainmm nudlt"). The smaller domJIIongftudiNI fasciculus mnnects hypothaliomic nuclti with the pa,.ym-

234

>---~-- Pyrornfclll tract

pathetic cranial netve nudei. The size and lo· atlon of the nuclei of die retiOJlar form~on, which here are shown graphically within :11 compact arr<~, ~with the plane <#die sec·

tion. This diagram indicates only the approxirNte l.oc:atlon of the retkulir formation, ;md other smaller nuclei and flben may be found within the'f regions.

Neu~YU~rurtomy - - '· BnJlnstwn

Splnalnucle111of---trlgem'hal nerve - - - - - - - - - - --':--- - llledlallang1111cfnal fardaJiw;

Tecto:~plnal

Inlet

~lrlgen'inal I'M!I'W

Mecfal JemrfKIIS

1hlcb: This section cuts theanterforsplnocerdlellar tr.1et. which passes

C lhi-FA section tfn'Oilgh lhe mldportlon of tile pons Nuclet: The !Jfgemlnal ne!'Ye le.ilves the bralnstem at the mldle~~el oftfte pons, Its varloca nuclei domiDatfng the ponlfne tegmentum. The pi'tn· cipQI-r nuciM" of the trigeminal nerve reli!Y$ aff~nU for touch and discrimination, wfllle Its !pinal nucleus relays pain and temperature flbers. Thetrlgemlnalmotornudeil!icontalnsthemotorneuronsfortfte muscll!l of mastlcatlon.

to the cerdlellum, rmmedlatelydors<~l to the pons. CSF tp.IIC)I!: At this level the cerebral aqueduct has giVen way tn the fourth ventricle, wflicfl appe.1rs in CI'O$$ section. It is o:M!red dol"5ally by lfle medullary ~um.

Embollfonn

nudeus

Sort;rytr.Kt - - - - - - - - - -

-

- - - - - - - - - - - - - Medlillonultudlnal

fll!ida.ius

C8m~::.~. ~ . ~ ~ tllgemilllnen'l' Anttflor splno-

£.

«rd>eelilr~

7

.4

Fadalnudeur. Cl!nlni~!!!Jne nbll

lr.ac:t

lll.tlra:tplnal

~.<~Uralsplno­

tract

thalarrlctract

D TniMWrte teeaon til rough the bwr pans Nuclet The IDWer pons contains a number of cr.anial nerve nudei in· dudlng the nuclei of lfle vest!bulocachlear and abducent nerws, and the facial (motor) n~~eleus. The rhomboid fossa Is COYerecl dorsally by the cerebellum, whose nuclei also .ilppear In tftls sectlon-tne fastlgl.ill nudeUJ, emboliform nucleus, globose nucleus, and dentJtl! n~~eleus.

Tl'8ct.t: The trapi!Mid body ~th Its subnuclei Is an Important relay station and crDSsing pointin the auditorypathway(see p. 366).The central tegmentaltract Is an Important pathway In the motanystem.

235

6.6

Medulla oblongata, Transverse Section Dorsolwgal nudous

....

Nudous of hypaglaoul.,.,.,.,

·.;J

llhcmbald

-==~\A ......:: ~ Sptlal...,clousof---- lrfgo:mlnll n~ -----_

c.ntnlrtmpmt.ollc

D

- - - - - - - - - - - - - -- Medlallongltudillll f11dc:uha

~

::.. /< ce~bdlarma

/

~ ltl!tlcul•r formallan

Medial lomni!Kll!

A T l ' l -tedfonthroughthe upper medul• oblongtt~ Nudlf: The nuclei of the hypoglossal nerve, vag us nerve, 'tleStlbul()cochlear nerve, and the spinal nucleus of the bfgemiNI rww appear In the dond part of the medulli oblon!Jilta. The Inferior olivary nucleus, which belongs tD the motDr system, Is louted In the 111111Tal part of the medulla oblongata. The Mi
transwne SKtions of this unit. Trids: Most of the ascending and descending tracts are the same as In the prMocls unit. A new structure appearfng at this IIYI!IIs the ltrfrriDr ~r pnhmck, thrvugh whkh alli!rent tracts pass to the cerebellum (see p. 242}. CiF tll'ce: The floor ofthe lou rth wntricle is the rhomboid fos.sa, wh ic:h marla the dorsal boundary Gl this section.

PyRmlclol

Medlol

tract

I1!11'11IICIII

8 1'111-•edfonJult•bvw the middle of the medulla oblangm Nuder: The only cranial ne'W nuclli visible at this level are those t# the hypoglossal nene, vag us naw. and trigeminal nene, 1ppe;1ring In the dorsal med ullil. The I.CIWI!r portion t# the Inferior olivary nudeus appem in the ..ellWI medulla.

filM

Tnds: The ascending ind deJUndlng tr.m ire the same u In the previous unit. Ascending sensory tracts (from nuclei grxllls and aJneib.Js, see p. 233, 326) decussate in the medialJlmfli$(UJ. The SGiitary tract carries the gustatDry fibers of
ctthe so/limy trod (not shown). The pymnldal t1oct ~gain appegrs as a mmpact structure at this lewl due ID the abten~ ofinter-

Is the nudaJs

spened nuclei and decuSSitlng flben.

Neu~YU~rurtomy - - '· BnJlnstwn

Nudeus IJ'
Sott.y

~~- =" Nudeusof

~

acauarynerw Medlallonglt:udlnal

I

c

Tecmsplnal

Medial

lRct

lemniscus

TniMWne teeaon }'Ust IM!Iowtfle middle aftfle medula

oblongftll Nuclll: The n~Jelel of the hypoglosnl, Vigus. and trlgemln..l nerves appear at this level. The Irregular outline of the Inferior olivary nucleus Is still just VIsible In the ventral medulla. The nuclei that relay signals &om the posterior funituluHhe nucleus cune;atuJ ;and nudeU$ gracilis-;ap·

Nudeus

CJnelb.ls~'

Sub:stllntfa

gelltfnos;a"""

\

pear prominently In the dorsal part of the section. Thetraru thatartse from theR nuclei dKUSsate in the medi;ll lemniscus (see above). 1hlctl: The ascending and descending trim correspond to those In the pn!llfoll!i diagrams. The rhomboid fossa, which Is the floor of the fourth vent:rlde. nas narrowed substantially at this lewl to become the central unal.

Filsdwlus

Nudeus glldls

gradlls

fasc!o.fus

I/

wnatus Sort.y

~tnct

Spln.llnucleusaf-......__"""

/'

!Jigemnalnerw

---------

-.....

t.adcuiiiS

- - - - - - - - Nucleusaf

~l)'nenot

emrat a rill

llrtkulu fonnrtlon

O!nt:.tlsympllt1~

A./7' J \

Postufarspnc.-

~larb'Xt

/

RubiO'Jilillil tnct Ararlor~niclal

llliCI

D TniMWne teeaon through tfle bwr medulla oblongata

The medulla oblongata~ continuous with the spinal cond ;at til~ level, sh~ng no distinct transition. Nuclei: The cranial nerve nudellllslble ill tills level are tile spln..l part of the trigeminal nerve and tile n~Jelell!i of tile acassory nerve. This section passes til rough tile caudal ends of the nuclei in the r&y sution of the posterlorfunkulus-the nude~~S aJneilt:Us and nucleus gracilis.

mtilose rn the pi'\MGus di;lgr;ams of tilis unit. The section passes til rough tile decussatlon Gfthe pyramids, and we an now distinguish the ;mterior pyr;~mldal tract (uncrossed) &om the lateral P')'ramldal tract {crossed; see p.338). CSF spaa!: This section passes through .a portion of tile antral canal, wflich is markedly smaller ilt til~ level tnan in C. It m;y even bto obliterated at some sites, but this his no clinical slgnlflcana.

1'rllct.t:The ascending and descending tracts correspolld

Neuroanatomy - - 7. CeniM#Ium

Cerebellum, External Structure

7.1

Mediin pert

}----,.,;:.:,= ,!,,!...--

~bel'-'

hl!ll'l'itphn

~gu~r~

lobule Slmplelobule

Anterior

l'l1ml!ry ftsu~

lobe

'\.

~?-""'

Supellars..,.,lun•r ~(""" lobule / '

.. c.ntrol lobule

Uwulo ofwnrls

c

Wlecul•

Tcnsll

Pledunde

oflocculus

238

NfuroGittltrJmy - - 7. Ceebellum

A lllolltl!d cerebellum • lnh!rior view, b supcsior view, c: ~ntC!rior view. The ~bellum has Ileal removed from !he posterior cranial foss~ ;md det
The «rebellum Is part of the mowr sylWm.lt an not Init!~ coruclous moYements by Itself but Is responsible for uncon.lldous coordination ;md fine control of muscle ictlons (see B. p. 244). C"lo:uly, !he cerebellar surf01ce presents a much finer arrangement of gyri ind sulci than the cz. rellrum, prVY!dlng in even greater elQ)inslon of Its surf.!« area. Exter· nally the cerebellum cxmslm of two large later;al m;asses. the Cl!l'fbfJ/or hemiSpheres, ;md 01 centril part ailed the 1'1!1'1111s (see a). Cerf!bf!lfar fis· sures further subdivide the cerebellum intD lobes. In particlllar: • The prfm;ary fissure separates the ;anterfor lobe of the urebellum frvm the posterior lobe (see b). • The posterol~ral fissure separ.rtes the posterior lobe of the cerellellum from the flocculonodular lobe (see B).

Olfler, le.ss important fissures have no cliniul orfunctionil signifiunce ~nd are nat described t!ere. Besides these ~~tomical divisions, the p~rts of tile cerebellum an ;also be distinguished according to phylogeMtk: ind fulldtollal crlterfi (see c; ;also B. p. 244}. The cerebellum Is connecb!!d m the brainsUm by tile three CJ!f1!6tllar pedundts (superior, middle, and Inferior, see c). tflroughwhfch ltsi!fferent ~nd efferenttracts entEr and leave the cerebellum. The supertor medullaryYelum stretthes between !he supertor cerebeUu pedundes and fonns part of the roof of the fourth ventricle (see c). The cerebellar mnsils protrude downward near !he mldllr~e on e..ch side. almost to the for~men m~num at the base of the skull (not shown). Increased lntr;acranlal pressure may a use the cerebellar tonsils m hem late lnm the foramen magnum, Impinging upon viti I anters in the brainstan ind posing a threat to life (see D, p. 189). f\ntlonlllly, the mnllal port of the cerebellum (red) Is distinguished from the 117tttmedfarl!part (pale red) and fotl!rof part (gray). This functional classll!catlon does not conform to the inatomlt.llly detlned lobar bcunclaries. Each of these parts pi'Gjects to a specific cerebellar nucleus (seep. 240).

>---:-+--

Po:m!rlor lobe

ofan!bellum

8 RlliltloniHpofthecerebellum to the brain stem Uft later~! vrew. The cerebellum overlies tile donal aspect of the pons. Only the middle cerebellar peduncle un be ldentltled In this external view. The cm&e/lop(Jn· lfn~ onglto Is clearly dlsplil)'ed. It has gi'Nt cllnlc.1l lmportince beause It rs the site where Cl!fl!bfi!Gpanl1nt trnglt tumats develop-most commonly ~coustfc n~romas (see D. p.149}.

• Archkerebellum

• Flocculonodular lobe

• Vestlbuloa!llbellum: malntenanm of equlllbllum

• Paleoa!DIIum

• AniBtorlobe af urebellum • Portions ofthe vermis • Medial portions af the postellor lobe

• Splnocerebellum: regulation of muscle tone

• Neocerebellum

• Lateral po111ons ofthe posterfor lobe

• Pontocerebellum (- mll!brocerebellum): skilled.,_ menls

239

Neuroai'H1tomy - - 1. ~lum

7.2

Cerebellum, Internal Structure

A The cerebellum, bt~~lnnem, •nd dleiiCI!ph;llon Mlds.ilgltt.ll section llfewed ftom lfle left side, displaying the internal structure of lfle cerebellum. The Interior of lfle anbellum b com· posed of whlll! I7IOfm' ;md Its extafor of !Jff1Y I7IOfm' (Cfl'l!l:lel/ar t:l:ll'!l!!l(. 'Whose layers ire shown iA D). Thiuection agair\ shows how the cerebellum abuts the fourth ventricle. In which ttle choroid plexus an be seen. The superior medulliry velum forms the IIPPf!' portion of the roof of the fourth w.ntride; lfle lingula is doM:iy apposed to Its dorsal surf.rce. The loww portion of the roof of ttle fourth ventricle Is lr1 contact Mth ttle cerebellar nodule. This section demonstrates h- the cerebellar cortex Is deeply folded Into folia (gyri, not lndlvldu· ally labeled). producing a t~llte outline of ttle white matter called ttle orbor 'ift!H! ("tree oflife•).

Ungula

·- r.r--:...---

Ha-l ftssun.

B Nucleloftflecerebellum

Section through the superior cerebellarpedun·

1\lach.fe

des(planeofsectlonshownlnA).IIfewedfrom behlfld. Deep within the cerebellirwhlte mat· lll!r are four p;alrs of nuclei ttlitcontaln most of the ~t neurons af the cerebellum: • • • •

fml!glal

Fistigial nucleus (green) Emboltform nucleus (blue) Globose nuclei (blue) Dentorte nlldeus (pink)

nudeus

The cortical regions hawe been color-coded to mmh their t:arget nuclei. The dentorte nu-

deus is the largest of the ce<ebdl;ar nudC!i and emnds Into the anbellar hemispheres. The cerebellar nuclei rece{ve projections from Purklnje cells In the cerebellar cortEx (see D). 1Mlile the ~t {ibt:n of the cerebellum c.ar1 be isslgned rather eislly to anitomlcal struclllres, Ulls Is not true of lfle afferent tlbers. Their sourcts .are examined on p. 244.

Embollfonn

nudeur.

- - - - , . . . --:r--Dent.1te nudeur.

C Cerebellar nudel and the regions of the axtex from wfllch they l't!GI!M prqecttons (see alsop. 238)

...t.. ofthe--..lerCDI'IDthltsmd-IIIID thenudeiU Denbll! nudeus

Lateral cerebellar nucleus

Lateral pert (lateral portions of the cerebellar hemispheres)

Embollform nucleus

Anterior lnll!rposltus nudeus

lnll!nnedlate pert (medial portiOns of the anbellarhemlspheres)

Clo~nuclei

Posterior inll!rpositus nucleus

lnll!nnediate pert (medial portions of the anbellar hemispheres)

F.mlglal nudaa

Medial anbellar nucleus

Median part (cerebellar wnnrs)

240

NfuroGittltrJmy - - 7. Ceebellum

Parallel flbers

D C«ebdlercortex The cerebellar cortex consists of three layers: • Molecular layer. outer layer. contains (XIr· aflel [Ibm. which are the axons of granule cells (blue) from the granular layer. They nun par~llel to the a!rehellarfaliHnd b!rmirla'le In the molecular layer. where they synapse Into the dendrites of the Purklnje cells. This layer .also contains .iiXDnS from the lnfe. rior olive and iU at«!S$01')' nuclei (dimbing /lbfrs) and a small number of Inhibitory lnterneurons (baslll!talld stl!l/are neurons). • PIJrkln}e layer: contains the cell bodies af Pudcin}! cells (purple). • Granular layer: contains mostlygiVmufeal/s (blue), as well as mossy and dfmblng fibers (green .ilnd pink, respecUve!y), and Golgr cells (not shown; the all types are viewed in

Molecularlayer {

... ! PurtilJe{

·~

~lllyoer

~~--{

F}.

'W...l' - - -

Neuronsrn den!at2nucleus

The white matter of the cerebellum Is located under tile granular layer. Nob!: The Purldnje cells lire the only efferent cells af the cerebellar cortex. They project to the cerebellar nuclei.

au

....

Gra...,le CElls ~Nbbry

lntemeurons Aftinnt mnl'll!dlom

,-------~-----------------+

-·-

IIIDS~Yflbers

Neurons of areblllarnuclll

Clmblngtlben

I

I

l'onli'lenuclel. spinal

Inferior

aH'd, nuclelofiiii!Silbular·

clive

ax:Nmrnerve E SynaptTcdi'GilbyoftheGI!rebelklm (after Biihr and frol$cher) The cerebellum comprises 10% of the mass of thebr.illn,butcontalnsuptoSOXofltsneurons. This enormous popcJiatiCin (cerebellar granule cells alone may number ln excess of 1OD bll· lion) Is composed of .il few cdl types arranged 1r1.a repetltl~ highly ordered array. This repetition of simple elements has led to tile deKrlptlon f1f the cerebellum as .ilrl Intricate syn· aptlc computer for motor coordlrliltlon. The basic cerebellar cll'lllltry Involves ~ ents including dimbing and mossy fibers. CJ(mblng {Ibm orlglrla'le from the Inferior ol· lv.lry complex and form multiple excitatory S)'rl.ilpses on the cell bodies .ilnd proximal dendritic tree of Purkinje cells (see D); collateral branches synapse In the (deep) cerebellar nu· del. Mossy~orlglrla'le In Ulew:rtfbular and por1t1ne nude! and tile spinal cord to form excitatory contad3 with grar1ule cells in synaptic complex.es called cerebellar glomeruli (see D); some branches excite local Inhibitory neurons,

F

PrfncTp;~l nauronnnd fltMrtypes In the cerebellar c:ortll!x

flben

Allons or neurons or the lmrlor allw and 113 assoc'lated nuclei

Mauyflben

Allons ar neurons or the pontine nudel,

armblng lhlllamus, red nucleus. nudelofiiii!Silbulll'mchlellrnerw. retlallar fannatlon

and colliltl!rllls also enter the cerebellar nuclei. The ax.ons of granule cells fonn parallel flben Ulatform excitatory synapses on the dendritic 1reesofPUrkln}ecells. ThePUrklnjec:ellslntum send their ax.ons mostly tD the cen!bellar nu· del (see I, above; also to vestibular nude!), where they make Inhibitory synapses. The fdentltle.s of some neurotransmitters In this pathway have been established: lacal inhibi· tory neurons, and Purldnje cells themselves, use gamma-amlnobutyrlc acid {GADA). while gr.ilnule cells employ gllltllmate.. Glutamate Is prob.ibly also inw!lll!d at mauy and dimbing fiber synapses. The prlndpal cerebellar cffer· ent axons arise from the cerebellar nudel. This drcultry combines direct activation (.ilfli!rent:s tD granule cells to Purkinje cells) and indired: Inhibition (afl'erents to Inhibitory lnterneurons to Purldnje cells). whkh may be Integrated rn a complex spatial pattern and tempor.ill sequence in the cen!bellar cortex and deep nu· del to provide lndlrec:t feedb.irl: control for motor coordln<~llan.

the spinal cord, and wstlbular nudel (pontocertbellar, splnaurebellar, and wstlbular tracts) Parallel fibers (set D)

Granule cells Purkinje cells

Allons or granule cells I~Urneurons of the cerebellar CDrtelc

The onl, effi!rent cells

or the cerebellarcortex; - r t an Inhibitory elfect

241

Neuroai'H1tomy - - 1.

7.3

~lum

Cerebellar Peduncles and Tracts

Anl8!arspln.,. an!Ottlar Inlet

A cerebellllrpedundes ;a left lateAI ¥lew wlth the

upper portion of the cerebellum and Iitterai portions of 1he pons removed. Th~ dls,seciSon, which nas bftn prep~red to ~~ fiber Jtrucwre, dearly sh~ 1he course of t:tle cerebellar tracts. The size of the cerebellilr pedundes, and t:tlus the mass of entzring and emerg· lng axons.ls substantial and reflem the ex· tenstve neural connections In the cerebel· lum (see p.241}. The cer1!1lellum requires these numerDus connections because it is an Integrating «nter far the ooordlnat!on of flne moveme!113.1n p;u1:IOJiar,lt c:ont.11ns and processes YeSt1bular and proprloce~ ttve alli!renu and It modulillli!S momr nudel In ather brain regions and In the spinal cord. The prfndpal alli!rent and efferent connections of the cerebellum .are re¥1ewed In B. b Left latl!ralview. Hen! the arebellum nas '-" wrply detached from Its peduncles to demonstr.tte t:tle complementary art surface of the peduncles on t:tle bralnstem (compare with 141:, p. 238).

- ---=:r--'kstlbuiO<:JXhlesu

--~-------l~

n~

peduncle

"'f-- lniellol'~~r peduncle

b

242

Mlddll!an!bellr

Neuroanatomy - - 7. Cerebellum

B Synopsis of the cerebellar peduncles and their tracts Tracts made up of afferent and efferent axons enter or leave the cerebellum through the cerebellar peduncles. The afferent axons originate in the spinal cord, vestibular organs, inferior olive and pons, while the

.......

Cerebel._po!dunde ...t constituent

efferent axons originate In the cerebellar nuclei (see p. 240). The representation of the body In the cerebellum, unlike In the cerebrum, Is Ipsilateral. Ascending cerebellar tracts thus cross (decussate) to the opposite side.

Origin••

Site oflemolnoltlon

Supnlor aebellior peduncle: CDntaim mostly efferent tracb from the cerebellar nuclei. Some tracb cross in the decussation of the superior peduncle, then divide into alksconding limb (to the pons) and an ascendii!IJ limb (to the midbr.Jin and thalamus).

Descendng parts (a)

Fastlglal and globose nuclei

Reticular formation and vestibular nuclei (projection Is mostly coiiiTalatm!l)

Ascending parts (e)

Dentate nucleus

Red nucleus and thalamus (both contrv/ateral)

Anterior splnocerebellartrild: (a)

Secondary neurons In lnternnediate gray matter,lumbosacr.~l spinal cord. Relays proprioc;eption (muscle spindles, tendon receptors, etc.) from dor..1root (spinal) ganglion cells, lower limb and trunk_ Fibers cross locally and then re-cross in tf1e pons to return to the Ipsilateral side.

Vermis and Intermediate part of anterior lobe of cerebellum (ipsil~l; terminates as mossy fibers)

IWddle care!NIIar pacl•ncl~ contains only afferent tracts. Pontocerebellar fibers (a)

Basal pontine nudel. Relaycerebnopontlne to pontocerebelilr projection (source of9~ ofaxons in middle peduncle)

Lateral regions of posterior and anterior lobes of cerebellum (contralotrral; terminate as mossy fibers; branches to contralateral dentate nudeus)

Inferior cerebellar ped•ncle: contains both afferent and efferenttnK:ts. Posterior spinocerebellar tract (a)

Posterior thoracic nucleus and thoracic spinal cord. Relays proprioception and cutaneous sensation from the lower limb. Contains large axons with high conduction ~~elotity.

Vermis and nearby anterior lobe of cerebellum, pyramid and nearby posterior lobe of cerebellum. (ipsihr~~ tenninates as mossy fibers)

Cuneocerelbellilrtract (a)

Nucleus cune;~tus and external cuneate nudeus. Relays proprioception (external cuneate nucleus) and cubneous sensation (nucleus cune.atus) from the upper limb, with fast transmission, functionally torYMponding to tf1e posterior spincxerebellar tr.~ct.

Posterior part of anterior lobe of cerebelh.•n (ipsila~l; terminates as mossy fibers).

Olivocerebellar tract (a)

Inferior olivary nuclear complex. lnferiorolr.e receives numerous Inputs from sensory and motor systems, Including a large contralateral projection from the cerelbellum Itself (dentate nucleus, see below).

Molecular layer of cerebellar cortex (controlalmll, terminates as dlmblng fibers)

Vestlbulocerebellar tract (a)

Semicircular canal (VI!Stlbular ganglion) and VI!Stlbular nuclei. Transmits balance and body position/motion Information either directly (VI!Stlbular axons via vestibulocochlear nerve [CN VIII], ipsilateral) or via synaptic relay in vestibular nuclei (bilofercll).

Nodule, flocculus, anterior lobe, and vermis of cerebellum (bllalmll, see left; terminates as mossy fibers)

Trigerninocerebellar fibers (•)

Trigeminal sensory nudei in the brainstem. Relay proprioception and cutaneous sensation from the

Rostral part of posterior lobe of cerebellum tenninate as mossy fibe")

(ipsihr~~

he.ad. Cerebello-olivary fibers (e)

Dentate nucleus

•subentries for constituent parts are classified as efferent (e) or afferent (a). ••1n the case of afferents, the type of afferent is listed along with the site oforlgln.

Inferior olive (controla~l)

243

NeurDGnatomy - - 7. Cerebellum

7.4

Cerebellum, Simplified Functional Anatomy and Lesions

Fastiglal nucleus L.,teral..:stlbular nucleus

SpiMIInpub (spinocermelum)

-.......

-

Medial descending systems

....... flGtcutlan

l.ater.ll descending systems

/

/

IIIPUb

Embollform nucleus Globose nucleus

(ponto-

cermelum)

Dentatr nucleus

Veotlloulior Inputs

--

Veotibular nuclei

(vestibulocerebellum)

-

Promotor oortex

- ,......,..,.. Pllunng.

..r.nc.,aculct-"Dr function

A Simplified functlonala1111tomy of d!e cerebellum requires feedback from muscle and tendon proprioceptors entering the (after Klinke and Silbernagl) cerebellum through spinocerebellar tracts. This "spinocerebellar" funcTwo-dimensional representation of the cerebellum. Left: afferent inputs tion utilizes more recently evolved paleocerebellar structures, the emto the cerebellar cortex; Right: paths of cerebellar (efferent) output. boliform and globose cerebellar nuclei, and modulates muscle activity through a "lateral motor system" that involves muscles in the extremThe coordination of motor activity by the cerebellum can be divided ities. The most recent evolutionary developments in the cerebellum into three broad categories corresponding to the areas responsible for the coordination: include the significant expansion of cerebral cortical projections via a • Maintenance of posture and balance ("vestibulocerebellum") relay in the pons, and a reciprocal massive cerebellar projection, through • Dynamic control of muscle tone under various loads ("spinocerethe dentate nucleus, back to the cerebral cortex via the thalamus. The bellum") neocerebellum thus sends information back to the cerebral cortex, • Integration of activity of various muscle groups during complex which controls some musculature directly through corticonuclear projections to lower motor neurons controlling the tongue and face (see tasks ("pontocerebellum") p. 232), and corticospinal projections to spinal motor neurons controlThese categories of cerebellar function require different types of afferent infomnation, and have different output (efferent) paths. Although ling the hands. This "pontocerebellar" pathway and function involves complex anticipatory activation of muscle groups to accept a load or afferent inputs and their corresponding tracts are not segregated by limit a motion, and so can be characterized in part as a "planning• or obvious anatomical boundaries in the cerebellum, there is a functional division that correlates with the evolution of the cerebellar structures "programming" function. Note: this simplified outline of cerebellar function does not take into ac(see B). The phylogenetically ancient part of the cerebellum (archicerecount the complexity of cerebellar contributions to a variety of other bellum) receives vestibular Input, projects to the fastlglal nucleus and lateral vestibular nucleus, and controls trunk musculature through a tasks. VIsual Inputs and oculomotor functions, specifically, have not "medial motor system" (see p. 282). Dynamic control of muscle tone been considered here. B Synopsis of cerebellar classifications and their relationships to motor deficits Some cerebellar lesions cause subtle cognitive deficits that cannot be explained simply as a loss of muscle coordination.

Vestlbulocerebellum

Ardllcerebellum

Flocculonodular lobe

• Truncal. stance ;ond Qilil ataxia • Vertigo

• Nystagmus

• Vomiting Spinocerebellum

Paleocerebellum

Anterior lobe, parts ofvenmls; Posterior lobe, medial parts

• Ataxia, chiefly affecting the lower limb • Oculomotor dysfunction • Speech disorder (;,synergy of speech muscles)

Pontocerebellum (- cerebrocerebelum)

Neocerebellum

Posterior lobe, hemispheres

• Dysmetria and hyp~metria

(positive reboood) •

ln~nllon lrl!mor

• Nystagmus

• Decreased muscle tone

244

Neuroanatomy - - 7. Cerebellum

C Cerebellar lesions Cerebellar lesions may remain clinically silent for some time because other brain regions can functionally compensate for them with reasonable effectiveness. Exceptions are direct lesions of the efferent cerebellar nuclei, which cannot be clinically compensated. Cerebellar symptoms:

Asynergy

Lack ofcoordination among different muscle groups, especially in the performance of fine movements.

Ataxia

Uncoordinated sequence of movements. Truncal ataxia (patient cannot sit quietly upright) is distinguished from stance and gait ataxia (impaired limb movements, such as an unsteady gait in inebriation). The patient stands with the legs spread apart and places his hand on the wall for stability (a).

Decreased muscle tone

Ipsilateral muscle weakness and rapid fatigability (asthenia).

Intention tremor

Involuntary, rhythmical wavering movement of the hand when a purposeful movement is attempted, as in the finger-nose test: normal test (b), test indicating a cerebellar lesion (c).

Rebound The patient, with eyes closed, Is told to move the amn phenomenon against a resistance from the examiner (d). When the examiner suddenly releases the amn, It forcefully "rebounds" toward the patient (hypermetrla).

d

245

8.1

Arteries of the Brain: Blood Supply and the Circle of Willis

A OftMI!w of the ;u'terial supply to the

E~----.--+---

brain Left lab!ral view. The parts of the brain in tbe

amrlor and middle cranial foJ$ae receive their blood supply from branches of Ute Internal carctfd.;u1e!y, whllepartsofthebraln lnthepos!l!rior cranial fo$5.1 are supplied by branchH of tfle Ye!Ubral and basilar arteries; the latter Is formed by the confl~~ence oftfle two Wltebral arteries. The carotid and basllar arteries are connected by a ViiStular ring called the cirde ofWIHis (see Cand D). In many cases thedrde ofWfllls allows for compensation« deaei5ed blood flow In one vessel Vlfth Increased "col!at· eral" blood flow through anotber vessel (im· portant In patients with stenotic lesions oftile afferent .ilrteries, see E).

....,.:!'j- -

Commanarotld

.. ~

part

246

-----,~~-+~ IR .

·-Z~r---~--

"¥--~--=~r-

SubdiMan ~rtuy

Middle

B 1Mfaur allitDmtcal dM!fons of the lntl!mill aroUd ar!I!I'J

~larttrY

zvgamatlc an:h (l)Qnllcial

ht!m.Jiarotld.art!ly, a!nllcialpart

Anterior view of the left inb!mal cai'Gtid artery. The internal cai'Gtid artery consists of fourtQpograpfllcally distinct parts between tfle carotid bifurcation (see A) and tfle point where It divides Into the an!l!rtor and middle cerebral .arteries. The parts (S4!par.rted In the flgure by white disks) are: (1) Cervical part (red): locatl!d In tfle lateral pharyngeal spKe. (2) Petrous part (yellow): loci!l!d In tbe carotid canal « tbe petrous bone. (3) CavemCILIS part (green): follows an 5-shaped cun~e in the~ sinus. (4) Cerebral part{purple): located In the chiasmatic c\s!l!m of the sub ;to rachnold space. Except for the cervical part which generally does not gilll! olfbrandles, ill tfle other parts of the lntanal carotid artay give off numerous branches (seep. 60). The ln!Tacran/Q/ parts of the ln!l!rnal carotid artery ue subdivided Into ftve segments (Cl-CS} based on clinical crltl!rla: • C1-C2: the supcadinoid segments,locab!d within the arebral part. C1 and C211e above tfle amrior dlnold process of tfle lesser'llfng of the sphe11old bone. • o-cs: the lnfi'acllnold segmerns,IDC.ilti!d Vlf!htn the cavemous stnus.

Neuroanatomy - - B. Blood Vessels ofthe Brtlin

Anll!rfarcommunlatlng _ _.,..~.,., ..ary

Ant.rlor a!n!bral.-t:l!l'y

~ Mlddlearebrala~ lramalcarolldartery

Ant8ior fnfl!rior

Anlerlar

Jj;.,+-----!!11-- communlc.~ltlg artery

~llrarll!ry

t.'ldcle an!lllllll..ary I ~Urn~I arolld..ary

Supe!ior an!bellr arll!ry

Pmtfnurteries Anttllot lllfnal CDnf\lence arll!ry oft!leslnuses

~lnfufor cer~beUmrtery

D V•rhnts oftfre cTrde of Willis (after Uppert and P;abst) The vascular conflt'ctions ~thin the drcle of Willis are SIJb)ect to~ slder<Jb!e varfatlon. As a rule, the segmental hypop!aslas shown here do not slgntftuntly .illtefthe notm.ill functions oftile .ilrteffal ring. ;a In most cases, the clrde of Willis Is formed by tile following ar1:ertes:

C Projection oUhe drde of Will II onto tile Hie oftfle skull Supertorlltew. Thetwovenebrilir1:el1esentertfleskullthroughthefo· r.. men magnum and unite behioo the clivus to form the unpain!d basi· lar ~rtery. This vessel then dMdn Into the two posterior cerebr~l <Jrterles (addllion<~l vessels thit nonnally contrfbute to the circle of Willis are

b c

shownlnD}.

Note: f.'!ch middle cerebr~l ;utery(MCA) is the din!ct continuation of the Internal motld artery on that side. Clots ejectl!d by tile left hwt will frequenUy embotrze to tile MCA t:emtory.

d

e f Q

the anterior. middle
Wol--- Cllmmon arolld artery

Slhd;Manartsy Bradllacephallc trunk

E Stenoses and ocd111lllns of.utedes supplyfng the bnln Athe!'O$derotlc lesions In older patients m;ay cause the narrowing (stl!no.sis) or complete obstruction (ocdusian} of .. rteries that supply the br~tn. Stenoses most commonly occur <Jt ar1:erlal bifurcations, ~Ad the sites of predilection <Jre shown. Isolated stenoses that devdop grad· ually may be compensated for by colla!ler.ill vessels. When stenoses OC· Cllt simultaneously at multiple sitJ!s, the cirde of Willi!. cannot compen· sate for the diminished blood supply. ~Ad anbr~l blood flow becomes Impaired (\'irylng degl'l!!e:S ofcerebr;lllschem!a, seep. 264). Note: The d.ilmage Is manifested cl!nlcally In the bralfl, but the cause Is located in the vessels that supply the brain. Because stenoses an! treat· <Jble, thefr dl
F Anatomkill bull of subd;M;an steal syndrome •subcliiVIan steal" usually results ti'om steno.s&s of the left SIJbcliiVIan ar· tefy (red cir
247

Neuroai'H1tomy - - B. Blood Vessels oftlu! Bl'tll1t

8.2

Arteries of the Cerebrum

~~ralarury,

Mlddeaerebr.al al'b!ry,

postalmmtlllatfng p;Jrt,

ruularp;~rt,

RS~mentP2

segmomM2 ,..P,,...------111!:==~~-- ~or«ommunbtlng

aury

Supjertar aerebellararury

Anll!riorlnfedar ---==--~~*"'~C+---lll ': aetsellar arury

A Artertes at tfle base of tfu~ linin The cen!bellum and tzmporallobe have been n!moved on the ll!ft side wdlspl;sythe courseohtte postErior cerebral artery. ThiJ 'Weww.as se· lecll!d because most ofthe arteries that supply the brain en!l!rtile cerebrum from Its basal .aspect. Note: the thr'ft principal ~rtzries of the cen!brum, the anterior, middle and poJ!I!rlor cerebr;ll ir!l!ries, 01rfse from different sources. The ante·

l1or and middle cerebral arterles .are branches of the Internal c.arotld artery, while the pc.sterior cen!bral arteries aretzrminal br.anches of the basller artery (see p. 246 f). The vertebral arteries, which fuse to form the b.astlar artery. distribute branches1»Ute spinal cord, brain stem•.arid

cerebellum (antelfor spinal artery, postzrtorsplnal.arterfes, superior cel'ebetlar artery, and anterior ~nd posterior inferior cerebetl~r arterin).

B Segmentr.lllfthe anterior, middle. and pod:l!ilior cel'l!bral artiKTes Segmentr.

Altl!ty

artsy

• Premmmunlallng part • Postcammunlcatlng part

• A1 • segment protdmal to the ant.ior cammunlcatlng artery • A2 • segment distal to the am.tlor communlatlng artery

Anterior untbral M'ocldle cerebral

• Sphenoidal p;1rt

• M I • firu hO
artsy(MCA)

• Insular part

• M2 • segment on the Insula

~roranbral

• Premmmunlallng part • Postcammunlcatlng part

• P1 • segment b~n the basilar altlery bifurcation and posterlorcommunlallng arury • P2 • segment b~n the posiBior cummunlcatlng artery and aniBior t.mporal branches

artsy

• Pl • lateral occipital artefy • P4 • medial oalpltal art8y

248

Neuroanatomy - - B. Blood Vessels ofthe Brtlin

Arttry of pre«ntral Arttry of sulaa Cl!ll!T.IIsulcw

Artlry of postantnlsulaa

c TennTnal branchesoftflemlddlecerebnl ll'tefY on the lltl!nl a!n!bral hem~

sphleft lall!ral view. Most of the blood YeSsels on the lateral surface of the br.il!n are ttrmlnal branches of the middle Wl!bral artery (MCA). Theyc
Prefronul lll't2ly

Mlddlt

tl!n'fiOral branch

• Inferior tamln ply the fTDntal and parietal lobe cortex Deeper structures supplied by these brindles are not shcrwn in the diagram (seep. 2501).

Anttrfor ttrnparal branch

D CGursecrfthemlddlea!ll"'!ffnnllrtl!fYTn the Interior of the lateral sulcu' left lateral view. On Its Wil'f to the li!teral surface of the cerebral hemisphere. the middle

Anter!ortempon~l

branch

Middle llemponl bra nell

I'G.It2ro rnec!lal frontal branch

Posterlartemponl brllncll

cerebr.al.ilrttryftrst courses on Ute b.ase of the br<~in; thi$ i$ the sphenoidal part of the MCA. It then continues through the lareral sulcus ilong the Insula, wltlch Is the sunlren portion of the cerebral coi1U. When thetempor.ill.and pariet
angular br.ancll

E Bnndles cftfle anl:l!rfDr 1nd posterfDr cercbn~l•rtertes on tfle medllll surfK~~:

cftflecerebrum Right cel'1!bral hemisphere VIewed fTDm the medial side. with the left cerebral hemisphere and bralrutem removed. The medial surf.lce of the brain Is supplied by branches of the an12rtor and posterior cel'1!bral arttrfes. Whne the crnterior alfb
249

Neuroai'H1tomy - - B. Blood Vessels of flu! Bl'tll1t

8.3

Arteries of the Cerebrum, Distribution

CcrpuJ

c;ollosum

Quci;Jtt-

nudeus

• Intimal capsule

Glabur. palldus

D D D

Antlerfar aerebral al'llery Mldclecerelr.ll .mry

Posts!aranbrlla118y

Seplllm pduddum

b

lhiRI'f!nlrlcle

A Distribution,.,_ of tile m.1ln Gl!fl!br.~l;~rtertes a Ultefal llfew of the left cerebr~l hemisphere, b medial view of the

near the cortical margin (red and pink). Thepostl!dorcerebril arterysu~ plies the ocdplbl pole and lower portions of the llempor~l lobe (blue}.

rightcetebr~l hemisphere. Mllrtofthe lateral surfaa! of the brain is sup·

Thea!nlr.llgray~ndwhitematterhaveacompii!Xbloodsupply(yl!llow)

plied by the middle cetebr;rl artery (green), whose branches ascend to the cortex from the depths of the Insula. lhe branches of the ontl!dor cerebral arwrysupplylhefrontlll pole ofthe brain and the cortical a reM

that Includes the anwrior d!oroldal arury. The anwrior and posterior cerebril artel1es supply most of the medial surfice of the briln.

250

Neuroanatomy - - B. Blood Vesstls ofthe Brtlin

Branchesm thalamlc nude! Bn~nch m globus pellldUJ Posteromedial C1!11!r.!lal'll!l'les

Ant>!folmral cmtr.ll artl!rtes Qentlc:UCIS!Nte artufes)

--~~~~~ · ~Jj~~~~,~~~- lnsularp;rt(M2) MlddleC4!11!bralartl!ry, , - --r-.;. . . .,...=ir--

MlddleClefl!bralartl!ry, ;phenoldalp;rt(Ml)

Aturior chot11idlllrlay

b

a

B Dlltlllutlon oftfle thnee m.~ln G!f'll!bral artertes In u - n e and coron~lsccttonJ ;a, b Coronal sections at the level of the mammillary bodies. c: Transverse section atU!e level of the Internal capsule. The intemal capsule. basal ganglia, and thalamus defM! most of their blocld supply from pai'omlng branches of the follei'Mng vesSEls at the base ofthe br.~ln: • Anterior choroidal artery (from the Internal arotld artery) • Antefolater.~l centr.ill arteries (lenuculostrlate artertes and mtate br.anches) with their temniool branches (from the middle cerebral artery) • Posteromedial central .ilrteries (from the postaforcerebral.ilrtefy) • Perforaung br.ilnches (from the posterior communlc;rtlng artery) Tbelnterr\alapsule,whlchlstraversedbythepyr.ilmldaltract.ilndother stnur:tiJres, recellles most of Its blood supply from the middle cerebr.al artery (ant:erior crus and genu) and from the anterior choroidal atn!ry (posterior crus). If these vessels become ocduded. the pyr.ilmldal tract and other structures will be Interrupted, auslr~g p.ir.illysls on the contral.ateral side of the body (stroke: centrlll p.iralysh, see con p. 265}.

J.7"-7=-+i7--

WcrnldGe a!Q

Middle--~~~~~~~~

cm!bral

artl!ry

• C

hnc:Uon;~l Cl!llters on the summ of tile cerebn1m

a Lateral lllew of the left cerebr.ill hemisphere. Regions supplied by br.anches of the middle cerebral artery ane shaded orange. Specific functions an be assigned to well-
on one side of the body suggests an ocduslon of the middle arebr.al .ilrtery. b Medial view of the right cen!!br.ll hemisphere. The •margin" of the sensorimotw cortex may be deprived of bl~d (dlnlcally m;mlfested by p.irilysls ind sensory dlsl:\lrbinces mainly iffecting the lowes limb) by .ilfl occlusion of the olltl!dorarebral.ilrtery. The VIsual cortex may lose its blood supply(C.ilwing blindness) through ar1 ocdusion of the pam/for cerebral artery.

251

Neuroai'H1tomy - - B. Blood Vessels oftlu! Bl'tll1t

8.4

Arteries of the Brainstem and Cerebellum

~~t----~~~~~~~~f~~j~. ~ I'M!M!

./Miiia:;-""';~.::::;;;'"'"'---"-,:~,.-*"--- ~ lnfufar anbo!Uar~rtl!ry

A Arterfesoftflebratnstem ;md

Cll!l'll!bellum • ll.as.ll view, b left l~teri!lview.

The bralnstem and cerdlellum are supplied by the basilar and cerdlellar arteries (see below). Because the basilar artery rs formed by tile union of tile tWII vertebr;l;arteries, blood supplied bythebi5llararteryls s;ald to come from the lll!l'tA!brobasllar CXl1l1pSex. The VI!!S$els that supply the lll'lllnlltem (~ephalon, pom, and medulla oblongat
2S2

ne<W t..mr.JI branches ---\!~..:::....,

::u.: ---"{;~--<~-~-

~~--¥--~~~---

Vtttebr;JI,rtl!ry Anb!t!cr

sphllarte-y

• Posterior Inferior certbellar artery (PICA), the largest branch of the vertebral artery. This vessel is usually referred to by its aaonym,PICA. • Alltafor lnfertor cerdlellar artery (AICA), the flrst major branch of!he basilar artery. • Superior cerebellar artery (SCA), the last major branch of the bisllar
Noa: tile labYrinthine artery which supplies

the Inner ear (see also D, p. 155} usually arises from the anterior inferior cerebellar artery, as pictured here, although It may also spring dl· rectly from tile basilar ;rrmy. Impaired blood flowlnthelabyrtnthlnearteryle.adstoar~acute

loss of hearing (sudden sensorineural hearir~g loss). frequently accomp;rnled by tinnitus (see D.p.149).

Neuroanatomy - - 8. Blood vas.ls oftM flrv1n

I Dllllflaltlon afthl! •111Bift af thRIInllllltlm ilnd anbl!lum tn mldMgltbl section (lfter IUhr and Fl'otsdl111) All of the brain sections st-1 here and below are supplied by the wrtebroiNsllar complex. The transverse sections ;n presentl!d In a c<~uclil-to-crmial Hria conespondin; to the di11:ction of the~ brobasl~r blood supply.

llsllor4~rtlry - - -

-orspln1llf1iltlylnd - - pa..medlln bmdiOS cfth.. ~.mty

-Wafor <2ftbelor .m.y

lnfator colllaJI

C Dlltrtbutfon of tt.urterfe. ofthe

mBI!nmphillan In llwiiWrse section Besides branches tram the superior cerebellar artery, the mesencephalon Is supplied chiefly by branches of the postertor cerebral artery and poneriw communieilting utery. IM!M!

- - - Midch

arobdar peduncle

D Dlttllbulfon oftt.ur11H!IS afthl! pans'-

t n - sec:tlon The pons derives 1b blood supply from short and long branches ofltle basilar artery.

=:=~ OIM! ---r--

r-

Vi9Jsnrrw

----,-='""=--- AIIIBiorspln•l•r11rJYind ' /

)

pal'llllodlon bnncha Cit' wrtobril•r11!JY

---~-··-

IE Distribution ofth• ar11H!IS afthe m...,ll• oblongltll Ill tl'ln-rse tedlan

The medulla oblongltills supplied bybrinches of the anttrfor spinal artery, and postErior lnfeorior cenebll!llar iilrtery (both arising from the Yl!t'Ubrlllrtery),aswellas the antertorlnfet1or cerebellar artery (first large branch of ltle basllarutery).

8.5

Dural Sinuses, Overview

A Rel;rdonshlp of the plindpill dul'il sln~~~es to the skull Oblique posterior VIew from the 11ght side (brain removed ;md tento·

Se.!detall In I

rium Windowed on the right side). The dural sinuses ~11! stiff-walledve· no us dlannds that recdve blo~ from the Internal and external cere· bra! veins, orbits. and alvarfa. and convey Itto the Internal jugular veins on bolh sides. With few exceptions (Inferior sagittal sinus, SUGight sl· nus), the w.alls of the dural sinuses ~re fotmed by both the periost~! and menlngeallayen of the dura matEr (see C. p. 189). The valwlen dural sinuses are lined lntanillly by endothelium and are el!Pilnded at some sites (partlcular1y In the superior sagittal sinus) to form •tatera! I!ICUnae• (see B). Th!!.K' C!JCIIilnsions contain the arachnoid V111i through which cerebrospinal fluid (CSF) Is absorbed Into the venous blood (see p. 194f). The system of dural sinuses Is dl\lfded Into ar1 upper group ;md a lower group: • Upper group: SIJper1or ;md Inferior sagittal sinuses. str;llght slr~us, occipibl sinus, transvene sinus, sigmoid sinus, and the conllue11ce of

the slr~uses.

• a.-r group: cavanous slr~us wlth ar1ter1or ;md posterior Intercavernous sinuses, sphe11opar1etat sinus. super1or and lnfenor petrosal sinuses. The upper and lower groups of dur~l slnwes cornmunlate'Wfth Ule venous plexuses of the ve.Ubral anal through the marginal sinus ;at the lr1letto the foramen magnum and through Ule basilar ple1Ws on the clivus (see C).

Tenta\lm oerebell lnumal )lgularl/eln

s~

51511ttihlnus

lolll!ral lacuna,.,.th arac:hlolllvtll (P.Jcchlcnlan granutauons)

Sinus

enclo1hdlum

....

B Stl\ldure of a cknl shlf, shown here f'orthe superforS~~glU:al Transvene section, occlptt.lllltew (detail from A). The sinus w.all Is composed of endothelium and tough, collagenous dural connectiVe tissue with a periosteal and meningeal layer. Betwl!en the two laycn is the si· nus lumen.

254

NM! the !;ate~;~ I I!ICUnae, wflere the a~<~Chnoid V111i open into the venous system. Superfldal cerebral veins (superior cerebral veins. brfdglr~g ~~elns. see pp. 186 iind 262) open lrlto the sinus lt3elf along 'Wflh diploic Yelns from the adjacent cranial bone. The sinus also recellles emissary veins-valveless "!!ins that esbblish connection$ ~mong the sinuses, the diploic velriS, and the extrilcranlal YelriS of the scalp.

Neuroanatomy - - B. Blood Vessels ofthe Brtlin

SUperior ophthalmiC \'Cin Sphenoparlet
Venouspl~of

fir.mencw;ale

l'elnlsq.la maw;

sinus ~or

Mickle menlngealwfn

lnll!rawmaus sinus

Superior

Basilar plexus

~I

!In us

In!I!!lor pe«ras.JJ

jugl.far for.rnen

snus

SIQmOid !In us

Ma!Vnal s'rna

Cftlt an!brlllwln Occipital

lnl!rlor

!In us

O!tl!tln~lvdns

TentOI!um Cl!febelll

lr.lnswn:e

sinus

Str.alght

!In us

Superior sagltllllslnus

Ccnftuen~ of

!he sinuses

C ou...l sinuses at tfu~ skU I bue

left and f19ht p;~rt.s beirlg intA!rmnnectA!d at the fnont and behind by an

Tr.~nsvene secdon at the lew! of the tentorium cerebelll. viewed from

anterior and a posterior Intercavernous sinus. Bdllnd the posterior lntefcaVemous sinus, on the clfvus,ls the baslli!r plexus. This plexus also contributes to the dr.llnige of the cavernous srnwo.

above (briln removed, olfllt.11 roof and tl!ntorlum windowed on the right side). The avemous srnwo fonns 01 ring around the sella turcru, Its

255

NeurDGnatomy - - B. Blood Vessels ofthe Brotn

8.6

Dural Sinuses: Tributaries and Accessory Draining Vessels Super1or sagittal sinus Deep middle cerebral vein

Basilar vein

A Dural sinus tributaries from the cerebral veins (after Rauber and Kopsch) Right lateral view. Venous blood collected deep within the brain drains to the dural si· nuses through superficial and deep cerebral veins (see p. 258). The red arrows in the dia· gram show the principal directions of venous blood flow in the major sinuses. Because of the numerous anastomoses, the isolated occlusion of even a complete sinus segment may produce no clinical symptoms.

lnl:!!mal

Anl:!!rlor

cerebr.~l vein

cerebr.lll vein

Ani:!! nor Greot cerebral vein

inte~UYemous

sinus Superficial middle cerebral vein

Confluence of the sinuses

sinus

+--- Jugular Supe~or bulb

Straight sinus Superior petrosal sinus Occipital emlssary..,ln

Confluence of the srnuses

t:avemous sinus Venous plexus of for.~men ovale

Condylar emissary vein

Vertebr.~l vein

External jugular vein

B Aca!ssorydralnage pathways of the dural sinuses Right lateral view. The dural sinuses have many accessory drainage pathways besides their principal drainage Into the two Internal jugular veins. The connections between the dural sinuses and extracranlal veins mainly serve to equalize pressure and regulate temperature. These anastomoses are of clinical Interest because their normal direction of blood flow may reverse (no venous valves), allowing blood from extracranlal veins to reflux Into the dural sinuses. This mechanism may give rise to sinus Infections that lead, In tum, to vascular occlusion (ve-

256

Internal jugularvein

nous sinus thrombasls). The most Important accessory drainage vessels Include the following: • Emissary veins (diploic and superior scalp veins), see C. • Superior ophthalmic vein (angular and facial veins). • Venous plexus of foramen ovale (pterygoid plexus, retromandibular vein). • Marginal sinus and basilar plexus (internal and external vertebral venous plexus), see C.

Neuroanatomy - - B. Blood Vessels ofthe Brtlin

S~Pttal

suture

\ Partetal - -----:,-------;iVJ

em'lwlrywn

~---~r---------~~--~~r

sagltbll sinus

umbdald ---------:~. s~re

---~------~~-----~---~~~ ofthulruses

E~~----

Ocdpltll

Slgnold

sinus

em'lwlrywn

~~--111-d

emtss.1ryw1n

Venousplf!lOisarour>d ---'.-~

thtlinmenmagnum (marginal sinus) "'--¥-~-~----

O<xlpltll tOnctyle

~-~---

ht2mol ).!gular win

£xt8T!alwrll!br.tl wnous plexus

--""""'1~----'t­

C Oc:dpltal emlaatyveh Emissary veins esubllsh a direct contleCtfor1 betweer1 the lntraaanlal dural sinuses and extracranial 111!in.s. They rur1 thrcUJgh small aanial openings such as the p;~r!et
meningitis.

257

Neuroai'H1tomy - - B. Blood Vessels oftlu! Bl'tll1t

8.7

Veins of the Brain: Superficial and Deep Veins

Becau~theveln$ofthebr~lndonotrun p;~ralleltotheartaiH,marted

dllferenc:es ire noted betv.'Hn the regions of arterfil supply and venous drainage. While ill of the cerellralir1:el1es enter the brain at Its bOise. venous blood is driined from the entire surfilce of the br.airl, induding the bOise. ~nd also from the Interior of the br.alr1 by two groups of vein$: the suJifl1lclal m'fblul veins 01nd the detp cmbrol llel'ns. The superficial veins

drain blood from the cerebral cortex (vla cortl~l veins) and white mattel' (Yla medulliry veins) directly Into the dural slnll!es. The deep velfiS drain blood from the deeper portions of the wfllte matter, baSil ganglia, corpus callosum, and diencephalon irlto the great c:etebril win, which entm the straight sinus. The two venous reglo1u (tho~ of the superflclalirld deep Ydns)ire lntefconnected by numerous lntric:erebralinastomoses (see D).

~~ar----~~~~~~~~~~

anntamotlc:wn (ofll'alard) ~per'lar

SUperftct.ll m16de Cl!l'ebralwln

--if~~~..:........;:~.,#

sinus

lnfer!ar

• Antufarwnof

s¢Jmptlklddum

1Nia mastrla1e

SU~ar

wn

aerebr.llwru

sag!Ual

anastomatlc

wl'l(oflolb~

5~

~lttahfnus

Tr~

s'rna

A Supet'fidlol vel._ of the br•Tn (superfldlol a:t"eb1111 velnJ) Left lmril Ylew (a) and medial Ylew(b). ;a, b The supertldal c:erebril veins driln blood from the short cortl~l lltlns <md long medullary vetns In the wflllle matter (see D) Into Ute du· ral sinuses. (The deep Cl!n!!br.al wins are described in C. p. 261.) Their course Is extremely variable, ~nd velfiS In the subir~clmold sp;~cedo not follow irtei1H, gyri, or sulci. Consequently, only Ute most lmportint of Utese VI!S$els 01re named here..

258

Jllrt before tefminating in the dural sinuses. the veins ~ the subi'rachnold sp;~ce ind run a short subdural course between the duri mater irld iracltnold. These short subdural venous segments ire ~lied brldg· 1ng lll!lns. The bridging veins hill/e gneit clinical lmportilnce because they may be ruptlJred by head tr~uma, resulting in a subdur~l hem~ to mil(~ p. 262).

Neuroanatomy - - 8. Blood vas.ls oftM flrv1n

I ...lontlllri!IMIII by tlw IUpetflclill

al'lbl'lllwtns Left lmnl view. ~ view of the medial surfaa of ttle right hemisphere, c !Nul vt-. The wins on the lateral surface of the brain are dmslfled by their direction of drainage as - . ling (draining Into the superior sagltbl sinus) or descending (draining Into the transwne sinus). The supertlml middle cerebral vein drains into both the t-rnous and triiiMvene sinuses (see A. p. 2S4).

il

• D

Super11dal asandlng

D

s...,..tctolmlddleanbrolw"

c

ardJ~IveiM

D

Billllarwln

lnlllf~.------ Decpmlddt

peduna.ior

win

ardl111lveln

lnr.rtor --':--l--,fchoroldal • "

ee...trol peduncle

qJ:;,..--

~~.--....!;~. .

Intimal

ardl111lveln

l'astlrtor ---'...,_~­ wnou,s Clllllluenat

C ...1Al'lllllwl WIIIO. . syst:ml The basal cerebral YMous system drains blood from both superfic:iel and deep cerebr~l veins. A venous drde formed by the basilar veins (of RDsenttlal, see below) olsts at the base of the br;aln, analogous wthe uterf;al drde of Willis. The biiiiSIIir W!ln Is formed In the anterior perfor~te substance by the union of the anterior cerebr;al and deep middle cerebral veins. Following the course af the optic tract. the basilar vein runs post2rlorty around the cerebr;ll pedundund uni!Rs 'ftfth the basll;arwfn from the opposite side on the donal aspect of the mesenceph;alon. The ~ Internal cerebr;al wins also termlna at this wnous junction, the postalor venous confluence. This junction glw:s r1se to ttle midline great cerebral vein. whldh enters thestralghUinus. The biiiiSibrveln m:elves tributaries fTum deep brain regions In Its course (e.g., wins from the ttl~l~mus ~nd hypothalamus. choroid plexus of the inferior hom, etc.). Thetwoanterlorcerebral Vll!lns are lnteroonnected by the anterfor communicating vein, cnllting 1 closed, rin~tshaped drainage system.

Longltullln;ol wind caud~ nuc:MUI

Tl'onM!f'SI! veiM Df

oudmnudeuJ Olan>llillw"

nt.rnol anbr.~l ...n

-"•- - Me4ullilryvdn ~~4b~~~~~--~~-¥BnDfomrum semkMIIe

Supl!fftd.l midcl~ ardl111l ...n

T..mlnal wn Decpmldd~

loledlal•~or

«"'bnlwln

lent!tular'Wlhs

D Anlltomot" betwMn the superftclll ;md d"P mrebr1l veins Trans~e section thnlUgh the left hemisphere. anterior view. The superftdal cenebr;al wins communlate with ttle deet~ cerebril veins through the aniiiJtomoses ,J,-n here (see p. 260). F1ow reverSill (double 1rrows) rnayoa:urln the boundary:r.anes between two terrltDria.

259

Neuroai'H1tomy - - B. Blood Vessels offlu! Bl'tll1t

8.8

Veins of the Brainstem and Cerebellum: Deep Veins

A Deepa!n!bralvtl:nt Mult!planar tr~nm~rse section (CXlmblnlng multiple tr.mwel'5e planes) with a superior 11tew ofUte opened late!'ill ventricles. The tem· poral and occipital lobes and tentorium cerebeUI have been remOftd on Ute left side to demonstr~te Ute upper surfa~ of Ute cerebellum ilnd !he supelfor cerebellilr veins. On tne lateral Wills of tne anterior homs of both li!ter.!l ventrlclu. !he superior thalamostrlate vein runs tow.lrd the lnterventrlcular foramen In the grocM! between the thalam.a and c;~ud~te nucleus. After receiving tne anterior vein of Ute septum pelluddum and the superior choroidal vdn, It forms Ute Internal cerebral vein and passes Utrough Ute Interventricular foramen along the roof of the diencephalon tuward tne quadrigeminal plate. which CQn· talns the superior and Inferior CXlllla.tll. There It unites with the Internal cerebral vein of Ute opposite side, and the basal ~ns to fonm Ute posterlor venous confluen~. which gives rise to Ute great cerebral vein.

Anterfarw)l of - --':-- --'rl "PP:Um peluddum ~--~r--Supe~~lam~

strlateYI!In ~~~-_,~~~-~~--Supe~

choraldalv.!ln

~----:-:-- l.all!r<~lwinof

lirl:l!ralwnlr!de ~~---"=--....'---Grut

<min! vein Med:lalw\1 of

lall!ralventrlde

--...L..---7----:-- - - Slr.l'ghtslnus :.lf'>-...£....-

--";,-----,-:'--- -


tile sinuses

~=:---- Superior

/ l ,._JIIt,..

(Medal) Inferior

CanflU~r~C~eof

arebelarwn

lhe,rnUIH

I C.rabellarwlns Posterlorvlew. Uke Ute oUter wins of the brain, Ute cerebellar veins are dlstl!buted Independently of the cerebellar artl!rtes.. urger trunks aou over gyri and sulci, running mainly intne sagittal direction. Amedfol and a latm/1 group c;~n be distinguished based on lhelr gross topographic;~! anatomy. ThemedlalgrocJpofcerebellarvelnsdralnsUtewnnfsilndad· jacent portions of the cerebellar l)emlsphen!l (precentral velD, supel'for

260

pelrOSals_,ur.

lrmnorwln olwiT!IIs

;md Inferior wins oftfte YEI!T11s) ;md Ute medial portions oftne superior and Inferior cerebellar veins. The lat!!ralgroup (petrosal vein and lmrill portions of Ute superior and Inferior cerebellarvel'ns) dr~lns most of the two ttl1!beli;lr hemispheres. All of the ~bellar veins ana.Jtomose with Ofle anoUter. ti)elr o~ Is exduslvely lnfrarentorfal O.e., below the tentorium cerebelll).

Neuroanatomy - - B. Blood Vessels ofthe Brtlin

Atile'Omediill ll\ilitomo:sb

lntltrpeduncular vefns

Antmllatenl a nast11 mosl$

Ponlom~

CII!Phlllcwln

Trlgenmlnemo

SUperior wnnlllnw'b

An!Jeromedllln pontine win

c lll!glon dn~tned bytfle deep G!l't!bnl vclnJ Coronal section. Three pr1nclpal venous segments Coiln be fdenUfted In each hemisphere:

• Thalamo5trlateveln • lntem.al cen!bral vein • 8il$0llveln The ~gion dr;ined by the deep «rebr~l veins encompanes large portions of lfle base of the cerebrum, the ba~l ganglia, the Internal Coilp· sule, the choroid plexuses of the liltl!rlll and third ventricles, the corpus Coilllosum, and por· tlons of the diencephalon and mesen«pha· Ion.

SUperior Cfi'Ebeltlrwln$

TtanM!ne

An!Jenllltl!tlll pontine vein

pontfnewll'il

'lt.lt\S\'I!I'V

mecllllaryw!ns

• Postelor

choroidal vein

D

VetnJofthebn~tnmm

• Anterior view of the brainstem in situ (the cerebellum and part oftfteocdpltallobe hawoe been removed on the left side). b l'o.itenor view of the isolatl!d brainstem with the cere·

bellum removed. The velns of the bralnstem ire a continuation of the veln.s of the spinal cord .md connect them with the ba~l veins of the brain. As en the spinal cord, the veins on the lOWEr part of the bralnstem form a veno~JS plexus consist· lng of a powerfully developed klngttudfnal system and a more branched lnrnM!IW system. The veins of the medulla obion gat!, pons, and cerebellum make up the lnfratentorlal Yenous system. VarfoiiS anastomoses (e.g.,llntenlrne· dial and lateral) exist at the boundarybet:ween the fnf'r;a- and suprmntllrial systems.

r•~~~--

l'o:stltrolmllll - -llr-\ meduii;Jrywln

C..udalarebellar peduncular vein

., ...~,..i~F-- Ve'b of Cl!n!bel~ meduhryds11em

L .:t-lHif-- - Posteromectan b

meduhrywln

261

NeurDGnatomy - - B. Blood Vessels ofthe Brotn

8.9

Blood Vessels of the Brain: Intracranial Hemorrhage

Intracranial hemorrhages may be extracerebral (see A) or intracerebral (seeq.

A Extracerebl'ill hemoiThages E.xtracerebral hemorrhages are defined as bleeding between the calvaria and brain. Because the bony calvaria is immobile, the developing hematoma exerts pressure on the soft brain. Depending on the source of the hemorrhage (arterial or venous), this may produce a rapidly or slowly developing incompressible mass with a rise of intracranial pressure that may damage not only the brain tissue at the bleeding site but also in more remote brain areas. Three types of intracranial hemorrhage can be distinguished based on their relationship to the dura mater: a Epldul'ill hematoma (epidural = above the dura). This type generally develops after a head Injury Involving a skull fracture. The bleedIng most commonly occurs from a ruptured middle meningeal artery (due to the close proximity of the middle meningeal artery to the calvaria, a sharp bone fragment may lacerate the artery). The hematoma forms between the calvaria and the periosteal layer of the dura mater. Pressure from the hematoma separates the dura from the calvaria and displaces the brain. Typically there Is an Initial transient loss of consciousness caused by the Impact, followed 1-5 hours later by a second decline In the level of consciousness, this time due to compression of the brain by the arterial hemorrhage. The Interval between the first and second loss of consciousness Is called the lucid lntel\101 (occurs In approximately 3o-40% of all epidural hematomas). Detection of the hemorrhage (CT scanning of the head) and prompt evacuation of the hematoma are life-saving. b Subdul'ill hematoma (subdural • below the dura). Trauma to the head causes the rupture of a bridging vein (seep. 254) that bleeds between the dura mater and arachnoid. The bleeding occurs Into a potential "subdural space," which exists only when extravasated blood has dissected the arachnoid membrane from the dura (the spaces are described In C, p. 191 ). Because the bleeding source Is venous, the Increased Intracranial pressure and mass effect develop more slowly than with an arterial epidural hemorrhage. Consequently, a subdural hematoma may develop chronically over a period of weeks, even after a relatively mild head injury. c Subarachnoid hemoiThage is an arterial bleed caused by the rupture of an aneurysm (abnormal outpouching) of an artery at the base of the brain (see B).lt is typically caused by a brief, sudden rise in blood pressure, like that produced by a sudden rise of intra-abdominal pressure (straining at stool or urine, lifting a heavy object, etc.). Because the hemorrhage is into the CSF-filled subarachnoid space, blood can be detected in the cerebrospinal fluid by means of lumbar puncture. The cardinal symptom of a subarachnoid hemorrhage is a sudden, excruciating headache accompanied by a stiff neck caused by meningeal irritation.

Epidural '-natoma

a

B~dglng vern

Superior ..gm:.l sinus

--...~=--

Sul>ar.llchnoid

space

b

Ruptured aneurysm of an arb!ry ill the base of the br.~in

Subarachnoid space

Dura miller

262

Inferior ..grttal sinus

Sub.lrachnold homorrllag•

NeuroamJtomy - - 8. Blood Vessels of the Brain

Ante~ or

Internal carotid artery

B Sites of berry aneurysms at the base of the brain (after Bahr and Frotscher) The rupture of congenital or acquired arterial aneurysms at the base of the brain is the most frequent cause of subarachnoid hemorrhage and accounts for approximately 5 !1: of all strokes. These are abnormal saccular dilations of the circle of Willis and are especially common at the site of branching. When one of these thin-walled aneurysms ruptures, arte· rial blood escapes into the subarachnoid space. The most common site is the junction between the anterior cerebral and anterior communicat· ing arteries (1 ): the second most likely site is the branching ofthe poste· rior communicating artery from the internal carotid artery (2).

Corpus callosum

Thalamus

Caudate nucleus

Hypertensive ---4~~~~--l-J hemorrhage in the region of the

basal ganglia

J:..r#-:ll....+-...3>..-+--

lentlculostrtate arte~es

Globus

pallidus

C lntr.lcerebral hemorThage

Coronal section at the level of the thalamus. Unlike the Intracranial exr:rocerebrol hemorrflages described above, lntrocerebrol hemorrhage occurs when damaged arteries bleed directly Into the substDnce of the broln. This distinction Is of very great cllnlcallmportance because extracerebral hemorrhages can be controlled by surgical hemostasis of the bleeding vessel, whereas Intracerebral hemorrhages cannot. The most frequent cause of Intracerebral hemorrhage (hemorrhagic stroke) Is high blood pressure. Because the soft brain tissue offers very little resistance, a large hematoma may form within the brain, The most common sources of Intracerebral bleeding are specific branches of the mid-

die cerebral artery-the lenticulostriate arteries pictured here (known also as the "stroke arteries"). The hemorrhage causes a cerebral lnfanctlon In the region of the Internal capsule, one effect of which Is to disrupt the pyramidal tract, which passes through the capsule (see E, p. 377). The loss of pyramidal tract function below the lesion Is manifested clinically by spastic paralysis of the limbs on the side of the body opposite to the Injury (the pyramidal tracts cross below the level of the lesion). The hemorrhage Is not always massive, and smaller bleeds may occur In the territories of the three main cerebral arteries, producing a typical clinical presentation.

263

Neuroai'H1tomy - - B. Blood Vessels of flu! Bl'tll1t

8.10

Blood Vessels of the Brain: Cerebrovascular Disease

artey

t

Cllrolldoc:dlollfon {llemoctjn;lrricdlstlnbance) Cllrolld bllin::ltlon

--"""'l"-----

A lftquent nuses ofGI!ftbi'VIIilliiiQIIar diiNse (aftef Mumen!haler) Disturbances of cerebral blood flow tf!at deprl\le tf!e br.illn of oxygen (cerebral iKhemia) .ilre the mort frequent cause of centril neurologial defldts. The most safous complication Is SU"oke: tf!e\'ist majority of all strokes are caused by cerebral Ischemic d~. Stroki! has become tf!e tf!lrd leading eo~ta~e of de.iltf! In westl!rn lndustrfalill!d countries (approxim;ately 700.000 strolaes occur in the United Sti!tes each ~r}. Cerebral Ischemia Is aused by a prolonged diminution or lntemuptlon of blood flow ;md lnwlltes the dlstrllxlt:lon orea G{ the ln!l!lnal aH'OtJd arwy In up 1:1> 90% of cases. Much less commonly, cerebrlllischemlllis aused by lin obstructi~n of venoll$ outflow due 1:1> cerebral venous thrombinis (HIC!

264

Tlu"(lmbotlc~l inleft~m

8). A decrease of ar1:erial blood flow In the arotld system most commonly results trom .ilrl embolic or local tf!rombotlc occlusion. Most emboli origimte from Jtheromati>UJiuions at the c;~rotid bifurcation (arterioartErial emboli) «ti"om the eJCpulslon of thrombotic m;ater1al ti"om the left ventr1de {ardlac emboli). Blood does (tf!rombl} may be dislodged from the heart~ .a result of \'ilYUillrdlsease or .atrial flbrtlla11or1. This produces emboli that may be anied by the bloodstream 1:1> the brain. where they may cause U!e functional ocduslor1 of an artEry supplying tf1e brain. The most common ex.1mple of tf!ls Involves all of the dlstrtbutfon region of the middle cer1!1lralli1Ury, 'Wfllch Is .il direct continu;ation oftf!e internal arotid artl!ry.

NeuroamJtomy - - 8. Blood Vessels of the Brain

b

B Cerebral venous thrombosis Coronal section, anterior view. The cerebral ~ins, like the cerebral arter· ies, se~ specific territories (see pp. 258 and 260}. Though much less common than decreased arterial How, the obstruction of~nous outflow is an important potential cause of ischemia and infarction. With a thrombotic occlusion, for example, the quantity of blood and thus the venous pressure are increased in the tributary region of the occluded ~in. This causes a drop in the capillary pressure gradient, with an increased ex· travasation of Huid from the capillary bed into the brain tissue (edema}. There is a concomitant reduction of arterial inHow into the affEcted re· gion, depriving it of oxygen. The occlusion of specific cerebral ~ins (e.g., due to cerebral ~nous thrombosis} leads to brain infarctions at characteristic locations: a SUperior a!rebral Rlns: Thrombosis and Infarction In the areas drained by the:

An~rlor

cerebral artEry

t.lddle cerebral artEry

Hemlp.oresls (with or without hem!sensory delleIt}

Hemlp.oresls (with or without hemlsensory delleIt} mainly affecting

Bladder dysfunction

Aphasia

theiM1Tiand face(Wemlc~

Mann type)

Hem!sensory losses

Hemianopia

• Medial superior cerebral veins (right, symproms: contralateral lower limb weakness); • Posterior superior cerebral veins (left, symptoms: contralateral hemiparesis). Motor aphasia occurs if the infarction involves the motor speech center in the dominant hemisphere. b Inferior a!nebral veins: Thrombosis of the right Inferior cerebral veins leads to Infarction of the right temporal lobe (symptoms: sensory aphasia, contralateral hemianopia}. c Internal cerebral veins: Bilateral thrombosis leads to a symmetrical infarction affEcting the thalamus and basal ganglia. This is character· ized by a rapid deterioration of consciousness ranging to coma. Because the dural sinuses have extensive anastomoses, a limited occlusion affEcting part of a sinus often does not cause pronounced clinical symptoms, unlike the venous thromboses described here (seep. 256).

C Cardinal symptoms ofoc:clusion ofthethne• 11111ln cerebral arbl!rles (after Masuhr and Neumann} When the anterior, middle or posterior cerebral artl!ry becomes occluded, characteristic functional deficits occur in the oxygen-deprived brain areas supplied by the occluded vessel (see p. 250). In many cases the affEcted artery can be identified based on the associated neurological deficit: • Bladder weakness (cortical bladder center) and paralysis of the lower limb (hemiplegia with or without hemisensory deficit, predominantly affecting the leg) on the side opposite the occlusion (see motor and sensory homunculi, pp. 329 and 339) indicate an infarction in theter· ritory of the anterior cerebral arbl!ry. • Contralateral hemiplegia affEcting the arm and face more than the leg indicates an infarction in the territory of the middle cerebral artery. If the dominant hemisphere is affected, aphasia also occurs (the patient cannot name objects, for example}. • Visual disturbances affEcting the contralateral visual tleld (hemi· anopia) may signify an infarction in the territory of the posterior cerebral artery, because the structures supplied by this artery in· elude the visual cortex in the calcarine sulcus of the occipital lobe. If branches to the thalamus are also affected, the patient may also ex· hi bit a contralateral hemisensorydeficit because the affErent sensory fibers have already crossed below the thalamus. The extent of the Infarction depends partly on whether the occlusion Is proximal or distal. Generally a proximal occlusion will cause a much more extensive Infarction than a distal occlusion. MCA Infarctions are the most common because the middle cerebral artery Is essentially a dl· rect continuation of the Internal carotid artery.

265

Neurot1natomy - - .9. Spinal Cord

9.1

Spinal Cord, Segmental Organization

IIDDfplm

IIDDfplm

Alarpw Alor pllll!

Zoneuf

autonomic nourans

•

Zoned ai!Dnomk noui'IIIN

White-

....,plalll

Basal pllll!

---:1--t-- - Antlrtorhom

Floor plalll

R-pllll!

'--:::,..c..---- c.rtnl anol

Ill

A Dewlapment of the lpln1l Clll'd Transve~W sectiDn. wpalor view.

Eilr1y neural tube, lllntmnedlite sage, c: idult spinal cord. The spinal mrd dMclps from the neural tube:

il

• PDsteJtor hom: dewlaps from the posb!rlor part of the neural l.\lbe (the olor plate). It contains the afferent (senSOIY) neurons. • AntetTor hom; dev.!lops from the anterior P'rt Df the neur;~l t\Jbe (the bosol plcn). lt contains the efferent (motxlr) neurons. • Lillleriil calwnn: develops from tile lnll!rwnlng mne. Present only In the tharacic, lumbar, and sur,lregions of the mrd, it contains the autDnomk(sympathetfc and parasynnp;11thetk) neurons. (Its longltu· dlnal distribution Is shown In C, p. 283.)

~~~~~~--t--~~hom

c

Neurons dD not develop from the raDf or flDOr platu. Viewing the spinal cord In transverse section, we see that It mnslm of gray !Nitter that Is a rnnged about the central canal and Is surrounded by whim mollttl!r. The ti'IY JMtter contains the all bodies of neurons while the whb JMtter consists of nerve fibers (iiXDils). Note: alfOns that hive the samefunctlon are collected Into bundles ailed ttvds. Tracts that tl!rmlnate In the brain are called asandlng, o(ferent or at~SOI)' tracts, while tracts that pass from the brain int:D the spinal cord ~re c.alled descending, ~tor mof1Jr tram.

Spiral

Dorulroodets

Plglo

Merlngul branch

Splonchnk

n..-

_L_,

I 5trudure of ••ptn.l card Mgment

Two main organization~ I principles are observed in the spinal cord: 1. Fundfa1111l orglllll.lltiDII w1t~11 • .egmellt (viewed In .a transverse section Df the spinal mrd). In each spinal cord segment. the cr/fetmt dors~l rootlets enter the back of the cord while the t/ffmrt -vartro1l rootlets emerge from the front of the cord. The rooCfets In each set mm brne to form the dorsal (posUrlor) and ventral (anterior) roots. Each dors~land venlnll raDt fuM:s to form a mixed ,mcrc-·which carries both sensory 1 nd motor fl~. Shortly after the fusion of Its two raats, the spiN I nerve diVIdes Into vartous branches. 2. TapagraphiiCII arpnlulbl of the ugmenb (viewed in a longitudinal sediDn of the spiN Icord). The spiN Icord consists of a wrtlcal sertes of31 segments (2eC), e.~d't ofwhld't lnnerwtes a speclflcarea In the trunk ;md limbs.

C Splnll card 11nd tpl1111l ,.IIIII• In 111tu Postufor view with the lam lm1r ard'tes of the vertebral bodies removed.

The longltudiNI growtn of the spinal cord lags behind that of the bony vertzbral column. As a result, the l~r end of the spinal mnd In the ~dult lies at app~U~
266

T8

T6

T4

ss

{_C6 -l \

_·1_,7

E Stmpllfl'ed schematic: rtpresentlltfon of tfle segment.! rnnerv.UOn of the tldn

(after Mumenthaler) Dlstrfbu!Son of Ute denmatomes on the body. Sensory Innervation of Ute skin correlates With the sensory roots of the spinal nerves In D. Every spinal cord segmem (except for C1, see below) Innervates a particular skin .arN (• dermatome). From a clinic.al standpoint, it is im· pomnt to know the pA!dse correlation qfder·

Vel'llllrllbcNir

Spin_,_

l~r ma~gln ofC6.

C&

TS TIO

T4

T12

L3

Tll

T9 T11

Sl

T12

T12

Splllll mnl111ment C8 T&

b D Splllll mrd segments and vertebral bodies In die adult ;a Mlcb;iglttal section. viewed from the right side. The spinal cord an bedtvlded Into four major regions: cervical cord (C. pink); Uloracic cord {T, blue); lumbar cord (1.., green); and sacral cord (S. yellow). The spinal cord segments are numbered according to the exit point of their associated nerves and do not necess.arily correlate numerically with the nearest skeletal elanent (seeb). The spinal cord generally terminates at the lew! of the L1 vertebral body, and the region be·

matomu With spinal cord segments so !hat the level of a spinal cord lesion c.an be determined bil$t'd on the location of the affected dermatome. For example. a le.slon of the CS spinal nerve root Is characterill!d by a loss af sensillton on the ulnar (small·flnger) side of the hand. Nob!: There Is no Cl dermatome because the first spinal nerve is purely motDr.

superior margin of c 7

low tni:s is knclwn ;as the t:IIIJ
tebral bodies wflen assusing injuries to the Ye!Ubril column (e.g .. spinal fr.lctl.lre and cord lesions, see p. 357). The parts In the table are only ~pproxlmatlon.s and may differ slightly in indiYidu~l c.;t~. ~there are only seven cervlc.al Ye!Ubra (C1-C7), but elght p;tlrs of cervlc.al nerYes (Cl-C&).

2fi1

9.2

Spinal Cord, Organization of Spinal Cord Segments

Post2flct

a.lumn

Anltrfar -~-­ fUniCYius

A Grq ~nd Yllf1lte rmttar of thupln;ll cord Three-dimensional represent.ttlon, oblique anterior 1lfew from upper ltft. • Gr;~y matb!r, b white m~ttet'. ThiJ tilree-dlmemlonal view shows how the gray matter Is dtvlded Into ttlree columns: • Antl!f'larcolumn (anterior horn): ccntalns motDr n~rons. • Lnen!l Clllumn (l;tter~l horn): contains symp;rthetic: or p~r~sym·

pathetic (visceromotor) neurons. • Postl!rtor column (postl!lfor horn): contains sensory neurons. The gray mattet' p.artitions the white mattet' analogously inm antzrior, l;tte~l ~nd PQm!rior funiculi. When the spinal cord is viewed in crosssection, tile gray-mat18' columns are traditionally nefaTed to as •homs.•

~rnargln.al

fasclc:&lus

{onlylntharadccard} lntl!rf.lsc'lcularl'.lsc!Wus ~ (only'hal'lllcalaard)

IJlngltudlnal

fa:~dculusof

_ . - - - - PhlfWe.Gomb;u.ft

tr1:1ngl~ (onlyln$;~Ct;~lc:ord)

/

pC~Sterlormumn

lol!l!ral----;;-., fasdcuh.s proprius

Suk:ornargln.al _ ___:;....;.._ _..::.;;;;....__

fasdcull5

B Prtndpal lrltJtnslcfiuddes of the spiMI Cllfd (shaded yellow) Three-dimensional representation, oblique anterior view from upper ltft. Because most of the muscles hiSVe <1 plurisegmental mode oflnnuvitlon,axonsmustbeibletoascendinddesc:endformul!lplesegments Wlttlln !he spinal ccrd In order to ccordlna!l! spinal reflexes (seep. 272).

268

The neurons of lhese .uons orfglnm from tntl!lni!Urons (see p. 271 E) in ttle gr;~y matter, which form ttle intriruic reflex pal:tlways of the spinal cord (seep. 273 C). These axons ire collected Into lnrrtmk (asdcks known also as (asdcull propdl. Arr.;mged chiefly <~round ttle gr;ay matter, these bundles make up ttle "Intrinsic drcults• ofttle spinal cord.

9. Spinal Ctml

Neuroancrtvmy -

'" i l.

Medula ~

~.,. I

Cervical onlorgemont

Poltl!flor

-:-1;: ,

oblongm

{

••

mocfanltJCUI

- - - -4-- sprnall'ltlalar Jam-.

1"

Utonlhom

Nft~---~~-~~---M

medlin ftuure b Cllvlc.lll aonll

c 'Thandc mnl

Slbmntli ~~~~~-­ Splnil~...

famlitlon Doi!CII.tw.ll nudeus

c:audoequlna

PoiWoYtftl

("hane's Ull')

tiKI: ~.....--

Apetofpasl:!tiorham !ollbmnlll

gelollnosa -..::.,:.;~,:...:.:;---.,.:+-+-

Centrllallll

Anterior --:::....:--~1\..WaJus

c PIIIIIIDn of the 1pln1l canl" the dunol~a~: a Anterior view with the vertebral bodies p;rrtlilly removed to display the anterior aspect of the splml core!. The tnnswrse sections (H) depict fibertr.ldl (left side, ~lin stain) and neuron ~II bodies (right side, Nlnl stain) at different levels of the spln;rl cord. The areas of the

c:erviul and lumbrosatral 01nlargement1 h;rve been demarcated (1). In these are.u, which pi'OY!de lnneMtlon to the limbs, the griY mattes" Is slgnlftca ntly exp;r nded.

269

9.3

Spinal Cord: Internal Divisions of the Gray Matter

Org~nlzidlollill plindpiH ofthe
A

Vtntnll

root

Neurons«

b

• B SomatotDplc:orglllllfzatSon of nude.r CDiumnt aftfle antertor hom (Jfu!r Bos.sy} <1 Common p<~ttem of organization ln tfle spinal cord. More medial nu· dear columns of the anterior hom Innervate musdes do~ to tfle midline. while more lateral nLJCiear columns tend to Innervate mus-

des outside the trunk. b Enlargement of cervical cord. The same patb!m of medial-to-lateral organ!Dtlon exJru (see a) With medial nuclei Innervating aXIal mus-

270

-nsoriTAIKiu

Medial nuclear~p

cle~ and lateral nuclellnnervalfng muscles at tfle extremities. HoweYer, thene Is also an anterfor-tD-postl!rtor segregation of motDr columns. Neurons $C!Ning extensor muscles (shades of blue} are found In tfle most ~nterlor parts of the antertor horn. while those sei'Ying flexor muscles {shades of pink) ire found In tfle more pos!2rtor regions.~ nudel are further dllllded Into: • Medial nuclei: innervate nuchal, back, intercostal. and abdominal muscles • Anterolateral nudeus: Innervates shoulder girdle and uppef arm muscll!l • Posterol;ateral nucleus: innervata fore.o~rm muscll!l • Retroposterolate!'al nude~JS: Innervates small muscles of tfle fin-

gers

Nuc:lew; of

Antl!ramedlal

Nucleus of

acazarynenoe

nudeur.

phrenic ni!Nt'

c Cell groups Tn die gray ll'lllttl!rofdle spfnll --.1
I

Ill~

Ill~

;~

---x

VIII/ b

Mablr ....,n• (neurons whldl send aons In thewntral ro«tothesplnal

nftWand pertpheJY): • Somolkmotwnuons (lndudlng alpha and oamma motl)r nwrons) • 1/tlarolm(l(or neuR~m: .-.ngl!onlc neurons which Innervate gan-

glion cells. I¢ thon~columbar lewis these are JlN911nglionic sympathetic neurons; at mid-sacral lewis, these are pr.gangllonlc parasym· pathetic maiDr neurons.

-n• (neurons whldl SEnd aons to otherCNS locations):

• S«ondooy1ltMOIY-(tract Cl!lls): neurons which send their illCOIIS In asandlng tracts (whltl! matter). These neurons neCIM synapses

:~

--x VIII

~

VIVII c

IX

D SJ11ilptfc II,.I"Jinthagrqrn.rttar • Cen1lcal cord, b tftor.rclc cord, c lumbar cord. Motor neurons are shown In red, sensory neurons In blue. The gr;ty matter c3n 3lso be divided into lil)'l!rs of iXGn termination, based on cytological crttafa. This w.~s first done by the Swedish neuro-

~rf1151c

I

II~

w~~~~

VII~

•

of the spin31 nerye, wflereaJ the mare slender posterior (dorsal) horn contilns Ute all bodies of secondary sensory neurons ;md recdves the dorsal (sensory) root. The sensory neurons ofUte p0$tlerlor horn recellle synapse from enterl'ng processes of spinal (dorsal root) ganglion cells, and in tum send tfteir i!JCOns to other, mostly mare tr.!nial,leveb. Note: some ganglion cell ODCOns entl!r ascending tracts without synapsIng locally.

II~

rv

IX

Cen1r.ll nuc:lew;

I

II~

YPA~

Antl!rdmral nudeur.

b

---X

~

VIII IX

IX

;matomlst Bror Rexed (1914-2002), who divided the grq miltta' Into laminae 1-X. This laminar an::httecture Is e.spedally well defined lr1 the posterior (dorsal) horn, where prtmary sensory alQl!U make synapses 111 specifiC lil)lers.

Commlssur~l cells: neurons whose illCOIIS cross In the spinal white commissure to the contralatl!ral side. - Assodaaon (lntanegmentaQ cells: neurons whose illCOIIS lnb!rco~ nectd~spinal segments. - Rensh-cells: a spedflc type of lnhlbiiDry lntemeuron that Is a· dt&!d by amn collat&!rals from alpha motor neurons. The ea:lted llensh-celllnhlblb the motl)r nwron that stimulated It, and also nelghbolfng motor neurons. creating a negat~feeclback loop that modulaii!S the lhtng rat&! of the group of nwrons. The Renshaw 0!11 also syn11pses on other loa Iinhibitory neurons. and neceiws input from descending path~

-

fnlm primary sensory neurons whose cell bodies are In spinal (dODal root) ganglia. • l..oaJIInlmlewons: neuroM dlsb1buted through the gray - rwhose -srtmaln In the local sf)lnal cord (see C. p.27l). These lndude:

- lnterc.alatlecl ails: neurons w'- - s A!lllaln at the same segmenlllllewl.

Some of these distinctions are not e~~Jct. T111ct Cl!lls, fQr Instance, h-

collaterals that synapse locally. Sll«
271

NeurDGnatomy - - 9. SpliHII Cord

9.4

Spinal Cord: Reflex Arcs and Intrinsic Circuits Dorsal root

Posterior hom

P>eudounipolar

Ventral root

Alpha

Anterior

lnb!r-

motor neuron

horn

neurons

A Integrative function of the gray matter of the spinal cord: reflexes

Affererrt nerves are shown in blue, effererrt nerves in red. Black indicates neurons of the spinal reflex circuit. The gray matter of the spinal cord supports muscular function at the unconscious (reflex) level, holding the body upright during stance and enabling us to walk and run without conscious controL To perform this coordinating function, the neurons of the gray matter must receive information from the muscles and their surroundings; this information enters the posterior horn ofthe spinal cord via the axons of neurons in the spinal ganglia (see p. 328). Two types of reflex exist: • Monosyn•ptlc reflex (left): intrinsic reflex in which information from the periphery (e.g., on muscle length and stretch) comes from the muscle itself. Receptors in the muscle transmit signals to

a

b

B Clnlc.lly Important monosynaptic refll!lU!s a Bleeps reflex. b triceps reflex. c patellar reflex (quadriceps reflex), d Achilles tendon reflex. The drawings show the muscles, the trigger points for elldtlng the reflexes, the nerves Involved In the reflexes (affererrt nerves In blue, efferent nerves In red), and the corresponding spinal cord segments. The principal monosynaptic reflexes are should be tested In every physIcal examination. Each reflex Is elicited by briskly tapping theappro-

272

alpha motor neurons via neurons whose cell bodies are in the spinal ganglia. These afferent neurons release excitatory transmitters which cause the alpha motor neurons to stimulate muscle contraction (see D). • Polysynaptic reflex (right): reflex mediated by receptors in the skin or other sites outside the muscle. These receptors act via interneurons (see C) to stimulate muscular contraction

prlate tendon with a reflex hammer to stretch the muscle. If the muscle contracts In response to this stretch, the reflex arc Is Intact. Although each test Involves just one muscle and one nerve supplying the muscle, the Innervation Involves several spinal cord segments(= multlsegmental muscles, see A. p. 270). The right and left sides should always be compared In clinical reflex testing, as this Is the only way to recognize a unllmrol Increase, decrease, or other abnormality.

PseJ clou nlpol;l t ~• body In spinal gan~fon

Allan callro!nl Alpha mGCilr neuron

D Efl\ectsofthe Renshaw cell onthulpha mlltDrneui'QII

c

CQmpanents of tile tntlinskdrallts oftile spl'nll coni J\fl'erent neurons are shown In blue. efferent neurons 111 red. The !leU· rons ofthe spinal refleK circuits are shown 111 black. Poly3ynaptlc reflexes ofte11 must be coordinated at the spinal cord lew! by multiple segments.lnterneurons. some ofwhose.w~nsshowa T-shaped branching pattl!rn, COfM!Ythe afferent signals to higher and ICIWer segments <~long crossed and unc~sed pathways (types of lnterneurons are deKr1bed ifl E. p. 271 ). These chains of intemeurons. 'Whldl are enlfrely contailled within the spinal cord, make up the intrirlsicciratits of the cord. The axons of the neurons In tile Intrinsic clrtUits pass to adjacent segments In l11trfnslc fisdcles (faKicull propr11) located as the edge of the gray mat· ller (see B. p. 268). These fasdcles are the conduclfofl appar.rtus of the intrinsiccircuits.

The <1fl'erent flbers 111 a monosynaptic A!fle11. orlglniltt' 111 n~rons of the spinal ganglia. Theyte1111lnate on lht' alpha motor n~rons. where !hey release the excitatory transmitter .ilce~ollne. 111 response to this tr.ilnsmitb!r rele-ase, the alpha motor nl!l.tron transmits excitatory impulses to the neuromuscular synapse (the trar~smltter at the synapse Is also acetylcholine). The excitatory alpha motor neuro11 has iX011 collaterals that enable It to exert a stimulatory effect 011 an Inhibitory 111tem~ron ~lied a Renshaw cell. In response to this stimulation, the Renshaw cell releasH tile lnhlbitwytransmltter glycine. This St'!Hnhlbltlngmechanlsmservestoprevent<MroCCltatlonoflhealphamotorn~

rons (recuiTellt Inhibition). The clink:OIIImportance of the Renshaw cells is dramatically illustrated in patients with tztlnus. The tetanus !min Inhibits the rele-i~Se of glycine from tile Resuhaw eel b. l11hlbltion of the alpha motor neurons falls to occur. and so the patient experiences sustained {tetanic) musde contracaons.

~bUII)Ij)hal

tr.let

~bnls~~~~

~

OIIYOspillill tm:t

~era! (1)111<0-

lplllill tr.ICt

E IEifects of long tr.lcb 011 the<~lpha motor neuron

The alpha motor nl!l.tron not only reaWe$ ef· fenent ftben from the splr~al cord Itself. but Is alsostronglymodulatedbyefferentflbenfrom long tr~ru that ortgrnate iflthe brain. Most of theK' elli!rent fiber.s h;we an inhibin:lry el!1!ct on tile alpha motor net~ron.lfthese effects are ibollshed due to a complete cord lesion, for eKample. the disproporlfon.rtl!!ly strong inti~; ence of the spinal intrinsic circuits will lead to spastlc paralysis (seep. 343).

Annubsplral Abet (li)

Alph;l momr neurcn

273

9.5

Ascending Tracts of the Spinal Cord: Spinothalamic Tracts

/~;:z:;;.__,..:----

Mll!rlar-....;;.-...,..----'

Cdlbodyof SI!CIOI'Idneuron

::::---==4===::=

Sacral

wmb~r

!plnotflalamlc

1ract

1horadc

1--- ---:- - Amneuvn

CeUbodyof CAI!ilbodyof seax1dn«~ran

A Course of tile illtlerfor ;md lat.erill splnotflillillmlctrilds rn ill tranrwne sec:Uon of tile spinal GIRl See p. 284 for OIII!Niew of aKI!nding tracts. The amos of the anterior

splnothalamlctr.Kt run lrlthe anterlorfunlculus ohtte spinal cord. wfllle thos;e of the lata"al splnothalamk tract run In both the anterior ;md lat· er.al funiculi. (These two tJacts are sometimes referred to collectively .u the on~om"ol funiculor lroct.) The anterior spinothal;amic tract is the p;lthway for aude touch and pressure sensation, while the lateral splnothalamlctractcorweys pain, temper.ttllre, tickle, ftx:h, and sexual sensation. The ceU bodll!l of the pnmary afferent neurons for both tracts are located in !he spinal ganglia. Both tracts contilin second ~I'WIS

274

\

plfm ary .alferent ne uran

In spinal gan91on

and cross In the anterior commissure. The somatotopk organlz.ttlon of the lateral splnoth.al.amlc tr.act Is shown on the left side of the diagram. Starting dcn.1lly and moving clockwise. we suaHSM!!y ena~unter the sacral,lumbilr. thorilck. and cervical flbers. In older terminology a distinction Is sometimes driW!I betwHn fPktltic and pratopothlc sensittton. Accordlng to this temllnology, the .antel'for and lateral splnothal;amic tracu are d
Neuroanatomy

- - 9. Spinal Cord

@Sensory cortex

@An~~or

spinothalamic tract

S'f:---'--------7--

An~rior

commissure

@First neuron Lateral spinothalamic tract

B Antl!rtor spinothalamic tract and Its central connections 1 Impulses from tactile corpuscles and from receptors about the hair

2

3

4

5

6

follicles are carried to the anterior spinothalamic tract by moderately large-caliber myelinated axons (dendritic axons). The cell bodies of these axons are located in the spinal ganglia (first neuron, primary afferent neuron). The axons pass through the dorsal roots and enter the gray matter, where they branch in aT-shaped pattem. These branches descend for 1-2 segments and ascend for 2-15 segments. The synapses of these axons terminate on neurons in the posterior column (second neuron). The axons of the second neuron form the anterior spinothalamic tract. They cross at the anterior commissure and ascend in the oppo· site anterior funiculus. In the mesencephalon, the tract runs in the medial lemniscus as the spinal lemniscus (the lemnisci are described in D) and terminates in the posterolateral ventral nucleus of the thalamus (third neuron, see A,p.218). The axons of the third neurons terminate In the primary somatosensory cortex, which Is located In the postcentral gyrus.

C Lateral spinothalamic tract and Its amtral conni!CI:Ions 1 Free nerve endings in the skin function as receptors for pain and tem-

perature sensation. 2 The cell bodies of these free nerve endings are located in the spinal

ganglia (first neuron). 3 The central processes ofthese neurons pass through the dorsal roots

into the spinal cord, where they terminate on projection neurons in the substantia gelatinosa (second neuron). 4 The axons of the second neurons cross in the anterior commissure in the corresponding spinal cord segment and ascend in the anterolateral funiculus on the opposite side. They terminate in the thalamus (third neuron). 5 The axons of the third neurons terminate in the primary somatosensory cortex, which is located in the postcentral gyrus.

D synopsis oftfle lemnlscal tracts (lemnisci) Cerain sensory pathways cross in the form of a lemnlscal tract (lemnlslrus ="ribbon"). The characteristics of the four lemnisci are reviewed below.

CaniiKtlon

FunctloMihporblnce

Lateral lemniscus

Trapezoid body/s~riorolivl! with i~rior colliculus

Auditory pathway

Medial lemniscus

Dorsal column nuclei (gracilis and cune.atus) with thalamus

Touch, conscious proprioception (seep. 284) of the trunk and limbs

Spinal lemniscus• (borders the medial lemniscus)

Poswlor horns (lateral and arnrlor spinothalamic tract) with thalamus

Pain pathway for the trunk and limbs

Trigeminal lemniscus (borders the medial lemniscus)

5ensory trigeminal nudel with thalamus

Sensory pathwayforthe head

• The spinal lemniscus Is the portion of the anterior spinothalamic tract IOCilted In the mesencephalon. The course of the anterior spinothalamic tract In the brain stem is not fully understood, and therefore cannot be dearly depicted in these diagrams.

275

9.6

Ascending Tracts of the Spinal Cord: Fasciculus gracilis and Fasciculus cuneatus

A Ala!ftdlng aons Tnthe fllsd'Nus grad Is and filsc'lalkll aJ~s

See p.284 for overview of ascending trncts. The fasclaJIIIS gracilis ("slender f.l5dcuha") and fasclculus aJneatus ("Wedg~sbaped fas. ticulm•) ~re tile ~ large ~scending mm lr1 the posterior fur~lculus. Both tmn corwey fibers for poslt:lor1 sense (consdoiiS propr~ ceptlon, see p. 284) and tlne cutafii!OUS senS
Cell bodyd ftrrt .ilfterentneilron

- - Sphllgangllon

276

Medial lemniscus

~lmllrglnal

fadcuw (cffltdmg)

__;~:---®

T

l ) 11londc coni

Phil~ ~

Gombll.lt

triangle

~

)

B DtsatndlngBDns Besldn the ascending axonJ oont
c

T'rlds aftfle posteliorfun'lallusand tflelr aentnl CDnnedtDns 1 MuKie and wndon n!aptors. and Vater·Paclnl corpusdes ane receptors for conscious proprioception. Receptors about the hair follldes .ilnd addltfon.al receptors medlm Ute tlne touch sensation of the

skill.

2 The all bodln of the neurons that relaytfiiJ Information are located In Ute spinal g<~nglla (first neuron}. 3 The uons of these neurons .iiKend uncrossed lntfte posterforfunlalll to the nucleus cuneatU$ and nucleus gr;!o1is (second neuron) in the lower medulla oblong<~ta. 4 The allOnS from Ute second neurons cross lr1 the medial lemniscus (seeD, p. 275) to Ute thalamus (third neuron). 5 The axons of the lflird neuron terminatl! in the primary somatosensory cortex, lot<~Wd In the postmttral gyrus.

2T1

9.7

Ascending Tracts of the Spinal Cord: Spinocerebellar Tracts

T

rI

I Y ~Ot

•

splnoanbdarlllltt

.....;........,..,....;- - Anteriat '!llnaonbelarlllltt

Cel body of mx~nd

neuron In pasb!rlar ham ohplnal cord

A Antlerfor ;md postll!rforsptMCerebellilrtnlcb Seep. 284 for ovel'\llew of ascendll'lg tracts. 8oth tile anterior ill'ld pos· tzrior spinoa!rebeUar tracts are loc:ated in the lateral funia.lus of tile spinal cord. Their afferent fibers. which convey afferent Impulses from muscles. tendons. and Joints to tile cerebellum. are lnYOived 11'1 tile un· conSCious coordlnatlol'l of motor actiYIUes (unconscious proprtoceptlol'l, automatic proceues below the conKiouslevel, wch as jogging ;and rid· lng a bkycle. seep. 284). The projection (second) nNrol'l5 of both spl· nocerebeUartrilcts recelwoe tllelr proprfocepttlle signals from prfmary af. ftrent fibers ortglnatlng at the first neurons of the spinal ganglia. 11'1 tile antlerlor splnooefebellllr tnd,the sea~nd l'leU~s are located in the dol'lil gray hom. Their projectlol'l flben ascend both Ipsilaterally and

278

controlah!ral/y to the cerebellum via the wpafor cerebellar ~uncle. The semnd neurons of the postertor tpl'nocerebellllr tr11c:t are located

in the postJ!tior thoracic nucleus of the posterior horn; this nuclear column spilns segments C8-L2. The project!ol'l fibers from these seco!'ld neurons ascend lpslltm!rol/y to the cerebellum via the l!'lfertor cerebellar ~uncle. Botll tile antertor and posterior spinocerebellar tracts h- the $ilme somatotopic org;aniution from front to bade: thor;acic {T),Iumbar (L). and $i1Crill (S) fibers. Aben of similar fui'ICtiOI'I from the arvlal/ region pass through the filsclculus ameatus to tile il«~sory cuneate nudeus and continue as cuneocenebellartlbers to the cerebellum. However, these do not pa$$ through the posterior spinocerebellar lr.!lct. which contains no fibers from tile cervical cord.

Neuroanatomy - - 9. Spinal Cord

Inferior Cl!l'ebt!llar peduncle

--~---Gil),

.....,-----lf-+-- Anll!rlor spinocerebellar

tract

@Cell body of semnd neuron

B Anterior spinocerebellar tract and ltl central connections 1 Proprioceptive signals from muscle spindles and tendon receptors are

carTied byfast-conductlng myelinated axons (lA fibers) to pseudounlpolar first neurons In the spinal ganglia. 2 The signals then proceed to the second neurons (projection neurons of the anterior spinocerebellar tract) In the dorsal gray horn. 3 The axons of the second neurons ascend both Ipsilaterally and controlateroi!Yto the cerebellum and then pass through the floor of the rhomboid fossa to the midbrain. 4 Once In the midbrain, the axons change direction and pass through the superior cerebellar peduncle and superior medullary velum to the vermis of the cerebellum.

0

Cell body of

serond neuron

C Posterior spinocerebellar tract and Its central connections 1 Muscle spindles and tendon receptors convey proprioceptive Information via fast lA Hbers that arise from pseudounlpolarfirst neurons In the spinal ganglia. 2 The lA fibers proceedtothesecond neurons ofthecentral gray matter. The second neurons are contained In the ltloraclc nucleus, which spans spinal cord segments C8 to L.2. 3 The axons of the second neurons (projection neurons of the spinocerebellar tract) ascend Ipsilaterally to the cerebellum, entering through the Inferior cerebellar peduncle.

279

9.8

Descending Tracts of the Spinal Cord: Pyramidal (Corticospinal) Tracts

~an------~

ofP'/lllmkb

Alpha - - - -"7' motl)rnef.Jil)n

- - Spiral cord

A Coune of die lllterfor l!rtd l1b:l1ll cortlcosplMIIF
280

nilte at the aanlal nerve nuclei while others, die cortlcosplnolflbm, terminate on the motoranterlorhomcellsoflhesplnal cord (see8forfurther details). Athird grcup, Ute oortlaJrel:tallar fibers, .ilre distributed to

nuclei of the retirular formation.

Neuroanatomy - - 9. Spinal Cord

Pyramidal --;f-----.~--."""- ""'l:rll-f-.:!--.,.-----'c.t-----'\-- lntelllill tract capsule

C Sliver-Impregnation (Colgl) method sbllnlng of pyramidal cell (4) L.ater.~l corticmpinol (pyramidal) tract

This method produces a silhouette of the stained neurons. The axons of the pyramidal cells form the pyramidal tract. Approximately 40% are located in tile motor cortex (Brad· mann area 4, see p. 202).

~----~-t--lntemeuron

'it-- ---;:-+-- @Alpha motor neuron

®Anterior cortico•pinal (pyramidal) tract

Anterior medlilnflssure

B Course of the pyramidal tract 1 The pyramidal tract originates In the motor cortex at the pyramidal cells (large afferent neurons with pyramid-shaped cell bodies, see C). The pyramidal tract has three components: • CDrticonuch!orflbers for the cranial nerve nuclei • CDrticosplno/flber5forthe spinal cord • CDrticoretlculor fibers to the reticular formation 2 All three components pass through the Internal capsule from the telencephalon, continuing Into the bralnstem and spinal cord. 3 In the bralnstem, the cortlconuclear fibers are distributed to the motor nuclei of the cranial nerves. 4 The corticospinal fibers descend to the decussation of the pyramids In tile lower medulla oblongata, where approximately 80% of tllem cross to the opposite side. The fibers continue Into tile spinal cord, where they form the lateral corticospinal tract. which has a somatotopic organization: the fibers for the sacral cord are tile most lateral, while the fibers for the cervical cord are the most medial. 5 The remaining 20% of corticospinal fibers continue to descend wltll-

out crossing, forming the antl!rlor rorticosplnal tract, which borders the anterior median fissure In a transverse section of the spinal cord. The anterior corticospinal tract Is particularly well developed In the cervical cord, but Is not present In the lower thoracic, lumbar, or sacral cords. 6 Most fibers of the antl!rlor rortlcosplnal tract cross at the segmental level to terminate on the same motor neurons as the latl!rol corticospinal tract. The axons of the pyramid cells tenmlnate via Intercalated cells on alpha and gamma motor neurons, Renshaw cells, and Inhibitory lnterneurons (not shown, see p. 273, C). Lesions of the pyramidal tract are discussed on p. 343. Other motor tracts are closely applied to the pyramidal tract In tile region of the Internal capsule and will be described In the next unit. While the pyramidal tract controls conscious movement (voluntary motor activity), supplementary motor trocts are essential for Involuntary muscle processes (e.g., standing, walldng, running; seep. 342).

281

9.9

Descending Tracts of the Spinal Cord: Extrapyramidal and Autonomic Tracts

Anllrtor c«ttaalplnal tract - - - : - - - - Ubnla>rtkD-

•plnaltract

----+-:---- Rub""f'lnalandtract ~cuiDSplnal

A T'rKtl of the Gt1'8J¥11mldll mlllllr system In tfle 1p111111 CDrcl See p. 285 for owrvlew f1f descending tracts. Unll~ the pyramidal tnoct, which controls conscious. voluntary motDr activities (e.g .. rals· lng a cup to the mouth), tile e.wttllpyramlclill motDr system (cerebel· lum, bas;~ I gangli01, and motDr nucl~i of the brain~m) is ne~Hry for ootomolk and lmmrd motDr pro~ses (e.g.• walkfng. running, cydlng). The division Into a pyramidal ilnd extrapyramidal system has pnoYen useful In cllnlal practice. A recent .alternatlw daulflcatfon dl· vides th~r descending tncts into a liiteriil il nd m~iil system. Und~r tills duslflatfon. the lama/ ~lrm lndud~ • Lltl!ral cortlcosplnill tract(- pyramldil trilct, seep. 280) • Rubrospinal tnct (extrapyramidal)

The lateral system projects predominantly to the distal muscles, particularly those afthe upper lim b. and th1.11 critically influences flne, discriminating motDr functions of the hand and urn. The ~lui symm projects millnly to the neurons of the trunk .;md lower limb musdes and Is thus concerned with the motor aspects of trunk posJUon and stance. The media/.I)'S!MI consists of three exlr.lpyramidal tracts: • Anterior retlculosplnal trut • Laterill vestfbulosplnil trilct • Tectospl naltnct The centrilf connections of this system are lflustril~ In I . Because the pyril mIdill ilnd u.tnpyramldal tracts are dosely lnt«aannected and run close to one other, lesions generally affect bath tract systems simultaneously (see p.343). Isolated lesions of either the pyramidal or e~~trapyramldal path wily ill: the spina I cord 1~1 are virtually unknown.

282

tid>'.,..,.......... c•·

I Clftlnl DffQIIUnd CIIUne afthe Delilnlund Gehlen) The nude! of oltgln of the extro~pyDmld~

tr
Submnlll nlgr.1

Tec!Dopml !net

Alotla.obspln.l tract

Flbon for gonltll fulcdon, u~l'llllon.and deii!Citlon

C Autllnamk piltlnnys ufthuplnll c:ord Autxlnomlc jNthways h~ve a somewhat diffuse amongement In the .spinal ami and rarely fu!m closed trtct systems. There are two eR>eptlons: • The desc:endlng arrtral sympithetlc tract for vuoconstrtctlon ilnd Flbonfar-vasoaJnstrtdlon•nd

-·ec-n

sweat secretion borders the pyramidal tract anb!riorly and shows the Sil me solllitDtoplc organlz~lon iiS the pyr1mldal tr~et. • The jNrependymal tract runs on both sldti of the central canal ilnd contilins both llllcending1nd descending fiben. PaS$ing from the spi~ cord to the hypoth•l•mus, thIs trilct b concerned with uriR<~Ifon,

defecation, and genital functions.

283

NeurDGnatomy - - 9. SpliHII Cord

9.10

Tracts of the Spinal Cord, Overview

Tracts ofth~ pos~rlorfunlculus

Fasciculus gracilis

Fasciculus cuneatus

Posterior spinocerebellar }

tr.1ct

Spino·

Anterior

a!n!bl!llar tracts

spinocerebellar tl'olct

Anterior spin<>-

thalamlc tract

A Ascending tracts In the spln•l mrd Transverse section through the spinal cord. Ascending tracts are afferent(- sensory) pathways that carry information from the trunk and limbs to the brain. The most important ascending tracts and their functions are listed below. Spinothalamic tracts - Anterior spinothalamic tract (coarse touch sensation) - Lateral spinothalamic tract (pain and temperature sensation) Tracts of the posteltor funiculus - Fasciculus gracilis (fine touch sensation, conscious proprioception of the IOWI!r limb) - Fasciculus cuneatus (fine touch sensation, conscious proprioception of the upper limb). Spinocerebellar tracts - Anterior spinocerebellar tract (unconscious proprioception to the cerebellum) - Posterior spinocerebellar tract (unconscious proprioception to the cerebellum)

284

Spinothalamic tr.lcts

Proprioception involves the perception of limb position in space ("posi-

tion sense"). It lets us know, for example, that our arm is in front of or behind our chest even when our eyes are closed. The information involved in proprioception is complex. Thus, our position sense tells us where our joints are in relation to one another while our motion sense tells us the speed and direction of joint movements. We also have a •force sense• by which we can perceive the muscular force that Is associated with joint movements. Moreover, proprioception takes place on both a conscious (I know that my hand Is making a fist In my pants pocket without seeIng It) and an unconscious level, enabling us to ride a blcyde and climb stairs wlthoutthlnldng about it. The table on p. 327 gives a comprehensive review of all the ascending tracts.

Neuroanatomy - - 9. Spinal Cord

-;;;;=---';---- Lall!ral mrticosplnal trod:

Rubro5pinal tract

Antaiormrticospinal tract

B Descending tr01cb In the spinal cord

Transverse section through the spinal cord. The descending tracts of the spinal cord are concerned with motor function. They convey information from higher motor centers to the motor neurons in the spinal cord. According to a relatively recent classification (not yet fully accepted in clinical medicine), the descending tracts of the spinal cord can be di· vided into two motor systems: • utenl motur system (concerned with fine, precise motor skills in the hands): - Pyramidal tract (anterior and lateral corticospinal tract) - Rubrospinal tract • Medial motor system (Innervates medially situated motor neurons controlling trunk movement and stance): - Reticulospinal tract - Tectospinal tract -Vestibulospinal tract

Tectospinal trod:

Vestibulospinal tract

Except for the pyramidal tract, which may be represented as a monosynaptic pathway in a simplified scheme, it is difficult to offer a simple and direct classification of the motor system because sequences of movements are programmed and coordinated in multiple feedback mecha· nisms called "motor loops• (seep. 341 ). There is no point, then, in listing the various tracts in a simplified table. While the tracts can be distin· guished rather clearly from one another at the level of the spinal cord, their fibers are so intermixed at the higher cortical levels that isolated motor disturbances (unlike sensory disturbances) essentially do not occur at the level of the spinal cord.

285

9.11

Blood Vessels of the Spinal Cord: Arteries

c:1;J

Vertl!bralartl!ry, lrrtr.acranlalartl!ry

'[,

AnUrlof lpln.alartl!ry

Rlltlt - ----......... ~~

IJ!ftVI!!Ubral artey

artey ilntl!r1ar

SlbdiMan artey

meduhrr

~ntal

~

MUIY

Gn!l1t anll!rlof Hgnent.ll

"

medLllaryartl!ry Pos1!riOt 1~1

art«)'

b

A Artl!ft'll blood tupp~tD the tp1n1l ClDfd (al'a!r Nieuwenhuys) hrtaforvlew. ;~ Overview of the arterial supply sysll!m. b Vessels supplying the Wftkal systl!m. c Wmrshed ~re.as In lfle vertical sys· b!m.

The arterial blood supply to the spinal cord Is dertvedfrom both vertical ;md horizontal com· ponents. The vmtca1 S)'Stl!m consists of tile un· paired onterior 'SP''nol ortmes and the paired posl:l!rlor spinal Cll'tl!rlfs. The spinal arteries typically .arise lntracr.anl.ally from lfle vertebral arteries, lflough the posterior spinal arteries rmy arise from lfle posterior inh!rior «rebc!llar artay. The descending spinal arteries are small where they originate at lfle vertebril ar· b!rles, and would significantly decrease In caJ. iber without reinfllrting contributions from tile antafor and posterior segm111t.1l med· ullary arterfts. These segmental medullary vessels arise from spinal br.anches of the Vl!r· tebral, ascending cervical, deep cervlc;rl, posterior Intercostal. lumbar. ;md lateril saaal arteries, depending upon the level of the spinal cord. The segmental medullary vessels v.ary in both their lewl of origin and number (an aver· age of 8 interior. ind 12 posterior arteries ire seen). Or~e of lhese arteries, the great antertor segmental medullary artery (of Adamkiewicz), Is usually significantly larger thin the others, and reinforces the blood supply to appi'Old·

286

c

miltelytwo-thlnds of!he cord, especially In the thoracolumbar region. In 65 !1: of individuals it irises from tile left side, typically at T12 or L1. illflough It may irfse anywflere between 17 tD L4. At .all other Yertebral and spinal cord levels, smalll'lldl~lw artedet arise from the spinal brandles ind supply the ventral and dorsal nerve roots, .as wen as the perlpher.al po!11ons of the antl!lfor ~nd posterior horns. The radicular arteries do not re;ac:h or contribub! to the spinal irterfes. Since the spinal irteries receive v.arl~ble relnforamentftom segmental meduf. lary arterie.s, certain te9ions of the spinal ccnd may re~ lfleir blood supply from multiple souras (see c). RestJfctlon of blood supply at such .ilte9lon may result In Ischemic Injury tD lfleccnd. TheT1-T4andtheL1 ccrdsegments a~ particularly vulner~ble.

Anb!r!or----l~.;,......-~~ 5PNI~rtay

"'---~ segmemal medl.llary

~~~~;;~~~~~~~= =~th

Sl!gmen!al medl.lllry

B Blood Sllpply to the tpiMI alflltegments In each spinal ami segment. the arr!Mor spinal artwy gives off sever;ll (5-9) suiCill <1l't:l!fi8 which coul'5e posteriorly In the anterior median flssune. ~plea fly, each sulcal .ilrtefy enten one half of the spinal cord, supplying tbe antt!rior hom, base of the postl!rior hom, and tbe antt!rior and lateral funiculi (approximately two-thirds of the total<~nea) In that half: the sulcal arteries tend to alternate direction (left or right) tD supply both halves of the spinal cord segment. The p.ilred postenor spinal ortzries provide the blood supply to the posterior oAe-third of the cond, lrxludlng the posterior hom and funiculus. All thnee splnal<~rterfes con· tribute numerous delicate anastoiTIO$Ing Vil~n.. on the pial sur-

f.ace of the spinal cord which in wm send branches intDtbe periphery of the cord. The suit<~ I arteries <1ne the only end-arterle.s witt!In the spinal cond, <1rld their ocduslon may produce dlnkal symptoms. Occlusion of the ante!1or spinal artery at segment;~! levels may damage the anterior horn arid ventral roots n!sulting in flaccid p.iralysis of the muscles supplied by these segments. Ifthe pyrimldal tract In the lateral funiculus Is lrtVOIYed, spastic p.iralysls will dewJop bdowthe leslon level. An occlusion of the posterior splnal.ilrtenes In one or mone segments wlll.ilfl'ect the posb!rior hom and funiculus le~~ding tD disllJrbances of proprioception, vlbr.U!on, arid pressune sensation.

C Blood ft'IIHfuuppJ,Ing the spln1l cord Thor<~clcvenebr
the vasocorona. These arterles hi1Ye a bette!'· developed connection IMth the anterior spinal artt!ry at some leYels arid with the posttrlor spinal artery at other lev$.

217

9.12

Blood Vessels of the Spinal Cord: Veins

A Vl!ftous dral'nllge of thupl'NII cord (
Su~or---­ 'fl!lliav.J

1/tdu..ls.

~l----

288

Gommon I lac Win

Spinal win

Ant.ericr ntdculllrw!n

8 Venousdl'iltnageoh spln;~lcordsegrnent Antenor VIew fllMn upper left. A spinal cord segment Is dr.alned by the ;r~rior and pomrior spin~! veins. TheR vessels are louted witilin the pia mater ;md are lnterconr~eCted by ar1 anastomotic venous ring. Both veins channel blood through the radicular veins to the ln!l!malVI!ftl!bral venous plexus (see C). Ur1lllre !he ndlcularvelfiS, thevelnsfnskkthe spl· nal cord~ no Vi Illes. An result, venountasis m;ycause <1 hi!l;rrdous rbe of pressure In the spinal cord. Atypical cause of Increased lntramed· ullary venous pressure Is an arterlovellous fistula, 'Which Is ar1abnormal communication betweefl.afl.artery .and win In !he spln.al cord. Because the pl'e$$Ure in the ~rteries is higher th~n in !he veins, .arteri~l blood tends to enter tile velfiS of tile spinal cord til rough the fistulous connection. Thefls!l.lla wlll remain asymptomatic as long as the Intramedullary veins maintain an adequate drain.age c.apacity. But if the flow across the flS!I.IIa outstrips their dralnilge c.1paclty, the functions of tile spln.al cord will be Impaired by tile Increased pressure. This Is manlfelted cllnlc.1lly by disturbances of galt, spastic paralysis. and sensory disturbances. Un· trealz!d, the decompensated fistula will eventually ca1.11e a romplete functional transection of the spinal cord. The treatmmt of choice Is SIJrglcal coJTectlofl of the fistula.

wins C Vel'fllflr.ll vei'IOUI pll!lUII Tr.ansverse section VIewed obliquely from upper left. The veins of the spinal cord arid iu coverings ;rre connected to the internal vertebral venous plexus via !he radicular and spinal vdns.l.oc3ted lfl the f.lttytlssue of the epidural space. this plexus occupies the Inner drcumference of the vertebl'ill canal. The lntl!ll\al plexus Is con fleeted to the external vtl'tebr;~l venous plexus by tile inWvertebral arid bosivertebral veifiS. An.astomoses exist between tile tr1butary regions of the anterior and posterfor spinal veins. Oblique anastomoses are located lr1 the Interior of the spinal cord .and nn.ay exttnd owr several segments (not shclwn). These connections ~re particularly import;rnt in maintaining ;r constant intramedullaryvenous pressure.

~~~;--~~~~~~~!----.splexuiln epidural sp.oe

Posb!rfor ---H--1-~It long1111d1111011 ligament

the-·

D Eplcklral WIM Tn (after Nleuwenhuys)

~ ---==-~l4llilt-l

win

:.n-~:-.!-- utml

arid lumbarwrtebnl GIMit

PostErior view (vertebral can.al windowed). The Internal wins of!he spl· nal cord are Vilveless up to the point at which they emerge from the spiool dura mater. The internal vertebral venous plexus is connected by olhervalveless veins (!lOt showr1 here) to the venous plexus ofthe pros· tate. It Is reliltlvely easy for prostatic carcinoma cells to pass along the velnsofthe prostatic venous plexus tothesaCI'illvenous plexus arid de· stray the sum:~unding tissue. For this reason, prostatic carcinoma fh!. quently metastasizes to this region and destroys the surroundlr~g bone. resultfr~g In severe pain.

l!j)ldur.alw!n lntemill I lac vein

£xtemal I lac vein Antl!rlar

rnumal wrtl!ilral

wnousplexus

289

9.13

Spinal Cord, Topography

A SpiMI oord and sptn•l nerve In thevwtebllll CiiMI•theiiMII oftheC4vertebra

.~-1:-l!rr---- Postl!rior lntlmill

ll'anM!I'Se secUon VIewed from ~bove. The spinal tord cuxupies the center of the vertebral foramen and Is anchored within the suba· ruhriOid spiCI! !» the spinal dura rn;rter by the denticulate ligament. The root sl-. an outpouchlng of the dura mater In the lntraYer· lll!bral for.amen, conulns the spinal ganglion and the dorsal and ventr;l roots of tile spinal nerve. The spinal dura mater Is bocJnded externally by the epldur.ill space, which conurns veno~JS plexuses. fat and connect!Ye tissue. The epldurill spice exlll!nds upwards as far as the foramen magnum, where the dura becomes fused to the cranial perlomum (see p.191).

8

Cauduq~lnailtthelevel of

thel2 Vl!ltl!bl'll Transvene $«lion viewed from below. The spinal cord usually ends at the level ofthe first lumbar vertebra (L1). Thespacebelowthelowerend of the spinal cord is occupied by tile caudil equlna and filum tamlnale lr1 the dural S.iiC (lumbar dstem, see p. 191), which ends at the level of the S2 vertebr
290

wrUllral wnous plexus

~--~~--~----~Y lnb!mll wrt!hl'lll

wnous plexus

~~--DuraiHt

(lumb.lrclstm!)

Sp(nal

dur.unmr

C C..ud;a eqlln;aln the vertll!br.JI c.Jn<~l Posterior llfew. The laminae and !he doJYI surface of the s.aaum have been partially tl!mcwed. The spinal cord in tile adult tl!rminates at ap· proximately level oftheflrst lumbarvatcbr.~ (l1). The dorS<~I and ven· trill spinal nerve roots extending from !he lower end of the spinal cord (conus medullarls) are known collecUvely as !he cauda equtna. Durtng lumbilr puncture at this leYel, a needle Introduced Into the subarach· nold spac:e (lumbilr clstem) normally slips past the spinal nerw IW1:$ without Injuring !hem.

•

D 1be spinal cord, dur..l sac. and Vlftebral column at different ages Anterior view. As. an individ.aal grows, tile longitudinal growth of the spi0011 oord lnae<~slngly lags behind that of the venebral column. At birth the distil end« the splnil cord, Ute conus medullarls. Is at the level of the L3 vel1ll!bral body (Vmere lumbilr puncture Is con1ralndlcated}. The spinal cord of a tall adult ends at the T 12IL 1 levei,IM'IIIe that of a short adult extends to the L2IL31evel. The dural S
E Lumbar pund:U~ epidural aneftfle.t~:a, and lumbar antstflesll In prepar.~tionfor a lumbupuncture. the patient bendsfarforw.rrdto separ.~tetfte spinous processes of!he lumbar spine. The spinal needle Is usually Introduced betweentftesplnousprocessesofthe L3.afld L4vtftebrae. It is ad...anced through the skin and into the duti!l s;ac (lumb.u cistern, see D) to obtain <1 cerebrospinal fluid Simple. This procedure has numerous applications. lndudlng the diagnosis of meningitis. For eplcln'lllnesthesll, a catheter Is placed In Ute epidural space Mthout penetr.ating the dural S<~c (1 ). I.IJmbar antstheill is induced by injectIng a local anesthetic solution Into the dural sac (2). Another option Is to pass the needle Into !he eplduril space through the Silerill hiatus (3). b

3

291

Neuroai'H1tomy - - 10. S«ttonGIAnatomyaft:ltdraJn

10.1

Coronal Sections: I and II (Frontal)

~~~~------~~~~~~~--~~

an!llr.ll fts.surrt

lntenalap:sul~.

allt8iorllmb l.iJb!t'alllltus

Optk: Oem'(CN II) Oa.fommrn~(CNIII)

Tnxhlmrnl!l"<<e(CN IV)

T11gtmln.11 nl!m'(CNV},

------'"''ii ----~

.sensoryroct

Gln~nl ntm~rb on Mdfonill br.J" inltomy

The series of sections {coronal, trilnsverse, ;md s;~gtttal) In this chapter Is Intended to help the reader gain an appreciation of the three-dlrnensi~n~l ~n;atomyof the br;!in, This is nete$s.1ry fwthe correct interl)reu· tlon of modem sectlonal Imaging modaii!Ses (CT and MRI for the lnW"eStlgatlon of suspected rtroke, bralfl tumors. menlngiUs, ;md trauma). In Dlll!ting this synoptic perspective, we assume that the reader has read the previous chaptm and has gained at least a general appredatlon of the functional and de.scrlptlve anatomy of the brain. The legends and espedally the small acccmp.mylng schematic diagrams .ilre Intended tD fac1itate a three-dimensional undersunding of the two-dimensior~al sect!om (the plane of the sectlon lfl ~flgure Is lndlcited by a red line In the small. Inset Image). The planes of sectlor1 have been selected tD display the structures of gf'l!lltt!St d1nlaJI 1mportx:ri'ICI! more dearly thar1 can be done 1r1 actual tissue secdons, which are not always optimally fixed and preserved. Because the sections were modeled on specimens uken from different lndMduals, some structures will not be found at the same locatlor11n every figure. The structures of the brain were assigned to specific onto· g>metlc regions In preYious chapten. and these relationships are sum· rn;arfzed In 8, p. 315. at the end of this chapter. Nate the relationship of the sectSonal planes tD the Forel axis In the anb!!tior part Df the braifl.ilnd tD the Meynert axis in the brainstem regiDn (see D.p. 185).

292

A Coron..l MC\kln I The body (trunk) of the COIJlUS col/osum, which Interconnects the two cerebral hemispheres, Is prominently displayed 1r1 this cnronal section. Superior to the COIPU$ callosum is the cingulok gyrus, which ~!so appears lfl subsequem: sections. Inferior tD the corpus call0.11.1m Is the caudatl! nudr!us, ~Mllch .appears particularly large because this sectlofl passes through the widest pottiDn of its head (see C). The nucleus appeiirs different In later sect!om because lttlpm acdplullytD a narww ull (seethe units that follow}. The sdtematlc later.!! view (C) shows how the caudate nucleus Is dosely .applied to the lo!:trol~ and follDWS its concavity (shown in green). The caudate nudeus and the puftlmm together form the corpus S!Ticrtltm.. whose "striatlor~• Is formed by the ;rntufor limb of the InterN! capsule. a streik of ~Mllte matter. The puumefl still appears quite small at this level because the section passes or~ly through Its anterior tip. It becomes larger as the planes of sect1or1 move further occipitally. The structures on!erlortD this plane consbt of the cortexandwhltem<~tterofthefront
5'!l7llm pelud~m Exl:emll apsule Optfctr.lct

OaLIItrUm

Amygdaloid body

Oculomotor neve (CN II) Troc:hiM' naw(CN IV)

nlgemlnall'll!l'lle(CNV),

sensocynlOt

- - - -"iliii

8 Coron;IIHC\Ion II This sectfon c011131ns essentially the s;~me structures as In A. The plane no longer passes through Ule heod of the can date nud~,1nst2ad pass· ing through iU slender oody. The inferior hom (U!mpor~l ham) Ill the late!'al ven!Jfcle appear'$ as a slttllke structure and also provides a useful landmark: ventral to the lnfel'for hom Is a portion of the porohlppOctlm· pol gyrus. Superior and medial to the infl!rior horn are the ornygdaltte

(amygdaloid bodies, visible here far the ffrst time: compare with D). They are bordered by the uncus, ¥>fllch Is Ule hook-shaped anterior l!nd of the parihfppocampal gyrus. The lntem:al apsule, which pierces the aiiJIUS striatum, appears a~nsiderably thichr in this plane than in A. The temporal lobe has merged at this level with the rest of Ule telencephalon, and the Insulor«Jrll!Kls cle.ilrlyWible..

Pllne ofsection In I

C Relationship between the au date nudl!lls ;md later;~l 'IN!fiVtc:le. 18tlmrlllvlew.

D Amygdala Right later.allllew.

:Z93

Neuroai'H1tomy - - 10. S«ttonGIAnatomyaft:ltdraJn

10.2 Coronal Sections: Ill and IV

5
Globus pallldus,latual stgment

Oobus pallldus. medial st~JI'nl!nt Optlcuact

Amygdilli Oculomotor n~(CN Ill)

....Uralwntrlde, hom

umpor.~l

Trlgemln.ll n~(CNV), - - - -...-:; mataroot

A Coronill section Ill The Inferior (temporal) hom of the laterill ventlfcle appears somewhat larger In the plane of this 5ed:lon.ln the ventricular system, we Cin now He the floor afthe thinl wntritle (He B) and the suJTOunding hypothal· am us. The thal.1mus cannot yet be Hen, as It lies slightly abcwe and be· hind the hypothalamus. The an!Mor «~mmrssure appears In this plane as does the g/«l.bus palfidus, which consists of a medial and a latl!r.al seg· ment. The large descending pathway. the conlcosplnal tract, p;mn through the lnfemc/1 capsule!. which has a somatotopic organlz:.ttlon. The genu of the lntemal Cipsule trinsmlts axons for the pharynx, larynx. and jaw. The cOCJrse of these amns is shown schematieilly in C (the fomlx appears ln D). lhalamus E.o:;:~~t.:..i---;-- ln!AmllaPI\IIe,

postmlrlmb

llll\llilr

-.1:--~~~\.J

~

Clob~sl)illld~s

~~~~--~~~~

Qudat!t nudeu;

Claustrum

I Ventriall;ir syst.em IJ!ft lmral VIew.

294

Putamen

C OKneafthepyramldaltractlnthelntemaiGipsule Left ant:trlarvlew.

Sepblm peULICidum

t.ml'al glabuspalrdus

Putlmen

Medal globuspalrdus

l'xternal upsult

t.ml'al sobs

OaustnJm

Optic tract

l'xtn!meapsule

Amygdllll

Forrix.boctt OcUomo!J)r nenoe(CN Ill) lh.llamus Trochlmrn~(CNIII) ~lwn!Jfde,

Trigeminal neM (0111/), stnSOI')' root

umporalhom

D Coron;ll HC\Ion IV The division of the globus p.;~lllduslnto medial and lilteral segments can now be seen clearly. This section displays the full Width of both the rnfe. rigc-hornofthel;ater;l"""tricle;andthe~(beliM!dtobeimpor­

unt In the regula!lor1 of sexual behavior). While the plane In A passed through the .ilnterfor comml55ure, this more occipital plane slices the mammillary btldies (see E). Pathological changes in lfle mammntary bodin can be found during autopsy ofchronk alcoholics. The mammll· lary bodies are flanked on each side by the foot o{thf hfppoalmpus. An Important p.art of the Umble systl!m, the mammillary bodies are con-

nected to lfle hippocampus by the {omlx (see F). Due to the anatomical curvature ofthefornlx,lts cofiJmn Is visible lr1 more fro nul sections (see A), while ItS cruro .ilppear as Widely sep.;~rated structures In more occlplul sections (see c. p. 299). The septltm ~lucidum stretches betwl!en the fomlx and corpus callosum. fomnlng the medial boundary of the later.ill ventricles (see A and D). The first stJuctlJre of the brainstem, lfle pons. can also be identified in this section.

Corpus callosum.

trunk

Lumen of thlrdwn!Jid~

Fomlx.

coklmn

E MldAgllial sedfon through the diencephalon ;md bl'illnstem

F Mlmmlll;uybodtes;mdfomlx

l..lteril view.

295

Neuroai'H1tomy - - 10. S«ttonGIAnatomyaft:ltdraJn

10.3 Coronal Sections: V and VI

Plltlmen

Em!mal apnfe

Glob~apalrdus, --+=:::t::_::~~-.;..---­ lat!er.alsegment

lmt111 wntride, ten-coon~l i'lom

Fmblfa of N'ppocampus HpPoc:amp~s

A CoronilhldlonV The appearance of the central nuclear region has changed marlcedly. The caudatl! nucleus Is cut tvllce by the plane of this section. Its body bord~ the central partofthelatC!r.!lventride.~nd a sm.allp~rtionofits ~il borders the Inferior hom ofthewntrfcle(seeCand E). 8eau5ethehe:ad and body of the caudate nucleus rlm the lateral aspect of the anterior (frontal) horn and the C!ntral part of the lateral ventride, the caudate nucleus has a curved shape slmllarw that of the ventricular system (see C}. Thus, the tall of the caudate nudeus Is ventral and liltefillln relation to Its head and body. Paflel E shows that a coronal 5eetlon through Ute tail of the Cludate nudeus cuts the oa:ipi~l portions of the pull:lmen. A section In a slightly more ocdpltal plane may not contain any part of the basal ganglia at
become much narrower due to the presence of the tholt:rmus. visible here illong wfth Ute thalamic nuclei. This Is the flrst plane that displays the ctroro1d p/f!llus, 1/lttkh can be seen within Ute laterill ventricles. The chor· oid plexus exte11ds f'rvm the interventricular for.! men (not visible h-) Into the lnfufor hom. Becau5e the for
heed

G-ludite nlldeus•

....

I llll!d nucleus 1nd substantSI nlg111 Midsagi~l section.

296

c Ventlfcullr system Superior view.

~~1------~~~---7----~~ affi)ral ftuure

Harlzonl
D Coron;ll HC\Ion VI The a udal !Niilmlc nuclei are well displayed In this section, border· lng the lateral ventncll!l &om bekliN and the third ventrkle from the ~H. The putamen lin Jt a mol1! oral level and i$ no longer visible in this plane (see the transvene section on p. 306). This section passel throughtheposteJtorlimbofthelnternalcapsule(seealsoC, p.294)and the anterior part of the postrricJrCDtnmissu~ (seeD, p. 299). The medirll

01nd krterol gmlwlote bodlfs. which are components of the auditory and visual pi!!hways, appear as two daricEr nuclei that flank the !Niilmus on the right and left sldl!l.iltthe same !eYe! as the commissure (see F). The crura of the fornix an be seen betwftn the thalamus and corpU$ ullosum. This Is the first section thJt pi!sses through part of the Cl!l'fbtllum. Here the mfddlec:ell!btllar pe®nde passes laterally toward the e«ebellar hemispheres.

Plant of

Thlrdwntrlde

secllonlnD Caudill' nude us SUpo:rfor (l)lloulus

J~d~~li;;;t,L- genlculat!e Medtll body

Inferior

callalus

E T0f101r.Jphlal re!atlonshtp between the Ciludate nuc:le4ls .1nd wntl'laJIIr system

Later.a! genlculat!e body

F 1be dlei'ICll!flhalon (wtth 9tnklllm bodies) met br.ltnstem Posterforllfew.

297

Neuroai'H1tomy - - 10. S«ttonGIAnatomyaft:ltdraJn

10.4 Coronal Sections: VII and VIII

I.Gnglludnal Cll!n!bral IIBYn!

- - - -+----;t....__

_....::!!:.r--~::::::!!p

ln!Jemal capsl.fe.

postsforlimb

Cl~ --~;;::----::=--=----­

nucleus, ta1

Tllallmus. puMnar

Cerebral

aqueduct

A Con1111hectfonVII

Among thediencephalic and !!!lencephalic nuclei, wecanst11 identifythe thalamus and ocdplt.11 portions of the c:.1udate nudws, wfllch become progressively smaller In tile following sections until tlleoy flnillly clsappear (seeCandp.lOO). Theocclpttal partoftllehrppoarmpusc.mbeseenbe· low the medial wall of the lateral ventride. Thi$ section cub the brain· stem along tile c:en!brol aqufduct (see C). The cerebellum Is conne<:ted 1» the braln.stem by three white-matter sulks: tile supedor cmbfllor Pft/um:k (mainly e!ff!ti!Ot), middlr ~lar Pft/unck (afferent), and ln{mor ~ ,mmde (afferent and efferent). Bec:.1use the mrddk

I Cerebellar pecllnlfs on the bratnstem a Postl!rlorW!w, II lateralllfew.

298

cerebellar peduncle extends further anterf011y tllan the ot:ller two peduncle.J (note in relrtionship 1» the brainstem axis), it is the first peduncle to appear In this front.11·to-oc:dplt.11 safes of sections (see also A. p.296, andD,p.297). Thesupedorc:erebellarpeduncle begins on the posterior side of the pons and til us appears In a later section (see B .and p. 300). There a reno natural anatomical boundaries between the middle and Inferior cerebellar pedundes, and tllerefore tile latter Is not separmly labeled In the sections. The supertldal veln.s were remCM!d from the brain wflen tilis section was prepared, and only tile internal cerebral veins appear In this and tht'followlng section.

Longltucfllil------.=~-~;------'~--~

urebrlllflssure

Choroid plexur.

oflamaiWirtrfde

QLUdrlgemlflil plat!!,

superlorcdllrulus Cerebral aqueduct

Choroid plexur. offourt!l ventricle

c

CoronaltedtDnVIII The thalamk nuclei appe;~r smaller than lfl pmtlous sections. arid more oftfte cerebellar cortex Is seen. This plilne pii!Sses through partofthece· rebralaqueduct ThedwJm~(ossa,'Whlchformsthefloorofthefllurth ventricle, is clearly visible in the dorwl part of the brainstem (seeD and 8;1). The quadrigeminal plate (lamina teet!) Is also visible. Its s!Tiilller sttperlorcollfcull are partlaJiarly well displayed lr1 this section, while Ute f.n/e11crcolllcull are more p~lnent In the next section (see A, p. 300). The pineal is only partially visible because of iU somewhat more occipi·

tal location (see D); a full aosHectian can be seen in A, p.300. The present section shows the diYislon of the paired fllrnht tract Into Its~ auro (see also D.p. 295). The hippocampus here borders on Ute Inferior hom oftfte lattr.ill ventricle or1 eKh side, bcJiglllg Into 1ts floorfrorn the medial side (see also the previous sections and E). The hippocampus Is an Important component of the Umble system arid Is one of the first struc:tlJre.s to undergo detectable morphological changes In Alzheimer's disease.

Posterior _ __:.f-,-......;:- ....:..J,.Hiiiiir- - PfnNI c:omm~re

Cen!brlll aqueduct

!.......#-+--

"""=""-

l'e(foot}of h~~mpus

l'lllneofsectlan - - --f

InC

D Midsagittal sectt:Dn through tfle rhDmbenCIII!phiiDn,

mesenoeph•lon, •nd dlencephllcm

E HlppoamptlformiUDII

Left late<"al view.

299

10.5 Coronal Sections: IX and X

Lon~ltudlnal

«nbr.JI fli:sure

- ---.--- '\o--- ----'...,.._-------.1.

Li-~i!----"<---!~-=:=:<.::::::!::'.:--

!a!ralventrlde, a!ntr.llpart

Quactfgemlnal plate. lnfufarcdllwus Oenlatl!

- --i?---__;_ _ __

nucleus

Un!belar wrmls

A Gel ronal sectiDIIIX

The plneiil gland. a control cenrer for clrcadJ;m rhyttlms, IJ here dJJ· played In full aoss-sectlon (contrast with Ule previous section: see ilso D. p. 299). Below It lle.s the quadrigeminal pliltl!. the dorsal part of the midbrair\ (note its relationship tD the brainstem axis). The larger inferior colllcull of the quadrigeminal plate are more prominent here than In the pre1ltous section (the lncllflatlon of the brilnstem gives them 01 more posterior location}. The fn{l!tfor colllcurr are part of the auditory p.rthway, while the s~ CDJiiculi (more clea.ty seen iA the previous section) are part of the visual pathway. At. the level of the cerebellum, the 11m11Ts can be ldent:lfled unpaired midline structure. The only cerebellar n~~eleusllfslble at this level Is the den !Db! nuclells, 'Which Is surn~Unded by the cen!bellarwhite matter. The deep cen!bral nudei are no longer visible In the plane of this section.

as""

l..'lteral genl111late body

llledlol

geniculate body

B Qulldrtgemlnll plate (lamTna tl!cU) Left posterior oblique view.

300

IAngltudiMI

- -.....,.,:::l...- P..---.....;:;;...__ _-:1.

~lftssun!

Dllntate------!,....-''--- -.:.;_nudl!us

c

CoronaiS«UDnX

Thi$ plant- presents tht-four ~lor nlttlri: • Denta1z nLJCII!I.Is (lateral cerebellar nucleus) • Emb~llform nucleus (anterior lnte~posltta nucleus) • Globo5e nucleus (posterior lntuposltus nudws) • F.astlglal nucleus (medial arebell.ar nucleus) The longitudinally cut cmbf!llar 111!1!111s pre.st'nts a larger arN here than iA the previous section. The fDurth wntricle is no longer visible iA the plane of this se<:tfon.

301

10.6

Coronal Sections: XI and XII (Occipital)

~-----!c.__---,J.---

tmnlwniJfdt..

oc:dplbllhom ....-l~-+----->...----,.,..,1---

Anterior lobe

ofanblll.lm

l'cllllmrlobe d~belhm

Qm.ff•rwnnls A c-al HdlanXI

.....

The planed this section cl9rly sh- the posterlor (occipital) horns of the !Ural venb1da; these appar only as narrow sflts In the next section (see D). The section also illuslr.ltes on~ again how the posterior horn is il prolongiltion of the lrrfenor (temporill) horn {see I). Between the cerebellum and the oc:dpltallobe ofthe anbrum lies the tmmrtum anlleiiS (see C). The tentorium contains the straight sinus, which p;~sses to the confluence ofthe slnuMS. It Is one of the durillvenous sinuses thilt drain blood from the brain, beginning at the c:onftuence of the great cerebral Yeln and the lrrfenorsaglttal sinus (removed during preparation of1he fa be cerebr1). Beeo~use the dura Is removed from the brain In the prep;~­ ration of mort ti!OSue sections. the sinuses enclosed by the dura mater illso tend to be removed.

Agltllolllnus

SLpOIIor

~·

sinus

~~~~1~~J-+--s~~ sinus

Ocdpltll

hom

lln!Drium ..a~r

C Tbe durilhlnuVIewed from upper left.

302

D Coronillsec:UonXI In the plar~e of this section, the postel'for (ocd'pltal) horn of Ule later
/"'"', ..,...--- Pllneofsectlon lnD

E Rfght ttrfltUI'H {VIIull corta) Medial surface of the ftght hemisphere, viewed from the left side.

303

10.7

Transverse Sections: I and II (Cranial)

~-......::._---~-- tmnlwftlrtdl',

11111S1or hom

~-..,..------=-~:,.--..---

Lmtwlwntride,

..nt.. ~rt

~...,_--'---'---'---.----.:::;_:....;.._

_

lalgltudlnll

..te~~..l , .....,

Gener•lrem~rt&sontr•-br•ln lledlo•

A Tr•-ne lldlon I

The sections In this series are viewed from above and behind the held; i.e.. the obser.e"is looking at thuurf~ce orthe slice as itwould typi~lly ilppen In a brain autopsy or dur1ng il neurosurglc.al operation. Thus, the left side of the brain appears on the left side of the drilwlng. This contruts with the imilge orientlltion in CT and MRI, where brain slices are iiiWi)'s viewed from below; I.e., the left side of the brain appears on the right side of the Image.

This highest ofthe trilnsverse brilln sections p;mes through fronbll, pi· rietal, and octipit.11 structures of the telenceph,lon. Each ofthe two /lltrtVI wniTides Is bordered literally by the body of the caudate nucleus, and medially by the trunlr of the mrpus mllosum. The corpus Cilllosum tnlnsmits fiber truts whith intwconnect anlis in both hemispheres that serve the Silme fu net!on {commJssurcrllnleb). When viewed In aoss section, the corpus c.allosum appears to be lntemJ ptl!d by the venb1cles and uudate nucleus, when, In fact, It arches over these structures, fonnlng the roof of the literal venblcles. The course of the tracts that pass through the corpus c.allo:su m an be appreciated by looking at a coron•lsectlon (see 1).

304

NeuiVCIIKIIumy -

10. SectionaiAnatrJmyoftheBrvin

~~·~•~urn.------~~------~-------;~

genu

.Stptum ------~----::::J.--~-------:-...:f'­ ptll~m

Corpus calasum, trunk

1-------------------..,....--l.:.....- - loi'Qitudlnal

conlnlfllsu~

C Tr-IM lldiOIIII

rt Is antertorty con\IU. The diagram In Edemonsmtes why this sectlon

In this section. unlikr the previous one, the lutmi/ -~ appr.;~rs divided In two. Bea use this sectlon Is it i lower level, It cuts the an• rior and posteior homs of the IntraI ventricle separately, missing the centril JNrt of the ventrlde (see D). It also cuts a broad swath of the lnll/mo/ ~ v.tth Its genu and anterior and posterior limbs_ The optfc radiation, which runs in lfle white matter of the ocdpitallobe. is not labeled here beause It has no grossly visible anltDmlal boundarfes. The CIJiliiiS m//omm ~lso ap~rs diVIded Into two parts: the genu anteriorly and the trunk more posteriorly. This apparent division reJUits from a second curvature of the corpus callosum at Its genu ("knu"), where

p;~nes sucxes~ly through the genu of the corpus nllosum, the

Genu l'oltltrtar

sep-

tum pellucldum, the body of!he hlmlx, 1nd fln~lly the trunk oftfle corpus callosum. The septum pellucid urn fom\$ the anteromedial wall of both lateral ventrldcs. The septum Itself contains small nuclei. Seclions oftfle thilamlc nudel (wntrallateral, Literal dorsal and antertor nuclei) are also visiblulong wilfl the putamen and caudate nudeus. The head and tall ofthe audaten ucleus appr.;~r separately In th section (see also ~The pubmen, caudate nucleus, and lnti!M!IIng ftbers oftfle Internal apsule are collectiwly ulled the corpus strlitum.

-;,C....-::::;===?-==-""'=:P"""'o::~- PIIMOf-=tlon InA -4-~4-W-rflf:.=:......::::......=--;::...~- Plan~~ofsodlonlnC

Splonlum

hom

305

10.8 Transverse Sections: Ill and IV

LDngiNdtlal

----=-------74--~.,.------'-2---i

atrelnl ftl&lft

lnttmal capsule, 11(15Wrtcrlimb

Charoldpl...,s

of lnerel1lel'ttllcle

A Tl'iiiiiSWIU lledlon Ill The later~ I ventricles communieilte with 1he third ventricle through the ln!lmntrlatlorjWvm/no (of Monro). They are IOCii!Ed directly anterior tD the thalamus (see D, p.. 305, and A, p. 296). The nudel of the telencephalon mak2 up the deep gr.JY miltter of the cerebrum. The spatial relitlonshlp ~en the audm nucleus and thalilmus Is lllustrall!d In 11. The caudate nudeusls larger frontally, and the thalamus larger occipitally. While the caudate nucleus and putamen of the motor system belong to the telenceph1lon, the thalamus of the sensory system ~ longs, tD the diencephalon. This transverse sedion passes through the caudate nudeus t'Mce due to the ilrutom IaI a~rvature of the nucleus. This Is the flnt tra nsvene section that displays the globus pallldus, part of the motor system. The lnsu Ia r cortex Is seen with the doustrum medlill to lt. The 01/IU af the fomb« are seen iiS posllerlor to the thillilmus (RuiiCI E. p..l05). They unite ita slightly higherle-..el to form the body afthr (omlll. whkh lleJ just below thecorpus callosum and Will visible In the prwlous section (see C, p. 305). The course ofthe lntemill apsule Is visible in bvth this section and the last.

306

8 ~ln~liltk!Mhlp~ofthl caudal nuc!M1. putllnwn. thalamu1. ancllabnl wntrtda ~anterior oblique view.

NeuiVCIIKIIumy -

10. SectiomiiAnatumyoftheBrvin

Globus polldiS,

lm!rol H91'M'"t

caJclmrv.JdWS. --.C::::=~~---1:111 Intern~I apsLi~. posb!rkrllmb

Charald piOlUs ofl~lwntrlde

C

Tnnswrse setUDIIIV

Th~ nudei shown in th~ previous

sec:Oon here appe.~ r as a roughly cir-

culir mil5s at the center of the bnln. surrounded by the g rq matter of the cerebral cortex, also ca lied the pol/tum ("ciDik") for obvtous reasons. The chorllid pleJws iJ here visible in both lateral ventricles. This section cub the occlpltiJI pi rt of the corpus callosum, the !plenlum, il5 well as the b;Jsal portion of the tnsulor IXII1l!!X. The lnsu L1 Is a corUG'~I region that lies below the surface and b covered by the opercula. The Insular cistern should be used iiS a refertnce point, e.g., when compir1ng this section to A and D.

D IAift ln1u~r 11151ID11 l..al:l!ral view.

307

10.9 Transverse Sections: V and VI (Caudal)

~~~----~------~-L1_~ Opllcl..ct ---~~---_..:::::::::::~~

lhlnhonll1de, aptiCrKea

------:::r--------,.....,.--!

Corebril podund& _ _....:....--...,.>-----'-'f-- - t "

Conbr;ol

(CJ\IS....,n!bli)

,_,a!()hilon _

aqueduct ___.:._....>...,,..--:--,----=---.l!:i~---(

M~~~ -~-----_;~--~~~ genkulm body

~~----~==~-----~

C""~...,.\---..::.--~L-

gonlculall!body

Hlppoc~mpw

Vlnnllof _

_

....,...._ _;;,__ _..;;

arobolum

Ah-5KdonV

5tnlc:tures VIsible In this SKtfon Include the c:erebm :~queduct, the basal part of the third ftlltride (see •Iso I, p. 294), and the optic ~5S. While the third Yentr1cle Is slltlllat It this 11¥11, the section cuts a very large area of the ventricular system whe~ it opens into the two PCI$telfor horns. This Is the flrlt tr:~nsverse section thlt displays the midbrain (mtlilllr:wpilalon), passing through Its or.I portion (110ft: terms of location and direction refer to the br:~instem illCis, see p. 198). The cerebr.l peduncles (m1ro cmbrl), the Sllbmlntlo nlgro, and the superior collla/U ofthe quadrigeminal platle an also be seen. VlslblestnJctures of the ~ encepho/on In this plane lndude the l1lft!krl and /amu/ gmlculore bodres (appearing only on the right side, see I) and the optic ttvct, which Is an exttnsion til the diencephalon. Mn: closely ildjacent st111ctures In the brain 111i1Y belong to different ontogenetic regions. For exam pie, the mediiI ;md IatenI genlculilb! bodies are part of the dienc:ephillon, while the superior and inferior c:ollic:uli (the litter Is not visible), which malat up the quid llgemlnal plate, are p;rt of the mesencephalon. It should be recalled, however, that the later.Igenlcui;(te body and superlorcollku Ius are part ofthe vtsu;ll pathway while the medial genlculatle body and Inferior colllculus ire part of the auditory pathway.

308

Qwdngomln;ol plabe,

wportor.,d nferiorcDIIk:ull

B Pant, mldllnln, 1nd IIIIJMB1t dlltnmphlllon ~ PQsterior obi iq ue view.

Neu.rva.nalumy -

OaJomou.. -----......:~:__ _L

..w(OIIIQ

10. SectionalAnatumyofthe Brvin

____

Pes (foot) Gfhlppoamj)IIS ---+---:-----+--

Choroid plexus of lattnl vontnde

ty;;...:;_-'"'~....,.....,...........-

-

Lmral~
posbllor hom

C T,._netediOIIYI

The slructllres thlt oa::upy the llrgut area It this 1-1 ;are the telenaphalon, the medial portions of the me.~enCephalon, and the cerebellum. The nudd loclled on the median ~~pect « e;ad! front3llobe of the tl!lencephalorure the Cllll)9dalae. The IO'M!!r part ofthe section cuts the m/arrine sultuswith the surTOUnding visual cortex. This section also p;asses through the dlorold plexus of the lilttnl wntrldes, wh05e poslzrfor ~nd ln(lrlor lloms ~re displayed. Impo~nt structures of the m~ ~ •re the JUbsuntll nigra and red nucleus, both of which are part of the molllr systl!m. The mammllllry bodies iln! part of the dlen«'JJ##O'/on and are connected by the fornix (not visible in this section) to the hlppoCiimpus, which Is part of the telrnaphtJioo. The mammillary bodies Ire In the same horllOOUI plane u the hyppoCiimpus iind the same coronal plane as ib pes (foot). These mationships result fnxn the curved shape of the forniK (see D). More tnnSYII'Se sections It lower levels wauld supply little additiGnal infcum:~tiGn Cll'l the utebrum, and so our series of tr1nsverse sections ends here. The br.ilnstern structures lying below the mesencephalon are dlspli)'l!d In • separate group of sections (sre p. 234, 2l5).

Hlppoampus

D ramlx

Left anterior oblique view.

309

10.10 Sagittal Sections: 1-111 (Lateral) lnsut.

•

Plrohlppocompal

!D"'•

A S.lttiiiKIIoll'l 1-411 left l~enl YII!W. The plane ofsection 1 paiS1!S th rGugh the ltrfMot'(IJ!m. pwul) hom of tile lateral ventricle; the mo~ medl~ly sltwted postmor (~ hom Is seen In II and c (see C. p. 296 for relative position of both homs). TheO'tll7!l'do'/cl, whidl is di~ctly ant.rior to the infl'riorhorn, lies In the same saglttll pllne .s the parahlppoampill gyrus (ii-C: see also C. p. 309). The Internal upsule un also be seen In sections ..c; the l1111g aS«nding •nd descending truts piDs through this structure. The most lateril section (i) olfws the only lllaw of the lnsu/Gf awtu. a part ofthe cerebral corW.that has sunk below the surface ofthe hemisphere (compare wltll thec:oronal sections on p. 293 ind the following pages). The putumen. the most laterally situated among the basal ganglia of the telencephalon (see also A. p. 296) Is also found in a. but appears larger in the more medlill.seclfons (b. c). A portion of the doustrom an be seen

310

Wl'ltral to the putamen (a), although most of the dausllum Is 1Ma31 to the putamen (see A. p. 297) and outside the plane of the section. 5ec:11onlitjust alb the taU of the cuudatr IIIICiela, which ln ltwted more literally than Its had and body (see also D, p. 279). The most medlalsec1ion inthi$ series(c) cuts theOJic::&Jrint sulcU!S (see p.312)and thelc!ttrlrl Jjllllal.lolr body which lies ~ tile edge of the thalimus. The lateral segment of the globus pallldus an also be seen (c): the segments of the globus pvltidus ue actually mecfNtl to the putamen (see D. p. 295), but an be lllsu;lllzed here due to their conc:entJk arringement.

Neu.rva.nalumy -

10. SectionalAnatumyofthe Brvin

Ambrllld hWCDmP"'

Lmonaflnsula lnll!mal

Cllpsule

b

Puhlnr. tholamiB

Cakarine sucus

GlobLapollld"" _ _;~~-+-------­ labtllll >egnent lntanal apsue,

antertor l'mb

Prt....rytls:sui'O

Floaulus

c

Po5terlorlobo of a!I'Obollum

311

10.11 Sagittal Sections: IV-VI

~

ColpLa

apsull'

allooum

PUMrw, INIIITVJ!I

Clla~ne

Julcus Anll'rlorlobe

ofcerebelum

_,_.......l....---'-T-=--=--- I'IIIIRrlor lobe

ofcartbelum

•

A Seglttal sedloM IV-YI

Left ~I Ylew. The dominant wntrtcular strucll.ues In all thlft of these sections are ltte anta11or horn and afttral part ofthe lamulll!lltrJ. c/r (the junction with 1he laterally situated pos~rior hom appNrs only In a). The curpus collcaium, which connects functionally relmd areas of the two cerebral hemispheres (commi$sural tract), can be identified in the cerebral white matter although It Is not sharply dellnealled (a-c). As the sections move closer to ltte cerebral midline, the putamen graws srmller while the c;~udltt nudeus becomes inaeasingly promiment (a-c:). These two bodies are known collectlwly as the aliJICIS .st71aturn, and their charactertsUc strlaltol'ls are s.n particularly well In a (the white matter that sepanltel the gray-miltter streaks ofthe corpus striatum Is the fnlwnal mpsu/1). The previous uglttal sections showed only the latera Isegment of the globut pai/Sdus (see p.l1 0), but Its media Isegment Is displayed In both • and b. As the globus p;~llldus diA ppea rs and

312

1he putamen becomes less promintnt. the nudti ofthe medially situated thalimus bec:ome visible below the la~ral wntrkle (c: the subthalamic nuclellnducle the anterior, poslal1or, and lateral ventral nudel oflttedlmaphalon). The location of the thallmus explains why it is sometimes referred to u the donG/ !tlalarrM. Section c: also s ' -the substonltG nJ. Ill"' in the mesencephalon (below the diencephalon), the inferior olivary nucleus In the underlying medulli oblongata, and lfle drnm~ nucleus of the cerebellum. The asctl'ldlng and desaftdlng tr01cts previously 1115ible only in the internal capsule c;~n ncrw be seen in the pons, part ofthe bralnstem (c, corticospinal tnct). The only visible portion of the fourth wntrlde, barely setUoned In c, Is Its lateral receu.

Neu.rva.nalumy -

lntem•l . .ulo. g .....

10. SectionalAnatumyofthe Brvin

Corpus aiiCDUm

CNsaffomll< l'\llvlnor

~rlobe

ofanbeii.Jm

a>mmlssun! Cllobus pallklus, medial segment

~.,---=:1~!1---.--- Pomtlorlobe

ofanbeii.Jm

~ } HD
nudtus

Tbilomlc nuclei

Coucllll! nuclous, had

Slbehllilmk: nudtus

Prtmoryflssu"'

Jnf'afor obwrynudell$

c

Post2
313

JO. SectionalAnatomy ofthe Brrlin

NftnuarKltvmy -

10.12 Sagittal Sections: VII and VIII (Medial)

l'llillimkrudoi

CJ1rpuocalla11.m, gi!I'AI

CJirpuoc:ollaoLm,

_____

--+----',.,__,~..,_

rastrum

~:4iliiii:::-::--Jr._:~"f.__ -~ Df
lnfwtlor calllalus

Supeflcranbolla-

pedunclo

• A S.nt.l Mdlv• V11nd VIII Left laterllllllew. Thls .s«Uon (e) Is sa dose 1D the midline !hot It p<~sses thnlllgh the princip<~l par<~mfdian structures; the substantia nigra, the red nucleus, ;md one eadl of the paired wperlar and Inferior mllkull. The pyr.~ midaI tract (cartfcospinal tract) runs in front of the inferior alIve In the medull1 oblongata. A completE s.~glttal .section of the corpus callosum Is dlspla)'l!d, lind most of the fornix met Is displayed In lon-

314

CBebolor IDnsll

glllldlnal section (b). The cerebellum has readled Its mulmum extatt lind forms the roof of the fouf1fl Wl'ltrlde (It). A portion of the septum

pW/ucidum, which slletch~ ~en lfle fornix and COIJIUS callosum, is also displayed. When the brain is removed, the pituitary gland, which appea 1'$ in b. remains In the lei h1 turdca: l.e.,lt Is always tam from the b111ln a Its stalk when the brain Is removed.

Neu.rva.nalumy -

10. SectionalAnatumyofthe Brvin

Septum

pdluddum

n:--4~--==-~~- Quad1gemlnal plate Anl2ftcrlabe ofmm..llum

medularylnr..tor velum

/

Medull abklr9ta

/

Cettnl aonal

B Pmdp;~l stnKturBin the serlill sediDns The major strudlrras seen In the serial sectklns

are here 1ulgned tu dlelr corresponding brain regions. Within each region, the structures are limd from most rostral tu most a.udal,

~

TelenCllphllon (endlnln) • Ex12mal capsu ~ •

UvUo

Nodule

i'

~apsule

• lntemaI capsule • Claustrum • Anterior CDIT1mls1Ure

Dllrlaephllon (TIIblltwaln) • ~I genlculola body • Mtdllol gl!f'llculite body • P1nul gland • PuMrwr of thalomus • Thalamua

• Amygdala

• Optic tract

• Corpus callosum

• Mlmmilllry body

• Farnbt • Globus JNIIldus

.._ne~p!Mion (mldllnln)

• Clngulite gyrus

• c:..bralaquaduct

• • • •

• Qwdrlgomlnal plm (lamina t.ctJ) - SU~orcoiiJculus -lnlllfor colllculus

HIJIPCICilmpus Ciludilbe nudeus Put.ilmen Septum pll!iludckm

• Rednudeus • Subob nlla nigra • c.-brill peduncle (crus cenblf)

315

NeurDGnatomy - - 11. Autonomic Netvous System

11.1

Sympathetic and Parasympathetic Nervous Systems, Organization

Parasympathetic ganglia (In the head)

L.acl1maland salivary glands Cranial wssols

Parasympathetic ganglia (close to organs)

'Stellate ganglioninferior a!Mcal ganglion and T1 sympathetic ganglion

Lung Stomach

I.M!r

Pancreas

lntesti~

Supel1ormesentertc ganglion

Parts of the colon, roctLm

Bladder Genlllllla

Samlpart: sacral cord with } parasympathetic nuclei

lnR!rtor hypogastric plexus

A structure ofthl! autonomic nervous system The portion of the nervous system which Innervates smooth muscle, cardiac muscle, and glands Is called the aU!Dnomlc nervous system. This Is further subdivided Into the sympathetic (red) and parasympathetic (blue) syrtems, each of which has a two-neuron sequence between the CNS and Its target, consisting of a presynaptic neuron In the CNS, and a postsynaptic neuron In a ganglion (PNS) close to the target organ: • Sympathetic system: presynaptic neurons located In the lateral horns of the cervical, thoracic, and lumbar spinal cords. Their axons exit the CNS via the ventral roots and synapse with postsynaptic neurons In sympathetic ganglia.

316

• Parasympathetic system: presynaptic neurons located In the brainstem and sacral spinal cord_ Their axons exit theCNS via cranial nerves and pelvic splanchnic nerves to synapse with postsynaptic parasympathetic neurons, typically within the target organ_ The sympathetic and parasympathetic systems regulate blood How, secretions and organ function, often acting In antagonistic ways on the same target (see C)- In the abdomen, small clusters of neurons embedded In target organs form a network that can be considered a third autonomic dMslon: the enteric net110us system (see p. 324). Although this network receives some presynaptic parasympathetic Innervation via the vagus nerve (CN X), It typically functions Independently, responding to local reflexes.

Netii'OIJnatomy - - 1'f. AII!Ditomlc Nfi"'IIUS Symm

B SynlpUc Gf91niHtTon aftM 1uc-m1c nervoussymm The sym~tluroc and p~raJympathetit porti~ns of the nervous systems innerYate many of the S<~me t~rgets. but use diffa'ent tr.msmltten, often with antagontsiSc effKts (see C). These 01nugonlstlc systems also hiM! dlffe11'ng p.rtterns of o~anlz:ltfoll, llldudtng unique paths m thefr ta~eb ind Cl:ll'lnKtions to the CNS. The cell bodies of the presyn;rptic motor neurons of the qmpll'lhctk system ~re lotated In the lateral hom of splllill cord segments T1 to L2 (sometimes C8 ;md 13). Their axons IHW the splnil corll through thoracolumb.n ventr•l roots, briefly ttavel in spinal nerves, and enter the paravertebral sympathetic trunk via white rami communlcantn (white -myelinated). These axons terminate In syn.;~pses with postsynaptic neurons atUiree different lewis: Wh~r~mus

1. Sympathetic gallglla along the paravertebral chain: The postsynapISc neurons send their aXDns biKk Into the spinal nerYeS vta gray r01m1 ccmmunicantes {gray - unmyelinab!d). These axon.s b'awl in the spinal navn to lnnerYate local blood wssels, sweat glands. etc. 2. Prevertebral sympathetic ganglia: These gangllor1 cells send thefr axons along arterial plexuses m the bowel, lc!dneys, etc., pl'lMdlng inrll!rY.ation m both the organs and theirvasculawre. 3. Adrenal medulla(not shown): Adrenal medullary(endocrfne) cellnre development
communlans

P~ Ventral root

Vl!n!r.ll ram us

- - S)m(lllhel!c ganglion

~'m'er~Jebnll

g111glon

lnlnmu111l neuron

In contrast, the presynaptic neurons of the pal'llsympatfletic: systl!m are located in the CNS in the brainsb!m (crinial nerves Ill, VII,IX, and X) ~nd si!ml splml cord (S2-S4). The pre.synaptlc alUins lea~~e the CNS via the cr;mlal nerves noted ibove (the vagus neNe (CN X) Is the e1101mple shown here), and pelvic splanchr~lc nerves. These pre.syn•ptlc axons synapse with postsynaptic neurons in discrel2 cranial ganglia (ciliary, pterygopalatine, submandibular, and 01k). wlllch lr1 tum send their axons In other aani;!l nerves to the target organ. Some pre.synaptlc axons, p;utlcularfy the vagus nerve. Innervate scatl:2red postsyn•ptlc neurons that are embedded in the target crgan.s themselwes. Afferent flbers (shown In green), originating from psaxlounlpolar neurons In spln
C Synopsis af tile symp;ll:hetk ;~nd p~~rasymplthetk nC!I'VOIIs systems

This table summal'iu$ the efi'ects of the sympathetic ~nd parasympathetic nervoussystems on spedflc organs. • The sympaltJetknavouuystem Is the exdt· 01tory part ofthe autonomic nervous system (tlght orftlght). • The(Xlrosymsxrthefic nervous S)'Stl:!m coordi· nates re.st ind digestive processes (rest and drgest). • AlthccJgh the two systl:!ms !me separate nuclei, they es;tablish cl"'e anatomi~l ~nd functional conooctloru In the periphery. • The tr.msmlttentthe target organ Is oc:et)1chcf1nt In the par~sympathetlc and 11011!f11nephrin~ in the JYmp~thetic llC!IVOU5 syJtem (elaptfortheidrt:nal medulla). • Stimulation of the sympathetic or parasyrnpathetic nervous system produces; the fol· lt!Mng effects In specific organs (see table):

.....

Orgln

,...,.......,_

l'iii'I'VIllpdlltk-5JIIilm

~

Pupillary dHatlon

Pupillary constriction and Increased

Sallv.lry glands

Dec:rftsed sallv.lt!on (sant.. viScoUs)

HNrt

Rise In ~rt~te

F~llln heart rate

Lungs

Dec:rftsed bronchial secretlons and bronchoddat:lon

Increased bronchial secretions and bronchoconstrtcaon

r.astrolnb!s!Sn.al tract

Dec:rftse In secretions and motility

lncrNSe In secretiOns and motility

curvature of tilt lens lncrNSed salivation (copiOus. watery)

P~n~s

Dec:rftsed tlCIOCrlne ~ons

Increased exocrllle secretions

Mall! sex organs

Ejaculation

Erection

Slcln

v-nstlfctlon, -ang. piloerection

No effect

317

11.2

Autonomic Nervous System. Actions and Regulation

I S)'lllprtt,ellc - -

ganglion

I

~ --Mtylcl10llne

Aat)ict!ol'ne - -

A Clra~lt dliiQI'ilm of tile autonomic Mf'VIIUS system The centr.ill tlrst (presynaptic) n~ron uses .ilce~hollne as a lrilnsmitb!r in both tne sympathetic and P.ill'iiJYmp~thetic nervous JYS· ~ms (cholinergic neuron, shown In bl~~e). Acetylcholine Is .illso used as a neurotr.ilnsmll:tl!f by the second (postsynaptic) neuron In the p.irasympathettc nerwus systl!m. In !he synnp.itlte!fc nervous system,

- - P;u;n)'npdu!tft ganglion

noreplr~ephrlne Is used by the noradrenerglc neuron (shown In red). Nob!: tne t.ilrget cell membrane conblns dtlli!rent types of receptors

(• transmitter sensors) for ac:etylcholine and norepinephrine. E;!ch transmltteB c.1r1 produce entirely dllli!rent effects. depending or1 the tvpe of receptor.

Umlllc

symm

Emotlonll diM

Homeo:stzlls

....................... ~

. . . . . . . . . . . .L Splnaln!llexrs

- - - -- - -- - - -

------------------B Control of1M perfphel'ill autonomic nervouuystl!m (aftef Klinke

through centers lr1 the hypoUialamus. medulla oblong<~t.il, and spinal

.ilnd Sllbemagl) The peripheral actiam of the autonomic nervous system are sub· ject to cor1trol
cord. The higher the control center, the more subtle .ilnd complex Its

318

elli!ct on !he target organ. The limbic $Y5tem ~il/e$ sign;~!$ from its t<~rget organs via afferent feedbi!dc mechanisms.

Netii'OIJnatomy - - 1'f. AII!Ditomlc Nfi"'IIUS Symm

Spbal
®{

}®

hypo1N~mus.

affilrilllehen'/a, rupl~ryneu~ns.

r!!ielnPco,

e

Pluloreaptan;

e

• ~ neurons

Meduh oblongata

~ry

neurons Symp.athoexdt.ltary ne~Jroru

~

SoltMy tr.lct

C Elcclt;l1;orywlnhlbltoryetredson sympatfloexdtltory neurons In tfle medulla oblongata a C~ctlon through the bralnstem at the le...el of the medulla oblongata. To generate a baseline lew! of symp.athetlc outflow, the presynaptic vistl!ral efferent sympathetic neurons In the spinal cord (lntermedl~ lateral and lntermedlomedlal nuclei, see p.271) must be stfmulated by sympilth~ excitatory neurons in the anterolateral part ofthemedullaoblongata.Numerousf.lctors can Inhibit or enhance the activity of these neurons ~lch play a crttkal role In the regulation of blood pressure. If the blood pressure Is too high, for example, afferent Impulses from the pressoreceptors wtlllnhlblt symp.athetk outflow. b Afftrent impulses from the facmn listed Ina are relayed In the medial nuclei of the solitary tract nucleus to secondary naJroru. 'Whose .uons project b.ildcm the sympath~ excitatory naJrons. When these neurons are Inhibited, the peripheral resistance vessels relax and the blood pressure falls. The axons from these sympathoexdt.iltDry neurons pous ipsi1;tterally through the poste~ lateral funiculus to presynaptic sympathetic neurons rn the lateral hom of the spinal cord. Sensory neurons are shown In orange. motor neurons in green.

b

319

11.3

Parasympathetic Nervous System. Overview and Connections

A OWI'VIII!w: parasympatheac MNOIIS systl:tn (Ctllnlel part)

Cllary gangllcn

There ire four paril~ympatftetlc nude! rn the bralnstem. The Vl~ceral efferent fiben of these nuclei traw.l along particular crinlal nerves. listed below. • Viscefil oculomotor (£dlngerWe~tphal) nucleus: oculomotor ne!Ve(CNIII) • Superior s;~tavatary nudeus: f.lcial ne!Ve(CNVII) • lllferfars;~llvatorynudem:glosso­ pharyngeal ne.ve (CN IX) • Dorsal vagal nucleus: vag ~a nerve (CNX)

'\ l

1____--"""'-.c=f_

1/lsar;ll oculcmotor - - - - • \

(fdnger-Weslph;ll) nudeia

~--------------5~

mandibular ~ion

The presynaptic p;~rasympathetic fibers often travel wlth multiple aanlal neNeS to reach !heir target organs (fer details see p. 31 and E, p. 85). The vagus nerve supplies all of the thoriclc ind ibdomlnal organs as far as a point near the left colic flexure. Note: The sympathetic ftben to !he head travel illong the arteries to their target organs.

B Paruympatfleac g~nglllln the hMd

.......

Nudaa

Nhofp..,.......cflllss

r.ngiiDn

~lciiiBs

~

• 1/isar.al OOJiomotor(lidlnger-\\fHt. phaOnudeus

• OC11Iomotornerw.

• Ciliary ganglion

• Sllort ciliary nerws

• Ciliary musde (aa:ommod;rt!an) • Puplll.arysphlncter(mlosls)

• Malllary nerve -zygomatic neM- aNI!tomoslslaafmalnerw

•

•

Super!ors;~llvii!Diy

nucleus

• Nervus rrme~medrus (fa~l nerve ~ot) dMdu Into:

~crtmal gland

• Gremer petnosal nerw. -+ nerw. of pterwOid anal

• Ptzrygop;ll;rtlne ganglion

• • • •

• Chorda tympani -nngu..lnerw

• Submandibular ganglion

• Glandular br.anches

• Submandlbulargland • Subllngu..lgland

Orblt.11 brilnches Latef.al f)OStleflor nasal branches Nasopalatine neM Palatine nerves

• Glandsan: - f)OStlefiOr ethmoid cells - nasal conchae - armerlor pal.ate - hard and soft palate

• Inferior sar.v.~tory nucleus

• Clossopharynge.al nerve -tympanic nmre -les:ser petrosal nerve

• Otic ganglion

• Auriculotemporal nerve (CN v,)

• P.l!11tidgland

• Dorsal vagal nucleus

•Vagusneflle

• canglra near organs

• Ane fibers In organs. not individually nilmed

• Thoradcand abdominal visar.a

-+ -

320

Is continuous with

Netii'OIJnatomy - - 1'f. AII!Ditomlc Nfi"'IIUS Symm

C Ow Maw: p;IIIIJYIIIpllthl\lc MI'VOClJ sylltam (lumii1'0NC.11111 p;~rt} The portions of the bowel near the left colk flexure ind the peMc vis· ari are supplied by tile sacral part of!he paral'JIT!pathetlc nervous system. Efferent fiberseme~efrom the anterior $aCral fvramina in the ven·

tral roots of segments S2-S4. Theflben ire collectl!d Into bundles to form the peiYic splanchnic nerve.s. They blend wfttt !he sympathetic fl. bers and synapse In the ganglia In or near ttte orgaru..

Hypothllamk

tuberal nuclei Mlmmllary

body

VlsCS'II oculomatllr nucleus 9.1p111Dr

saiMitarynudeus

lnfafor saiMitarynudeus

Danai

D Connlctlons of the dorAIIongltudbll f.lldc:UuJ Increased $i!llvatlon during t'itfng results from stimulation of the s..l11/ary glands by the paral'JIT!palhetlc n~ system. To produce the coordln<~ted stimulation of various glands. the crinlal parasympatiletk nuclei require exdtatory Impulses from higher cenl:efs (tubefal nuclei. mammillary bodies). The paral'JIT!paU\etlc nude! are !hen stfmulated to increase the 11- of saliva. The donallongirudinal fasciculus establishes the neC6$i!ryconnec:tions with tile higher centers. Besides the fl. bers that coordinate the parasympatttetSc nuclei. the fasciculus contllns other fiber systems that are not shown rn the diagram.

longlbJdlnal

fascial us

321

11.4 Autonomic Nervous System: Pain Condudion

A Piltnal'h!nmtsCIIIIductedfromtfll! vl!la!ra by till! symplltfletTc and P"I'IIIIYI'I'IPilthetk nervous systems

(
;a

a The

p;~ln-conduc:tlng

(nodceptlvl!) axons

fnlm the 11tscera COUI'$e In the splanchnic

nerves totnesympathetic gangli;l and reach the spinal nerve by W71Y qf tile white ramus communicans. The cell badlesoftheseneuronure locatl!d In the spinal ganglron. From the spinal nerve. the n~rons p;IU til rough the donal roots to the posterforhomoftile spinal cord. There they are relayed to establish a connection with tile asanding pain pattlway. J\ltematlvdy. a reflex arc may be est.1bllshed through lnterneurons (see 1). Note: unlike the efferent syrtem, the alli!r· ent nodceptive fibers of the sympathetic ;and par;osymp;athetic SYJtemS ;are not relil)'ed In tile perlpher;~l ganglra. b The cell bodies of tile paln-conduclfng pseudounipolar neurons in tne cronicrl para· sympattletlc system are located In the lnfe. rlor or superior ganglion of the Vigus nerYe (CN X). Those oftile $0CI1l/ p;~rasympatheuc $~ are loc;ated in the $aCral spinal ganglia of S2-S4. Thetr flben run p;~rallel to the efferent vagi! flbers and est.1bllsh a antral connection With the pain-processing systems.

52--_;;..---'-\

S3 -

---,- , - - -

5 4 - - - -___,_

322

Netii'OIJnatomy - - 1'f. AII!Ditomlc Nfi"'IIUS Symm

8 Rlllm!dpatn It Is believed thilt noclcepttlle ilfferent fibers

Esophagus (T4-T5)

from dermatDmes (somatic p.ain) and internal organs (vls«ral p.aln) terminate on the s;rme relay neurons In the postufor hom of the spinal cord. The convergence or somiltlc ;md visceral affi!rent fibers (see b) confuses therelationship ~ the peralved ~rid ~ctu~l sites of pain. a phenomenor1 known as re{l!m!d pain. The pa1r1 Is typleo~lly perceiVed ilt the sgmiltic site. ;~s som~tic pain is weU·Iaeo~lized ~lie ~saral pair~ Is not. Pain Impulses from a partiCIJiar Internal a~an 01re conslmntly proJected to the s;rme well.(feftned skin are;a (a); the p.attem of pain projection is wry helpful in determining the affected organ.

l..a'1jelntes'l_,~ --i'--,__,..,...,-~

{T11-l1)

,.,_ "'------

BI;wlder --+-H---+4~.,...-:~ {T11-l1)

•

Asa!ndlng pain pa!tlw;t;

Spln.11gangllon

- - S)mp;11t>e1k ganglion

Dlmlatome (Tl-14)

323

11.5

Enteric Nervous System

I.On!IIIUdrwl

--:-----..=~

mu!delqer

.f-I~H1--

lnti!ITtoll s.bmUCDSal (Melane!"s) ple.;a

HJ::.j~,._;!--

IIIUK!larlqer

dmuQ)M

A Entl!rk ftl!f'VOIII syltl!m rn the tl'llllll'ntettfne The enteric nervous system is the intrinsic nervous ~m of tfle bowel. consisting of small groups of neurons tilatform lnterconnKtEd. mlcroscople<~lly 11fslble gar~glla In !he w.~ll of the digestive tube. ItS two main divisions are the myt!lltl!fic(Auerbach) pJe;ws (located between the lon· gltudlnal ~nd clrtUiar musde fibers) and the Sllbmucosal pJaus (located In the submucosa), which Is subdMcled Into an emrnol (Schabadasch) and tnfl!mal (MeiS;Sner) submuco.sal p/t!XIlstS. (Detalls or1 the ftne lamina-

t1on of the enterfc nervous system e<~n be found In textbooks of histology.) These networks of neurons are the found;Jtion for autonomic neflex patftwiy5. In prfrltlple they can function witt! out extemallnr~UW­ tlon, but their actiYII:y Is Intensely modulated by the sympathetic arid parasympathetic nervous systl!ms. Act'Mtles Influenced by the entl!rlc ne1110us system ir~tlude entl!ric motility, secretion inw the digestive tube. and locallrrtest!nal blood flow.

l'myniptk: dlollnqk tl!IO
NCNAI!bef

(Inhibitory)

• I Modulltlon oflntatlnlllnnavltlon by the •utononic ncrw• system

Although the parasympathetic ntfVOUS system (•nest arid dl~t") generally promotes the activities of the diges!M!tube (secretion, motility), It may also produce lr1hlbltory effects. • Excitatory presynaptic: cholinergic par<Jsympathetic fibers b!rmin;ate

on excitatory cholinergic neurons that promote Intestinal motility (mixing of the bowel contl!nts to fadlrtate absorption). b All inhibitrlry parasympathetic fiber synapses with an inhibitDry gan· gllon cell that uses non cholinergic, nonadrenerglc (NCNA) tr.lnsmtt· ters. These NCNA transmll:ten are usually neurapeptldes that lr1hlblt Intestinal motility. c Sympathetic ftbers are not abc.mdant In the musaJiar layers af the bowel wall. Postsynaptic adrenergic fi~ inhibit the motor ;and se· aetory neurofiSin the plexuses.

324

Tht' dlnkallmportance of aUW!lomk bowel Innervation Is lllustr.lted below: • During shock, the vessds In tht' bowel are constricted and the lntesUnal mucosa Is accordingly deprived of Ol(}'!len. This results In dlsrupUon of the epithelial b.'lrrler, vmlch may then be penetrated by microorganisms from the bowel lumen. This ~an important mechanism contributlr~g to multisystem failure In shock. • Thene may be a cessation of fnteslfnal motility (atonic bowel) aftler intestinal operations involvifl!l surgical manipulation of the digestive tube.

• Medications (espedillly opiates) may suppress the motility ofthe entectc nervous system, causing constipation.

Netii'OIJnatomy - - 1'f. AII!Ditomlc Nfi"'IIUS Symm

Postsynaptic:

Nar-

symp;lthetfcflber

eplneph~ne

\

C

functSon;~l tntl!radfons of1M symp;dflettc ;md p;1rasympnhetk

Ml'¥0111 tyltil!n'ls at tile target organ The transmitters of the symp~thetic ~nd p;arasympathetic ntNIIU$ systems (norq~lnephrlne and ac:etylchollne. respectively) act upon

both the t1rget organ ind the (p;~ra)sympathetlc nerve endings at the synapse. Noradrenerglc receptors on the t1rget tissue (til. shown in blue) ~nd nentl! endings them~ves (a2, shown in pink) modul~tt' t1rget cell responses on two levels: norepinephrine binding to the P1re· ceptor directly promotes a aUular response In heart tiS;Sue,. while simi· Jar binding to the Q2 n!ceptors on the postsynaptic nerwendir~gs allows for regulation of subsequent neurotransmittEr release. through posltllle and negative ~back loops. The musCirfnerglc recq:rtors (m. shown lrl green} mediate a similar process upon binding of acetylcholine. The neurotrinsmltters of the autonomic nervous system Cirl therefore self· ;and cross·regul;att' in ;a multifaceted control mech;anism.

D Sympnhetk elfKts on ilrb!rfes An lmport1ntfunctfon of!he sympathetic nervous systl!m Is to regulate

the caliber of the ;arteriales (blood Pri!SSUre regulation). When symp;tthetlcftben release norepinephrine lnta the media ofthe arterioles, the a.l receptor medlat:e.s contraction of !he vascular smoolh muscle, ind the blood pn!tiure rises. Meanwhile, epinephrine from the blood acts on the P2 receptors In the sarcolemmil of the same YioSCIJiar smooth musde cells, lnduclr~g vasodilation ind a correspondlr~g drop In blood pressure. Noll!: Parasymp.rthetlctlben do not termlrl.rtl! on blood vessels.

Epineplrile (nhbltorvl

·~~~-t!al~i--~~ir--~~~ Smooth

.....,l) :..L...#-- -

mulde

t.'klcota gand

E Autonomic Tnnerwtlon of the tnlcftH ilndbrondll l'flrasympothettc stimulation of the lOCi! ganglia promcte.ssecmion by the brDnchial glands and nanrowlng of the branchial paswgu. For !his rei son, the prep;aratlons for bronchoscopy In dude the admlrllstratlon of a dnug (atropine) which blocks parasymp;athetic innervation, ensuring thit mucous secretions will not obscure !he branchial mucosa. A similar reduction In bronchial secret!OM tin be achieved through ~Jtimul
Dltnlon

325

Neuroai'H1tomy - - 12. Functional S}tmms

12.1

Sensory System, Overview

Nucleus!J'l~C~Js Nucleuse\1~

UAOlllsdOus plqJIIOCI!ptlon I'GIItlonsense, consdousproprfamptlol\

lllbredon, 11lUch

l'lln. tanper•ture

A Slmpltllllld dl;~gr..m ofthe Hflsory p;dtlw;ays of tile spln~l all'd stimuli generm Impulses 111 wrrous receptors In tile pe!'fphery of the

bel ely (see C. p. 179) which aretr~nsmitted to the cerebrum ~Ad arebel· lum along ttle sensory (afferent) pilthw.sys or tracts shown here (see 8 for detills). While mort oftile sensory qualities listed In I ire lni:IJI!ively dear (e.g. pain ind tlemperai:IJre sensation), the concept of propr'loa!p· lion is more difficult m COIM!!)' ~nd W111 be 9plairled in more detail. Pro· prio«ptlon Is con tooted with ttle position of the limbs In space (• posl· tlon sense). The types of Information lnvohleclln proprioception are complex: position sense (the posltlorl of the limbs In relation toor~e another) is distinguished fram motion sense (speed and direction of joint move· rr~ents) and force sense (the muKUiarforce iS50d.ated <Mth joint move· rr~ents). Accordlr~gly, the receptors for proprioception (proprlocep· 1Dr'S) consist milnly of muscle ind !lendon splrldles ind )oint receptors

326

(seep.328). We <~lso distinguish betweer1 consdous ;md uncoriSClocls proprfocepUon.lnfonmiltlorl on consdout prapltoa!pt'lon trlM!Is In the po.sterior funiwlus of the spinal cord (fasciculus gracilis ~Ad fasciwlus cune<~I:IJs) ind Is relayed through Its nude! (nucleus gr.rcllls and nudeus cuneii:IJs) mthe 11Jalamus. From there It Is conveyed to the ser!SOIYCOf· h!x (postcentral gyrus). where U!e lnformaUon presumably rises to consciousne.ss ("I kllow that my left hand is making~ fist. even ttlcmgh my eyes are dosed"). I.Mcollldollf propr!oCIIPtJon, which en<~bles us m ride" blcyde and dlmb stairs without thinking ibout lt.ls conveyed by the splnocerebellirtracts to the Cl!fl!bfJir.tm, wttere It remains at the unconscious lew!. Sensory information fi-Dm the he-ad is mediated by the trlgemln<~l nerve and Is not depleted here (seep. 330).

NeuroaiiGtomy - - 12. Functional Systems

B Synopsis of sensory pathways The various stimuli generate Impulses In different receptors which are transmitted In peripheral nerves to the spinal cord. The perikarya of the first afferent neuron (to which the receptors are connected) for all pathways are located in the spinal ganglion. The axons from the ganglion

pass along various tracts in the spinal cord to the second neuron. its axons either pass directly to the cerebellum or are relayed by a third neuron to the cerebrum.

Anterior spinothalamic tract

• Crude touch

• Hair foliicles • Various skin receptors

The perikaryon of the second neuron is located In the posterior horn and may be up ID 15 segments above or 2 segments below the entry of the first neuron. Its ~s cross in the ~nterlor commissure (see p. 274)

The axons of the second neuron (spinal lemniscus) terminate in thewntral posterolateral nucleus of the thalamus (see D, p. 219). There they synapse oniD the third neuron, whose ~s project ID the postcentral gyrus

Lateral spinothalamic tract

• Pain and temperature

• Most!yfree nerve endings

The perikaryon of the second neuron Is In the substantia gelatinosa.lts axon crosses at the same level In the anterior commissure (seep. 274)

The ~s of the second neuron (spinal lemniscus) terminate in the ventral posterolateral nucleus of the thalamus. Then!theysyn~pse onlxl the third neuron, whose axons project to the post· centr~l gyrus

Fasciculus

• Flnetouch

gr~dlis

• Conscious

• Vater-Pacini corpuscles • Musde;ond tendon receptors

The axons of the first neuron ~ss ID the nucleus gracilis in the lower medulla oblongata (second neuron) (seep. 276 and B, p. 233)

The axons of the second neuron cross In the br~instem and trawrse the medial lemniscus (seeB,p. 233)1Dtheventral posterolateral nucleus of the tllalamus. There they synapse ontcthethird neuron, whose axons project to the postcentral gyrus

•

The ~s of the first neuron piss lxlthe nudeus cuneatus in the lower medulla oblongata (second neuron) (seep. 276 and B, p. 233)

The axons of the second neuron cross in the brainstem and traverse the medial lemniscus (see B, p.233) ID the ventral posterolateral nucleus of the thalamus. There they synapse onlxl the third neuron, whose ~n s project to the postcentral gyrus

proprioception of lo.m"limb

F~iculus

ameatus

• Finelxluch • Consdous proprioception of upper limb

~ter-P~cini

corpuscles • Muscleand tendon receptors

Spino<erebellar tram Anterior spinocerebellar tract (of Gowers)

• Unconscious crossed

Posterior spinocerebellar tr01ct (of Flechsig)

• Unconscious uncrossed extero~nd proprioception ID the cerebeiium

~nduncrossed

extero- and proprioception to the cerebellum

• • • •

Musde spindles Tendon receptors joint receplxlrs Skin receptors

The second neuron is located In the dorsi I column in the central ~rt of the gray matter. The axons of the second neuron nun directly lxlthe cerebellum, both crossed and uncrossed, without synapsing with a third neuron (see p. 278)

The axons of the second neuron ~through the superior cerebellar peduncle ID the wrmi;on ~rt of the spinocerebellum (no third neuron) (see also p.243)

• • • •

Musde spindles Tendon receptors joint receplxlrs Skin receptors

The second neuron Is located in the thoracic nucleus (Ciarile column, stlllng nudeus) in the gray matter at the base of the posterior horn. The axons of the second neuron run directly to the arebellum without crossing (see p.278)

The axons of the second neuron ~through the Inferior cere· bellar peduncle ID the verml~n p;ort of the spinocerebellum (no third neuron) (see ~lso p. 243)

327

NeurDGnatomy - - 12. FunctlontJI Systems

12.2

Sensory System: Stimulus Processing Hair-follicle

receptor

Tactile

Heat receptor, nociceptor

disk

Cold receptor, nociceptor

Axon-Merkel cell complex

Epldennis {

Dennis

Subcutaneous {

tissue llal,..be.lrfng sldn

Free neNe

llalotesssldn

ending

Alpha motor neuron

~~-7---

lntrafusal mwclefib..,.

b

A Receptors af th• somatosensory sysb!m a Skin receptors: Various types of stimuli generate impulses in different receptors in the periphery of the body (illustrated here in sections through hair-beanng and hairless skin). These impulses are transmitted through peripheral nerves to the spinal cord, from which they are relayed and carried by specific tracts to the sensory cortex (see previous unit). Sensory qualities cannot always be uniquely assigned to specific receptors. The figure does not Indicate the prevalence of the different receptor types. Noclceptors (= pain receptors), like heat and

B Receptive Held sizes of cortical moduii!S In the upper limb afa primate Sensory information is processed in cortical "modules• (see C, p. 201 ). This drawing shows the size of the receptive fields supplied by modules. In areas where high resolution of sensory Information Is not required (e.g., the forearm), one module supplies a large receptive field. In areas that require finer tactile sensation (e.g., the fingers), one module SUJ>plies a much smaller receptive field. The size of these fields determines the overall proportions of the sensory homunculus (see C). Because one sldn area may be Innervated by several neurons, many of the receptive fields overlap. Information Is transmlted from the receptive field to the cortex by a chain of neurons and their axons. These neurons and axons are located at specific sites In the CNS (topographical principle).

328

cold receptors, consist of free nerve endings. Nociceptors make up approximately 50 t of all receptors. b Joint n~ceptors: Proprioception encompasses position sense, motion sense, and force sense. Proprioceptors include muscle spindles, tendon sensors, and joint sensors (not shown).

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

c Amlngement ofsensory p;dflwq.s rn the a!Hbl\lm Anterior view of the right postcentr~l gyrus. The perllc.uya of the thllll neurons of the sensory pathways are lo~ in the thalamus. Their axonsprojecttothepostcenlralgyrus.wheretheprlmarysomat»sensory cortex Is loa ted. The postcentral gyrus has a somiltotoplc organlz.rtlon, me~~ning ~t each body region is n!presented in " p<~rticular cortical area. The body regions In the cortex are n~t represented In p~~rtfon to their actual size. but tn proportion to the density of their sensory Innervation. The fingers and heild have abundant sensory reaptors, and so their mrtical n!presentnion is mrrespondingly la~e (seeB). Conversely, the len derue sensory lnnerv;atlon of the buttacle and legs results In smaller areas of representation. Based on these nrylng numbers of peripheral receptors, we can construct a •sensory homunculus• whose parU correspond to the cortical aneas concerned with their Pe<'ceptfon. Noll!: The head of the homunculus Is upright while the tnunk Is upside down. The axons of the Mnsory ne\lrOrl$ aKC!l'lding ftom the thalamus travel side by side wttfl the axons forming the pyramidal ttict(red) In the dorsal p<~rt of the Internal capsule. Because of this arrangement. a large cerebr~l hemonbage Involving the lntemal capsule produces sensory as well as motJjr cleficiU (5ft1Cell et al.).

t.mulsplno!Niamlctract

I

p~~--~~;-~~~ ~

s

sen so~

c

!?

OlrtEX

i!

Z l----......

• Superficial !H!nsatlon

Pl'l'SI\Irest~mlus

E Adtlltty ofcortlt.tl ull columns rn the prtmary b

""""~---- A'OprloC
D Prfm1ry tornltuA:I'IIIOry a~rtu: ll!d p~rtc:t.l-tltlon a~rtu: a l.clt lateril view. The Brodmann areas ue numbered In the sectional 11tew (b). The comnlateril body half Is represented In the primary somat:Dsensory cortex (except the perior~l region, which is n!Pfl!sentzd bllarerally: speech). This area of the cortex Is concerned <Mth somiltO· sensory perception. The p<~rtetil assacliltfon cortexrecdves Information ftom both sides of the body. Thus. the processing of stfmul! becomes irKreasiri!Jiy complex in these cortical arus.

~toryCIDita.

a Amplitude of the neuronal response In the primary somat»sensory cortex to a pe!1phml pressure stfmulus. The Intensity or the stimulus Is shown in b. The d-.agrams illustrate the principle of sensory information processing In the cortex. Whmapprwdmatdy100 Intensity detectors In the fingertip are stimulated by pressure. appradmatdy 10,000 neurons tn the corresponding cell column In the primary somatosensory cortex (see columnar organimion of the cortv. p. 201) fl!.IP~d to the stimulus. Because the Intensity ofthe peripheral pressure stimulus Is moudmal at the center ind fides toward the edges, It Is processed In the cortex ~ccollllngly. cartkal processing amplllles the contrast between the gruter and lesser stimulus int!!ns'oties, resulting in a sharper peak (a). While the stimulated a~ on the fingertip measures appmxlmately 100 mm2, the Information Is processed In only a 1-mml irei of the primary somatosensory cortex.

329

NeurDGnatomy - - 12. FunctlontJI Systems

12.3

Sensory System: Lesions

A Sites of occurrence of lesions In the sensory patllways (after B~hr and Frotscher) The central portions of the sensory pathways may be damaged at various sites from the spinal root to the somatosensory cortex as a result of trauma, tumor mass effect, hemorrhage, or infarction. The signs and symptoms are helpful in determining the location of the lesion. This unit deals strictly with lesions in conscious pathways.The innervation of the trunk and limbs is mediated by the spinal nerves. The innervation of the head is mediated by the trigeminal nerve, which has its own nuclei (see below). Cortical or subcortical lesion (1, 2): A lesion at this level is manifested by paresthesia (tingling) and numbness in the corresponding regions of the trunk and limbs on theopposireside of the body. The symptoms may be most pronounced distally because of the large receptive fields on the fingers and the relatively small receptive fields on the trunk (see previous unit). The motor and sensory cortex are closely interlinked because fibers in the sensory tracts from the thalamus also terminate in the motor cortex. and because the cortical areas are adjacent (pre- and postcentral gyrus). SubtiNIIamlc lesion (3): All sensation is abolished in the contmlaterol half of the body (thalamus - "gateway to consciousness"). A partial lesion that spares the pain and temperature pathways (4) is characterized by hypesthesia (decreased tactile sensation) on the controla!Erul face and body. Pain and temperature sensation are unaffected. Lesion of the trigeminal lemniscus and lateral splnotiNIIamlc tract (5): Damage to these pathways in the brainstem causes a loss of pain and temperature sensation in the contrala!J!rolhalfoftheface and body. Other sensory qualities are unaffected. Lesion of tile medial lemniscus and anterior spinothalamic tract (fi): All sensory qualities on the opposit!? side of the body are abolished except for pain and temperature. The medial lemniscus transmits the axons of the second neurons of the anterior spinothalamic tract and both tracts ofthe posterior funiculus.

330

Lesion of the trigeminal nucleus. spinal tract of the trigeminal nerve, and lateral splnotiNIIamlc tract (7): Pain and temperature sensation are abolished on the ipsilateral side of the face (uncrossed axons of the first neuron in the trigeminal ganglion) and on the contmla!J!rol side of the body (axons of the crossed second neuron in the lateral spinothalamic tract). Lesion of tile p01terlorfunlwl1 (8): This lesion causes an ipsilateral loss of position sense, vibration sense, and two-point discrimination. Because coordinated motor function relies on sensory input that operates in a feedback loop, the lack of sensory input leads to ipsilateral sensory ataxia. Posterior hom lesion (9): Acircumscribed lesion involving one or a few segments causes an ipsilateral loss of pain and temperature sensation in the affected segment(s), because pain and temperature sensation are relayed to the second neuron within the posterior horn. Other sensory qualities including crude touch are transmitted in the posterior funicu· Ius and relayed in the dorsal column nuclei; hence they are unaffected. The effects of a posterior horn lesion are called a "dissociated sensory deficit." Dorsal root lesion (10): This lesion causes ipsilateral, radicular sensory disturbances that may range from pain in the corresponding derma· tome to a complete loss of sensation. Concomitant involvement of the ventral root leads to segmental weakness. This clinical situation may be caused by a herniated intervertebral disk (seep. 345). lesions of unconscious cerebellar tracts that lead to sensorimotor deficits are not considered here. The volume on General Anatomy and Musrulosla!/etal S_vsWn may be consulted for information on peripheral sensory nerve lesions.

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

KM+-- - - - - - - - Sphallemnll:l:us

(~nterlot.,dlatml

lpir>Othalolmk ~Cl)

1----Tlfgemln.ll lemnlsclls

-H-- - - - Lat!el'liiSII(r!Otflllamlc~ct

- -+- - - : ----i TI"+-1'--- -.;....--

Print~l (pont!M) nude~ad trlgem'mi~WM

-+":"-'=-- - - Spl~lnudeusol trlgemilll nenoe

Lat!e!'lllsplr!O-

- --1

!----+- - Tr.u:tsol

posteriorlunlt\llus

thalilmlt ll'act

10

331

Neuroai'H1tomy - - 12. Functional S}tmms

12.4 Sensory System: Pain Condudion

I

~~

....

41

II

II

51dn

I

Plnplldc.

prusure

o.ppalll

fr

II

N..-..,.lldc pain

fr

ConneciM tlllue. musda. bana.Jalnll

NIIWI, IIIIWtllsUe

MusdeJPUm, heamdle

N
I ~

...

~

A Synllplll of p11n mDdallttK The International AJ$oclatlon for the StiJdy of Pain defines patn
Polt:2flcr ---~ ham

II

II

I

Vllmnll pain

41 Vllmnl

Bllary coliC. uiCI!f,

appendicitis

""-"' .....

nerves themselves. It rmy involvto nerves of the somatic <~nd/or auto· nomic neM~us system. The somatic p;~ln fibers described below travel with the spln.al or aanlal nerves, while thevlsceril p;~ln fibers travel with the autonomic nerves (seep. 322).

lSI~~~..,..--,--;..-

l'reenerYe

endings (noclaeptlart)

I Perfphcnl smM'II' plln condudlon (<~fter l.orke)

Somatic pain Impulses from the trunk <~nd limbs are conducted by myelln.ated M fibers (temperitUre, pain, poslUon) .md unmyellnmd c fibers (temperitUre, piin). The perikarya (all badies) for these affi!r. ent nerw flbers are locmd In the spinal ganglion (p~dounlpolar neu· rons). Thetr ax.ons terminate In the postafor hom of the spinal cord,

332

chiefly In the Rexed laminae 1. 11. and IV-VI. The noclceptors, ilffa'ent flbers ascend aftef syn<~pslng In the posterior hom (see C). Note: Mostsom.rtosensory piln fibers are myelinated, while the viscerosensory fibers are unmyelinated.

Neuruanatvmy -

12. FunctlonaiSysmns

-.......... Jr.'------ Glglni>Dcollullr nudftll ~,.·--~ --=---- Nuckus SpinomHI'I\aphallc

tr.a

I'll........... thal;mlc port

.._..

- ---!f,l/

I

~~IN!JIWol$

- - - Spii'IDI'eltlJar tract

splnothal;mlc

tnct

{

NeCIOJ)Inothol;mlc port

C A.cendlng p•ln P'thwly$ from tile t111nk•nd limbs The ~ns ofthe prtmary lfferent neurons for p;~ln senmlon In the trunk and limbs tennlnate on the projectfon neurons (shawn abave) located In the posterior hom of the spinal-cord gray matter. The lateral splnolhillilmlc tract Is subdfvfded Into a neo- lind pile05plnothalamlc part. The -ond neuron of the ~Gicrmic port of the p;~in ~ (red) terminates in the vmtril p05terolitenl nudeus of the thalamus. The third neuron projectsfrom thin! to the pr1mary somatosenSOI)'cortex(postantral VYrus) ofthebraln·. Thesecond neuron ofthepcrleosptnotholomlctrvct (blue) termlnat.s In the lntrilimlnu lind medial nudel of the thalamus, wh- third neurons then ptoject to a variety af brain regions. This pain pathw..y Is m~nly retponslble for the emotioNI component of pain. In addition to these p;~ln pithw¥ that end In the cor-

- - - Splnllcanl

tn, there are also pain pathways that end in wbcortkrl/ regiont-the

splnomesencephallc tract and .splnoretlculir tract. The secor~d neuron of the~ troct (green) terminates m:alnly In dle central gr..y matter. which surrounds the ~queduct. Other axons terminate In the cuneiform nucleus or interior pretecti Inucleus. The second neuron of the spin~111Jct(orange) ends in the reticular formation, repre· sented here by the nudeus n1 phes nnagnus and the glgantocellular nudeus. Retlculothalamlc fibers transmit the piln Impulses onw.ilrd to the medial thalamus. hypothalamus, and limbic system.

m

Neuroai'H1tomy - - 12. Functional S}tmms

12.5 Sensory System: Pain Pathways in the Head and the Central Analgesic System

""'""i----- Tlwl~mus. Yen11'<11~ medtll ntldt\1$

- - Tr!Qemlnothllamlc tr.lct

Ollhth;Jimlt . _ (CN Vd

Spi'n;ll nLideus af { ttlgemln~lne'lle

A htn p;lthwilys In tile hNd (after lorlce) Tbe p.aln ftben In the head ac:comp.anythe prtnclpal dMslons of the trl· geminal neNe (CN V 1-V3}. The perikarya of these primary affi!tent neu· rotu of the pain pathway are loc<Jted In the trigeminal 9'1ngllon. ThEir illiOIU tennlnate In the spln<~l nucleus ofthe tlfgemln<~l nel"'e. Nab! the sorn.iltotopk organiZation of this nuclear region: The penor.ill region (a) is cranial and the DCcipital regions (c) are a udal. Because of this arr<~ngement. central lesions lead to def!dts that .ilrt' distributed along the S!lldef lines (see D.p. 75).

334

The axons of tile second ne~mms cross the midline and travel In the trtgemlnaChal.ilmlc tr.ilcttothe ventral posteromedial nucleus and to the inlr.llaminarthalamicnuclei on the opposite side. where they terminate. The third (thalamic) n~ron of the p.aln pathway ends In tile prfrn.ilry somatosensory cortex. Only the p.aln flbers of the trigeminal nel"'e .ilrt' pictured In the dlillgram.ln the trtgemln.ill nel"'e Itself, tile othefsensory fibers run p;~rallel to the p.ain fibers bvt terminate in various trigeminal nuclei (seep. 74).

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

B ~ ofd!.e antnldeSO!I'Idlng

-lgetTcsyltl!m (after Lorlce) Besides !he ascending pathways tililt tallY pain sensation to the primary somatosensory corte., there ~re ~lso destl!nding pathways thathavelheabilltyto5Uppresspaln lmpcJisu. Thecenttal relilystatlonforthedescendlngan~lgeslc (paln-relrev!ng) system Is the central gr~ matter of the muencephalon. It is actiYo~ted by afferent lnpcJt from the hypothalotm~JS, the prefrontal cori2X, ;mel the ;unygelotlold bodies (p.art of the Umble system, not shcwn).ltalso reaiveul!i!rentinput from the spinal cord (~ep.333). The axons from the excitatory glutamlnerglc neurons (red) of the central gr~ matter terminate on serotonlnt!'gic neurons in the raphe nuclei and on nora~ renergk neurons In the locus ceruleus (both shewn In blue). The ax.ons from both types of neuron de.scend In the posterolaterlll funla; Ius. They tenninate directly or indirectly (via Inhibitory neur01u) on the analgesic projection naJrons (second afferent neuron of the pain p;athw..y), thereby Inhibiting the further conduction of pain impulses.

W "¥t- - - - Anteior

prett
~~~~----

!«us

an.feus

1.'7 - - - Posterdateral funlalus

"--ng ...d

conduc:llonofnoda!pllole Nodap!M Signal CIDI'Iductlon In the

I Pe~ralor

epld.nl neMeblock

t

t

psycho1hmpe\ltlc tKhnlques

net.rOS~I!IY

\ lnftamiNIIon, edsN, fomwllon

or pain mediators

t

lntl11~braln

signals In tile spinal CDid

Systemic« epidural opiateS, .stlmllatlon t!lenpy,

peripheral nerw

l'loclesmg or nodCEplllle signals

<=

-

Genml anesthesia.

C Plln pcm:ptfon 1nd thcnrpeutk Interventions

Pafpheral pain m..y be caused by local tissue Injury from a bee 5tlng, for example. The Information on this Injury Is transmitted by sewral ~liY sbtians to the primary somatosensory cortex, where the sigr~als are perceived as pain (translmd from simple encoded Impulses). Pain. then, Is a complex experiential phenomenon that Is processed ;mel relayed at wrtous levels In the nervous systi!m, and so there are multiple ll!vl!ls at which pain may be alleviated by ther~peulic measures (red arrows).

lmmoblhafol\ coding, analgesic mecllcaUcn, antt-nflamiNIIIOIYmed'catlon

335

12.6 Motor System, Overview

-

--nt

A Slmplllled~onflltlle ..-..nlul slnlclllralnwlwd In avalunt.aiY (,r.mlllelmotor syltem) (aftw lOin• ~nd Sllbern~gl) The first .s,tep In performing 1 voluntary II'IOII'ementis to plan the ~ent in tfle assaci~ tion cortll:x of the cerebrum (e.g., goal: 'I want to piCk up my colli!e cup"). lhe arebelbr hemisphl!res and bnal g1ng lia wori< in par11lel to program tfle mOYI!ment 1 nd Inform the p~ motor cortex ofltle result Df ltlis planning. The premDtor cortex passes the Information to the pr1mary motor cortex (M1), which reiiys the information ltlrough the pyrrunida/ lniCt tD the ilphi motor neuron (pyramJdol motDf qmm). The alpha mot:Dr neuron then lnltfates tfle proce.s,s whereby thl! skeleul musc:le transforms the program Into a specific voluntary II'IOII'ement. 5ensor1matDr functions supply lm poruntreedback during this process (How far has the mCM!ITient progressed1 How strong Is my grip on the cup handle7-di~rent from gripping ~n eggshell, forexample).Aithough some of ltle I.mer ligures portray the primary motor COI"tell u the starting point for a volunury mOYI!ment. this dl~gr~ m shows that many motor centers are iRYOivoed In the eJIIKutiOn of a voluntary mwemart (Including the~ mldol malrlr symrn, see c and D; cerebellum). fGr prilctic<JI Ruons, hDMftr, the dixuuion commonly begins at the pr1mary motorcormx

-~::----'--=-~~..,.....,..---- -

homlsphera

•

(M1).

-------------------;------------------------------.---------'------, ~ Scmnooenoary

B Carlkilll I I'MI wldlmator fwldlan:

lnbmlllan

lnltT.Ung • mowment Literal view of the left hemisphere. The Initiation of a voluntary movement (reaching fur a coffee cup) results from the interaction of Yllrlous cortla Iareas. The prlmoiymotor c:otta (M1, Brodnnann area 4) Is loated In ltle pre-

centnl gyrus (pecutlon of a mOYI!rnent). The rostrally idjilcart area 6 consists of the lateral premotor cortex and medial supplementary motor corWI Onltlatlon of a mOYI!ment). AssDclatlon fibers (seep.l76) establish close functional connections with .s,en.s,ory ilreu 1. 2. .;md 3 (postmntral gyrus wttfl prfmarysomltosensory cu.UX. 51) and with a~s 5 and 7 (= posterior parietal cortex), which ~ in auodatfve motor funcUon. These area.s, prc>vide the cortical representitlon gfsp;~ce.which Is lmportint In precision gqsplng mowments and eye movements.

Supplomonlllry

mo!DrCOI'ID Preantralgyrus

\

(prtmory mllllr - - - - - - - . \ cortn.Ml) . ~ I' Pn!mabr

cortn

-----c-.,.---

Centnil lOllall

I

f /

PostanlniiD'US

. / (p~lllllrysomatosensorymrtooc)

c

CDnnecflonl Clfdle mrta:Widlthe lasal glft!llll lnd cereellum: P"'tnmml111 mmpla...-mlnb

I

l'lllldum

The pyrimldll motln 'ystem (the prfmarymoIDr cortex 1nd the pyrimldi Itract 1rlslng from it) i5 apirted by the INS.JI ganglia and cerebel1urn In the pl1n nlng 1nd programming of camplex mCM!menl:s. While illfterent fibers af the motnr nuclei (g.-,) pR!Ject directly ID the biiSal ganglia (left) without syn;1 psing, the arebellum Is Indirectly controlled via pontine nuclei (rtght; seec;. p.2l3). The moan thalamLJS piVIIIdes a feedbick loop for both structures (seep.341). The effetl!!nt fibers of the biiSal nuclei and cerebellum are distributed to lowl!r structures lndudlng the spinal mrd. The lm porta nee af the baul g~ngl~ and cerebellum in voluntary lnCIV8Tients can be apprec:tited by noting die ~IS af lesionJ In these structures. While disuses of the biul ganglli Impair the lnltlatlan and I!XI!cutlon af m~ mlflts (e.g., in Parldnson's disease), ~bellir lesloru are ch1ncterlzed by unmordlnated writhing lllCNaTlents (e~ .• the reeling mowments of lnlbr~tlon. a used by a tempon ry txWc insult to thto ~bellum).

I

I

c..b,.lmrtlol

I

1 L1 1 1 I Thollmus

I

I

9

c...!MIIam

I

1

-1 71

I

1

Splnol CD'd

t

I

L__-... _-_ ...._-_ ___.I-LI_SIIolml_,.,_ldiDI_rnotDr_. _

_J

D Simplified lllodl dliiQnrm Ill die sellllllfmalortyltl!m In m-ment contra! Volu nblry movements require constint feecl-

back from the periphery (muscle .spindles, tA!ndon organs) in order 1:4 remain within the desired limits. Because die motor and sensory systenu are so dosely ln!z!Telited functionally, they o11re often described Jointly .n the sensorimotor system. The spinal cord, brainstem, cerebellum, and cenebnl cortex are die three control level' af the sensorimotor sy5tem. All lnformoiltlon from plflphery, cerebellum, and the bisal ganglia passe through the thai:! mus on Its MY to thto cerebral cortex. The din leal lm portance af tht- sensory SY'~ In movement Is lllustnted by the sensory 1tD11 that may oa:ur when sensory functian is lost (see D. p. 353). The oculomotor camponent of the sensorfm.otnr system. Is not shcMn.

337

12.7

Motor System: Pyramidal (Corticospinal) Tract

Nm~~i~~ Pylamldal

faao--..,....-'

A Caui'JII! Ill the ,nmld•l (mrUmspllnll) 1nct The pyr;~mida Itract consists of three fiber systems: corticospinal fibers, cortlconudear fibers, and cortlc:oretlcular fibers (the l~r ire not shown here; they pass to the glgantocell ular nudeus of the reticular fvnmtion in the brainstem and will not be diSCU$Sed further). These groups of fibers constltub! the descending motor pathways from the primary motor cortex. The corticospinal ftbers piSS to the motor anterior horn cells In the spinal cord, wh lie the cortlcon udear fibers piSS to the motor nuclei ofthe Cl'1 nlal nerves. COrtlcolpTn•l fllen: Only a SINII percentage of the i!XOns of the corticospinal fibers ortglnate from the large pyramidal neurons In lamina V of the precantral gyrus (the laminar structure Ill the motor cortex Is shown In D). Most of the iXIIIIS irlse from sm;lll pyramidal cells and other neurons In Ia mlnae V and VI. Other IXOOS ortglnite from ad)ilcent brain regians. All ofthtrn detand through the intl!!rnal capsule. Eighty percent ofthe fibers cross ~ ntldJIM It the level of the medulla oblongata (decuSSitfan of the pyramids) and descend In the spinal cord as the /crtmJI CDttitvtrpinQI (pyromidr;rl) trclrt. The IHIC106sed fibers descend In the coni iS the ontMo!' cortlco!plna/ (pyramidal) ttoct and aoss liter •thesegmental I-I. Mast of the amnstl!rmlnlll! an lntercalatl!d cells whose synapses end on motDr n~uvns.

338

}

trxt

Nob!: the biiSic patb!rn of sami!Otaplc orvanlzitlon described earlier at the spinal cord level is found at all level$ of the pyramidal tract. This ficllrtates IDCi!lrmlon of the lesion In the pyramidal tract. COrlkDnuclelr fibers: The motor nuclei and motor segments of the cranial nerves receiw their iiXDns from pyramidal cells in the facial region of the premotor corm. These cortlconudearflben terminate In the contralateral motor nuclei of cranial neiWS Ill-VII and IX-XII In the br.~lnstem (the fibers to other br.~lnrtem nude! are shown In C). Besides this contrillateral supply, illCDns also pus to several cranial nerve nude/ on the $;!me (ipsilateral) side, resulting In a bilatetal innervation pattern (not shown ha-e). lhls dual supply Is clinically lmpoltmt In lesions of the frontal brand! afthe fadal nerw, for eumple (seeD, p.. 79). Notes on the • pyramida I tract": Some authors interpret this tl!rm as i!pplylng sb1ctly to the porUon ofthe tract below the decussation Illthe pyramids, while other authors apply the term to the entire tract. Most publlcatlons,lndudln9 this •das. use "pyramidal trict" as • collectl¥e term for all of the ftber tracts desafbed here. Some authors derive the term not nvm the deWSo1ation of the pyr;om ids but from the giant pyramidal cells (IIetz cells) In the cerebral ortu (seeD and p. 211 ).

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

B

Som.ltatoplc~nofthetb!fetalmlllde

In the pn:ccntnl !jyruJ (motor homunc:UuJ)

Anterlor111ew. Regions In ~lch the muscles areverydenselylnnesvated {e.g., the hand) must be supplied by many neurons In the precentral gyrus. As. a result, they rt<juire a largerrepresentation area in the corta than regions supplied by fev.w n~rons (e.g., the trunk). This cortical representation Is analogous tD that In sensory lnnervatfon, where areas af varying size are also represented In the a:ortex (postcentral gyrus; compare with the - r y homunculus in C. p. 329). One cortical area Is devoted tD the trunk and limbs and another tD the head. The <~XDns for the he
&.....-----Nuclaof n!tlwllr

formrtfon Do13.111alumn nuclei

Multlfonn . ,(\II)

(pleomorphic aolls)

C V..rtetyofcortkillllferenttlbers

Antenor lllew. Be.sldes the corticospinal .mel cortlconuclear ftbers de· scribed a~ a variety of ax.ons descends from the cortex tD vari~:~us subcortical regions ;md lntD the spinal cord. The following subcortical regions also receive cortical efferent flbers: the COfliUS striatum. thala· mus, red nudeus, pontfnenudel, reticular formation, lnfertorollve, dar· sal a:olumn nudei (these nudear regions are described on p.342), and spinal cord. The supr<~splnal efferentflbers listed above consist partially of axon col laterals from pyramidal tract neurons and partially of separ.rte axams.

D Lilmln;r strudure of the motor cortex(= iln!i14ln the precentnl gyrus) The amns from giant pyramidal cells (Betz cells) in lamina Vaca~unt for only a small paant<~ge (<4%) of the axons that nn<~ke up the corticospinal tract. Small pyramidal cells and other neurons from laminae V .md VI contribute the rest. In .ill, however, only about 40:1 of the UDns afthe pyramidal tract originate in area4. The rem<~ining 60,; mmefram neurons In the supplement.lry motDrfiekls (seep. 336).

339

Neuroai'H1tomy - - 12. Functional S}tmms

12.8

Motor System: Motor Nuclei

Subtlllllamlc

nuc:ltus

Nuc:ltus - ----:----::lr-- -.....:.- -

aabus pal IIIlis,

lmral segrne.-

aca.mbu"

aabus pal IIIlis.

medal segment ~rt

part

Sub!tlntla nlg~

A Motllrnucle1

Coronal section. The bas.al ganglia .are subcortlc.al nudel of the telen· ceph~l~n th.ilt have a role in the pl;lnning ~nd encution of m011ements. They are the central relay st.iltlon of the extrapyr.amldal motor system and make up .illmo~t .ill the centr.ill gray miltter of the cerebrum. The Dilly other antral gray-matter stJucture is the thalamus, wflich is pri· marily sensory (•gatn'ay to coruclousnns•) .ilnd Is lnwlved only sec· ond.ilr11y. throcJgh feedbackmechilnlsms.ln motor sequences. The three largest motor nuclei are: • caudare nucleu~. • Put.ilmen, and • Glo!xa P.illlidus (developmC!Ilt.illly. part of the diencephalon). These three nuclei are somelfmes known byv.arylng colleclfve deslgn.a-

tfons:

340

• The knt/foml nctelfus Is formed by the putamC!Il, globus pallldus. and lnterYC!Illng ftbef tr.ilcts. • TheOlJJIClSstriotum consiro-ofthe put.ilmen. caudate nudeus. and intef'Venlng streaks c4 gray matter. In iddltlon to these three nuclei. there are other nuclei!Nt .ilre considered functional components of the motor sysb!m (also shown hen!). 11'1 a strictly anatomlc.al sense. ot'lly the U!lencephalk structures listed above are constituents of the basal ganglia. Sometextboob mist;~kenly Include the subtholamk nudws of the diencephalon (see p. 224) ind the Sllbstonrta nigra of the mesencephalon (seep. 228) among the basal ganglia Ilea use of their close functional 1'1!1ationshlp to nuclei. Rmctioml disturbances of the basal nuclei are cba~<~Cterized by mciiiC!IT1ent dlsonders (e.g•• Pirldnson•s disease).

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

Supplementay motcrcortex

-

Premotcr

------1'"""=--...;_-

Conlal elferEntflben tobl\lln:s«m and spbollcord

Cemromedan

----.----<;iii"""'~"

nudtill

s 9 1IT-:l- - - - Globus palldus. 12ar.!l segment

Vemr;allatl!r.ll --~~nudtol

'--:;,L-:, L - : f - - - - - Globuspalldus. medial segment

Ctlmp.;ld

part

B

now ofTnfom'lltfon between motor coltl'c.tl•reBnd balllg~ngllla: motDr IDDP

The biiSal ganglia are contooled with the ccmtrolled. purposeful exe· OJtlon of ffne YDiunt;uy mCMments (e.g•• picking up an egg without breaking It). They Integrate lnforma!Son from the cortex and subcortical regiom, which tneyprocess in par~llel ~nd then return to mawr cortical areas 1/la thetnalamus (feedback). Neurons from tne prernotor, primary mawr. supplemei1Ury motor, and somatosensory cortex and from ttle p.arfetallobe send their .axons tottle putamen (seep. 209).1n1Uallythere is a direct (yellow} and indirect (green) patnway for relaying the infl:lr· matlon out ofthe puUmen. Both patilways ultlrnatelyleadttltnemotor cortex by Will'/ of the thalamus. In the direct pathway (yellow), the neurons of ttle putamen pro}ect to the medial globus pallrdus and to ttle reticular part of the substi!nlia nigra. Both nLJC!ei then l'l!tum feedback signab to tne mawr thalamus, which projects back ttl motor areas of the cortex. The fndlrrct patflway (green) leads from the putamen

R.etklllar part

thnough the liltll!r.al globus pallldus .mel subthalamic nudeus back to the medial globLIS pallidus, which then projects to the thalamus. An alternate Indirect route leads from the subtnalamlc nudew ttl tne retlcular part of the subst.antla nigra. 'Which In tum profects ttl the thalamus. When Inhibitory dopamlnerglc neurons In the compact part of the substantia nigr;~ cease to function, the indirect pa~ is suppressed .and the direct pa'dlway Is no longer faclllt.ated. Both effects lead ttl the Increased lnhlblt:fon of thalamocortical neurons, result:fng In decreased movements (• ~ dlscu'der, e.g., In Parkinson's d!se
341

12.9 Motor System: Extrapyramidal Motor System and Lesions

~~~~-------~1

~nttlelrKt

Oa:lpllD........,. ----:-------

czphdctrad:

Put:JIN!I'I and - - - -

globus ~llldus

~lcortla>-

'Pinaltract

- - - --++--1

~lwstbulo>. ------,#----14~

spiNIITKt

_ _ _ _ _ _ blla.llooplnol

tract

ftber(1a)

r-~~~-~--~--lmemwmn

Colglfbef(1b)

-.......!'--------=:=.....-- Alpha motor ntuiCII ca1Fber

yFlber

A De~eendln1 tram lilt the extnpynmld1l matar sptem The neurons of origin of the desanding tr.lc:ts of the exlr.'l!¥ilmidal motor system • 1rtse from 1 hellerogeneous group of nudeIthat lndudes the basal ganglia(pubmll't, globus pallldus, and cauclab! mx:leus), the red nucleus. the substilntt1 nlgn, 1nd mm mutur cortiCII areas (e.g., area6). The following desa111dlng trlc:ts arlt put of thlt extraP'J'ramldal motDr sysb!m:

• Ru bro:spinal t"ct Ollvosplnal met Vltstlbu losplnlll tract Rettculosplnal met Tectospinal trlct

These long desandtng tnc:ts Um11na on lnterneurons whkll th111 farm synapJQ vnto alphl and gamma motor ne\Jnii!S. which they con-

342

!:---+ ---:------ '!Kto6pll\lltratt ~~...,_

Anr.~llllpnl --~'/

• • • •

1-- - - - - - tplnalll'oltt Antlrtorcortla>-

trol. Besides these long d~cendlng momr tr1cts, the motDr neurons additionally rta'ive S$1sory input (blue). All impulses in these pathwilys are Integrated by the at phi motor neuron and modulatE lb ldlvlty, thereby affecting muscularcontracUans. Th1 functional Integrityoftile alpha motor neuron Is tested cllnlc111y by reflex testing. • TheWml "extr.lpyramidal motln system• has bee! critidzed ~ause Its functlonil and inatl:lmiCII components 1re so closely llnlced to the pyramidal motor system that the dlstlncuon seems arbitrary In an anitomle~l sense-p~rticular1y since the sysllem does not lndude cerebellar tnc:ts that ill'l also lnvolwd In the control of motor function.

Neuruanatvmy -

12. FunctlonaiSysmns

Leg

~ Tru'* -

--r- - Arm

Pynmlclll }

t iXI

•

~)

Pyromldll tract

I Lesions afthe mnlnll rnatDr ..,._.and thelrefhds

ducent nucleus may ause lpslllbnl d1m1ge to the trtgemlnal nudeus

LefTon'*' the c:or11tll (1): paralysis of the musdes inn~ by the

(not $hown).

damilged cortlal iln!l . Beause tbe face and hind iln! represented by partlculilr1y l1rge iii'HS In the motDr cortft (see I, p. 339), par.1lysls often affects priiTiirily thun11 and face ("brachiofacial" paralysis). The parillysls lrm rtibly ilffects the side opposltl! the lesion (decussation of the ~mlds) and Is flaccid and partbl (pareslsJ r.ather than compll!!b! beause the extrapynmldil fibers are not daiTiiged. If the emapyramldal fibers were also damaged, the result would be complete spastic pcrttJI)$is (see below). Lesion at the lew! of the lnlilmll capsule (l): This leads to chronic. contralateral, spastic hemiplegia (• complete pariiilysls) beause the lesion affecb both the pynmidil tnlc:t ;md tbe extr<~pyramidal motor pathways, • whldl mbe: with pyramldill tract flbers In front of the lntema I capsule. Strola! is a frequent c.aute of lesions at this level. &.Ton at the lmll of die wl'lllnl pecbxl• (cnll'll c..bd) (3): contrillaterillspastk hemlpaAISis. LefTon .t the len! of the~"'"' (4): contralateral hemiparais or bii;tm~l p;~resls, depending on the saze of tbe lesion. Because the fibers of the pyrilmldal tract ocaJPYI larger cross~edlonill il-ln the ponsthm In the Internal c!ipsule, nllt illl of tbe flben - daiTiiged In milny cases. For ewnple, the ftbers for the fildill nerw ilnd hypogiOSYI nerw UIUOIIIy un~tcd bec!iuse of their dorul loation. Dilmage to the . .

Lesion It the left! of the ,nmld (5~ Fludd contnl~l p;~resls occurs beause the nben of the tlltnpyrilmldill motor pathways (e.g., the rubrospinal and tectospinal tract) are more dorsal than the pyra· mldill tract fibers and are therefore unaffected by iln Isolated lesion of the pyramid. Lellon It UI•INII of tile spln•l ani (1. 7): A le~lon at the level of the cervical c:ord (6) leads to lpslllbnl sputlc hemiplegia because the fibers of the pyramidal and e.dnlpyr•midal •ymm •re closely interwoven at this level and hwe already aoued to the opposite side. A lesion at the levi!Iofthe thoradc coni (7)1eads tD spastic pariiilysls afthe Ipsilateral leg. l.ellon Ill: the le'llll!l Dfthe pertph-IMnl'l (1): This lesion dilmages the axon ofthealphol motor n..,ron, resulting in fbcdd paralysil. • Thus, sp~stlc pir<~lysls Is ilctually ilslgn of lld:r.~pyr.~mldal motor dilma§le. ThiJ fact wn unknown when pyramidal tract lesians first described, however, ilnd ltw;a m umed thilt 1 pyrvmldal tract lab! led to spastic p;~ralysls. Because this fact IYs few pradlc.al Implications, spasticity Is still desalbed In some textboola as the d u:slc Jlgn of il pyramldill net lesion. It ~ld be betUr simply tD regard spastic pillalysis a a fon11 <:1 a>ntr.JI pi~lysiJ.

343

12.10 Radicular Lesions: Sensory Deficits Dur.~millr

C4 T2

b spl~l

gongllon

cs

_)

-----

T4

I

T3

H

T6 T7

\

T4 T5

n T7 Tl

Til

TID

• A Cilludiillnd vfthelplnal cord 11111cilu• -.ullllllnthewriH1'8IoMI Mlclsilglttal section viewed fnlm the left side. The splnil cord ends appr'OIIdmiltely it the L1 level, and the neural tissue in the vertebral canal be.low that ll:'t'd consists only of ventral n dorsal roots (see abo p. 269). The ventral moblr root and dorwl sensory root unite in the fntel"'mtddraf foramen ID form the spinal nen~~t. The roots enter and t!lnerge frDm the spinal dural sac through ' - sep~rate openIngs {b). This Is the anii!Dmlaf bub for the ~d that set'ISGry ddlcits (p~in, lou of sens~ tlon) and motor deficits (muscular weakness ranging to p~rillysls) m.l)' develop separately In patients with nft"le root compression (see E).

B PnajKtlon vf l'lllllcullr fnn.wtlon 111111 tha Arn: d1111111tom• After the dorsal1nd -m I roots unite tn fonn the spln.il nerve (see A), their nerve fibers Qre distllbutl!d to their respective territDfoes. The Q reg of skin that Is lnnervmd by the flben of1 single donal root Is e~lled a dMnatumr.lfthe dorsil root Is dilmilged (e.g., by pressure from 11 herniated inle~tbril disk), sensation may be <~lte~ in the areil supplied bythe root. An result, the lewIofthe d<~m~~ged nerve root an beldentlfted by notlng the dsmatome llffected by the 5erJSary loss. Beause the C1 segment c:Qnt-ilns only mcltxlr fibers. there Is no C1 dsmatoJme.

344

Tll

TI:Z ll

Tl

L4

cs

Tt

TID Til TI:Z ll ll

u

l4 LS

Sl Sl SJ

S4 L2

cs

Tl

Nf!uiOGDGtomy - - 12. f'undiomltiSymms

Sp'hal ner.oe 'h

Sensol)' doni.JI root

ltl~l'nti!M!rtl!bral

Petlpheral

MD!mum area npplled by a

foramen

ner.oe

cut;neousneM

Dorstl111mus

01/eriapplng temtorles

oii\No cut.Jneous netW:S

C LIK.Itlon oh nldlcullr lesion Aradicular lesion Is loc.rted on the venlral motor root or dors.ill sensory root between 1ts slte of emergence from the spinal cord and the union of boCh roots tb form a peripheral nerve. Accordingly, a lesion d the ventral root leads to motor deficits (see p. 346) while a donal root le· s1on leads to sensory disturbances In ttte corresponding dermatome. The dermiltOmes on the limbs are shifted because of mlgr.ttory proasses during embryonic development, but the dermiltOmes on the trunk A!t
<-...':">--- ---=--=-- - - - Ant2flor cutanecw;

br.lndlK

D lbdlcuillrlnnerwtlonoftfletrunk The scgment.11 arr.-angement of the musculature Is preserYed In the trunk. and so ttte ttunk ret.11ns a segmental (radicular) Innervation pilttl!m. Because the nerves In ttte trunk do not form plexuses, the radiou~r innervation patb!rn continues into the peripheral territDry of a artaneous nerve (T2- T12: see B). It un be seen that afferent flbers from the sympa1hetlc ttunk reach the peripheral nerves distal to the roots. This explains whyradlou~r lesions .are usually not associated Mth autl:lnomic deficits in the affected clermatomu. E Pftssure on spinal nl!nle I'OCitl from 1 hemlltied lumbar dTikofL4/5 A herniated Intervertebral disk may exert pressure on the spinal nerve root or cauda equlna. The disk consists of a antral gelatinous core (nucleus pulposus) and a peripheral ring of fibtoc;'lrti~ge (anulus fibrosus). When the anulus flbmi~JS Is damaged, mmrial from the gelatinous core may be extruded through the ring defect and Impinge upon the root it Its entry Into the lntervenebril for.1men. This Is,. frequent cause of radicular symptoms, whkh 1\ave two gr.aclel of sewr!ty: • Irritation of the nerve root In the region of the Intervertebral fora. men. This leads to pain in the lcwback(lumbago), potentiallyaca:un· panled by pain radiating Into lfle lower limb In the dermatone of the .affecll!d root (sclatka). • Alarge disk he!"nlatlon may compress the dors.alandtorventral spln.al nerve root. causing- pain in addition to $C!I\SOfY deflcib and (if lfle ventral root Is affected) motor deflctt:s.

LS wrtl!bral body

;a PosteroiiWr;~l disk heml;rllon it the L4/S level. This damages the

LS root passing behind the herniated disk but not the descending L4 root. which has already entered the lntefvertl!llral foramen it !hat level. As a ~lt. the sensory deficits are maniti!sted in the LS dermatome (see 1). Only a far ~ter.rl disk llernlatfon will damage lfle root !hat exits itthe same lewl as the affected disk. b Postl!fomedlll dllkhemllltlon itthe L4/51evel. The material hemlatzs through the postl!!riarlongitudin.alligament and impinges on the cauda equlna. Cauda eqvltl
345

Neuroai'H1tomy - - 12. Functional S}tmms

12.11 Radicular Lesions: Motor Deficits A lnd'lc:ltormuJdesofl'ldiC\IIulesTorw-ldlm..dH iind dliphl'illgl!l (after Kure) Willie a lesion ofthe sensory doJYI roots leads to sensory dlsturbinces in specific dermatornes (seep. 344 and c. p. 345). a lesion of the mottJr wntrol roots will c.1111e weakness w deftlop In specific musdes. Just as thealfecteddermilt0melndlc3testlleslteoftllesensoryrootleslon,the affected muscle Indicates the level of tile damaged spinal cord segment or its root. The muscll!l tflat are pte
C4 ~ Dfpeln orsensorydlllllr1Hina

Shoulder

lndko*w mUid•

Diaphragm

. . . . . . . .lllhedby• ............

None

lnnew.~tlon.

j

I

'--.,_Pronmt te~s

--®

I

cs

C6

.......,

Lateral and posttnor side of shoulder. anlinlltl!ral side of plllldmal forearm

Dorsoradlal upper arm,

radial forearm -lflumb

--dJitllrcl (fourltl) finger

lnclc8lermlllde (and other

(i) DeltDid

® Blaps bradln

® Trfaps bradlll, hand and

al (Bleeps brachll)

® (lradl!oradlalls)

lJialfon of pain

·--" .. ........."*,

C7

Cl

Posterior Side of upper arm. -nsorsicle of forearm

to small finger and ring finger

dlgbl II~ and ext81SIIfl

Ulnar side of hand ~ding

Hypothenar, ulnar digital flexoR

Clllhenar musc:lel

{ll'lceps brachll, pectoralis

(!) Pecm~:alls major(.trnphyof

major-abdominal part)

sll!mocostal pa-t)

Blapsreftu (BradlloradlaiiS reflex)

346

Blaps reflex (Bradllorad!alls reflex)

Triceps reflex

Triceps rellu

(11'6mner reflex)

(11'6mner~

®- -

L3

L4

L5

51

Anterior side ofthigh. passing obllqwlyd-nwanl f111111 tt. ;~pproxrmaw 1-1 of the trochanll!riD the medial side of the knee

Posterolateral thigh. extensor side of lcnee ID ant.vmedl
Postel1or side of thigh. r.t.ral side of knee. ant.nl· lmr;~llower leg. dorsum tAfootto blgtoe

Lm!ral surfaat tA thigh and calf, heeiiD lateral edge of foot

~

(.!) Quadriceps femoris

0 Quadriceps femoris,

(e... other

® Extensorhalluds longus

(Mductors)

especially the vastus medialis <J> (Jlbl
(!) Tlblalls anl!eriOr

®Triceps surae, pen~nll, thlghfl-rs ® Gluteus maximus

Quadriceps reflex (Adductor refln)

llblalls pos481or rdlex

LoatlenofPIIn «.-y

..........

.........

..,.....mllldes)

........bollhecl

......

II¥asegmtntal

Quadrloeps reftex (• pab!llar tendon reflex • kn-Jerk reflelc)

8 Prindp;~llndiAtor mlllldes of thuplnal and stQments The table lists thetypiClll rnd1Cli1Jir muscles for each cord segment.

llfceps surae reflex (• Achilles tendon reflex • .ank~jerk reflu)

C atnlcal manll'estltlons of IH!fYI! roottrrftatlon • Pain In the affected dermatome • Sensory losses Ill the affected dermatome • lnaetsed ptin during mughing. sneezing. or stn~ining

....... Cord

• Pain fibers more ...ry affecmcl th.an ather sensory ftbers

C4

Dl
C5 C1

DIIIDid Bleeps brac:hn Traps br.achll

C8 Ll LA LS 51

Hypothenar muscles. long digital ft-rs on ulnar side Quadriceps femor1s Quadrlups femoris. vastus medialis Extensor hallucls longus, tibialis anterior Triceps surae, pen~nel, glumus mulmus

C6

® Gluteus medius

• MoiDr defldts In the lncllaiDr musdes of the segment • lldelii!S auodalal with the atredad segment are absent or dlmllllshecl.

347

Neurot~I'H1tomy

- - 12. Functional S}tmms

12.12 Lesions of the Brachial Plexus

= --"..-=-----7-: - - - - - - lcngthonldc "~

Axillary ----'y;;.=''------:li~j;'!:.....

nerve

MLIS(uloClltlneolll nerve

lllle
- ----7- - --H--

(-

----:7-----i~~N;}'-,

~~I Cut.lllt!OUSileM!

A BriiChllll pltwl pel'lfw'lll Anterior view of the right side. lesions art- clrded. By ddlnltfon. two forms of brichlal plexus p.;~ralysls irt' distinguished: upperbrachial plo:us pGralysls, which Is caused by a lesion of the CS and C6 ventral r.ilml (see C), and lrMWbn'ICitiol plexus pat'Qiysis. which is caused by a lesion of

348

the C8 and T 1 ventral rami (seeD). C7 forms a "wabershed• betwl!!en the two forms of p.;~r.illysls and Is typically unaffected by elttter form. A complete lesion of the brachial plexus mi)l ilso occur In severe triuma.

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

8 Sltlioflllllllfllnb!'lldiill plaxusp;nlysls

A br;u:tllal plexus lesion iffects the ventral rami of severill spinal nerves, whkh trinsmlt afferent signals to the pleJWs. Because the wntrlll riml arry both motor and sensory fi~. 01 ~i;al pii!XUS lesion ;~lwiy$ ause:sa combiNiion of motor and sensory deflc:IU. The resulting p.1r.rl· ysls (seeC} Is alwiys of the flaccid type because of Its peripheral nature (•lesion of the second motor neuron).

C Exolmplt: uppl!l' b!'llchtal p'-a p;nlysll (Erb's p;~lly) This condition results from a lesion of the ventril riml of the C5 ind

C6 spinal ner'YI!S, causing paralysis of the abducmn and external robtors of the shoulder joint and of the upper ann fle111:1rs and suplnatw. The ann hangs limply at the side (loss of the upper ann flexors). and the p.1lm faces backw.ud (loss of the supinator with dominance of the pronators). There may also be partial par.alysls of the ex!l!nsor musdes of the el~ joint and holnd. Typical CiiSe$ prvent with sensory dinurbances on the lateral surfice of the upper arm and fore01rm, but tilese signs may be absent. Afrequent cause of upper brachial plexus p.1ralysls is obsb!tric trauma.

Lzrtmaland saiMirnlands

Hart

lung

D E:Qimple: • - br~~chT• pi~ p;nlysls

(Diflline·ICJumpb p;~lly) This parilysls results from i lesion of the ventril rami of the C8 ind T1 spiNI nervel (see A). It affects the hand muscles, the long dlgltil flexars, and the fl90r musde:s ir1 the wrist (daw hand with atraphy of the small hand musdes, ;a). Sensory disturbances affect the ulllir surfaces of the foreinn ind hind. Beause the sympathetic flben for the

head leave the spinal cord at T1 (b), the sympathetic innervation of the head Is also lost. This Is manifested by a unllomol Hon!ef syndrome. ch•racterlzed by miosis (contracted pupil due to p.1r.rlysls of the dilator pupillae) and narrowing ofUie p.1lpebr.ill ftssure (notptDsls}due to a loss of symp.1thetic innervation to the superior and inferior t.ilrsal muscles. The na..-d palpebral fissure mimics enophthalmos (sinking of the eyeb.illllnto the orbit).

349

NftnuarKltomy -

12. FunctlonoiSptems

12.13 Lesions of the Lumbosacral Plexus

A Lumbottc,.. , . _ Mtlerlor view. The lumboncnl plexus Is dlYlded Into alumbn plexus (T12-t4} and sacral plellll5 (L5-S4). Nofr. The ni!MS of the lumbar j»rt (yellow) j»U ~nteriorly while those of the sacral part (green) j»U postatorly. The connection between the two parts of the plexus Is the lumbcnKr.~l trunk. Because the lumbosacnl plelii.IS Is In il protzcted loation deep within the pelvis, it is less commonly ilffectzd by lesions thiln the br.~­ d!lal plexus, whld! Is mud! more superftdal. The Iumbosacral plexus may be injured by pelvic r1ng fractures. a Siltr.ll bone fracture. or hlp fnct1Jres, or as il compll~on of hlp repla~ ment.

0...1---===--

Lumbasllcnl

trunk Sl

w.m-ond otropltfofthe hlpftan,

lcneeemnsan, and~

rotltDIJ and adduc:tarl
SUpel1ar

glu!Yn8W!

r-......I!OL---.::lW~"""~-- Inflrior

glu!Yn..w

•

b

I Lesion ofthlllft lumb.r pluw (T12-L4)

The dominant future of this a>ndition is femorill nerYe j»l"llysls lffectlng the hlp flexors, knee extznsors, and the I!XI:emal robtDrs and adductors of the thigh (a). A 5eru0ry deficit Is found on the anll!mmedlal upect of the thigh and c:.alf. The lesion also disl'llpts the sympathetic fibers for the 1~. which ar1se from the lumbar cord and j»U thraug h the lumbar plelWS. The dlniCill manifestations (b) indude; lncreliSed w•nmth of the foot (loss « symj»tlletic vasoconstrictiol'l) and anhidrosis on the sole of the foot (S'ftatlng Is absent because of loss of sympathetic lnnervitlon to the sweat: glanc!J). When ~ng is intact. t he ninhydrin tzst Is positive (footprint on a sheet of paper stains purplewith 1s nlnhydlfn solution}. Nofr. ~nl~ In the limbs are recognized by mm~rtson with the UNII'edl!d side.

350

Nf!uiOGDGtomy - - 12. f'undiomltiSymms

\...::~~

Antl!rlor CW!neous br.~ncheoJ

Saphenous "~

D l.etlon oftfle r'lghtt.unl plexul (L5-S4) This lesion presaru clrnle<~lly with po!VIysls of 111!sclotJc nl!m! and Its two main br.;mches, the tibial .md common fibular nerves, whkh .ue jointly afred:l!d. The I'!! suits are loss of planbr flexion (tibial nerve paralysis. Inability to walk on !he toes) and p;~ralysls of the foot and toe extensors (common tlbular nerve, 51leppage g.;rit: thl! patient must raisl! thl! knl!l! abnormally high while walking to avoid dragging the toes on !he ground). Sensory disturbances ire noted on the postl!rtor surfaa!s of the thigh, lower leg, and foot. Beause the superior g/11· teo/ nl!'nlrls lnvollled, the glutleus medius ind mtntmus ire also paralyzed. These two muscles stiblllze thl! peMs of the Stitlonary side during gait. When they are p;~raly.zed, the pelVIs tilts wward the swinging leg, prodiiCing i •waddling• galt(known also as a positive Trendelenburg sign). The supertor glut2al nerve also innenr.ates the tensor fasci;le latae. which normally acts In the same manners as the two gluteal muscles. Specific categories of perfpher.rl nerve lesions are desert bed In the volume on Gener<~l Anotomy ond Musculoslcflnol Sys· h!m.

C Musalln i!rtdalt31'11!ousdlltrtbuUon oftMfemorill nerw{l1-L4) Antel'forvtew.

351

Neuroanatomy - - J2. Fundfonai S)lmms

12.14 Lesions of the Spinal Cord and Peripheral Nerves: Sensory Deficits Onrvlnrllfthc natduw unlb(aftw Biihr ir.dl1tltsdter) Two questions should ~ ildd reued In tne dl<~g nastfc ewluaUon of

splnill cord lesloru: 1. Whit strud!Jre(s) wttnln the cros:s~ of the spiN I cord Is (ilre) ilffectecn This 1!. detannlned systl!m~ally by proceeding from tne periph8)' gf the tllrd tuwilrd tne ~. 2. At whit level of the spinal cord (In longitudinal section) Is the lesion located?

In these units we will limcorrelate 'iilrlous defldt pilttmls (syndromes) with the strud!Jres In the avss-sedion of the sp.I NI cord. We will then discuss the level of the lesion In tne longitudinal or aanloeo~udal dimension. Since these syndromes pmentwith def'ocits that mult from dam~ge tD spedllc <matomlt-ill structures. they can be explo1lned In an
A SpliNII ~ngnan .,ndnamoiiMtnt.d far an llalilted lesion llfT6 As part of tne dorul roots, tne spiN I gilnglla il re coi'ICI!rned wttn tne transmission of sensory lnformiltlon. (Recall tnat: tne ganglia contain tne perikarya of the first sensory neuron.) When only a single spinal gan· gllon Is affected (e.g •• by a viral Infection such as herpes zmWr). there· suiUng pain and parestflesla 1re limitEd tD the sensory distribution (der· mat:ome) of the ganglion. Ilea use the dermat:Dmn .sllow considerable DW!rlap. adjacent dermatames can assume the function of the affedl!d dermitome. As a result. the area thit shows <~bsolute senSOI)' loss, ailed the •autonomous are01• of the demutnme, may be qul12 sm;~IJ.

I Doniil roat syndn~me lllustrmd fur a lesion ill: the C4-T61eW!I When il lesion (trilumil, degenerii!IW splnill chilnges. tumor) ilffects multiple sua:ess~ dorwl roots n in thiJ C".Qmple, complete sensory loss ocaJrs In the IIRc:ted denmat:Dmes. Wha-t this s.eruory loss affects tne ilfferent limb of il reflex, thilt reflex will ~ absent or diminished. If tne sensory dorlill roots ill!! lrtltilted but not dluupted, ill In the ase gf a herniilted i~br•l disk. s~ pain l"niiY sometirne5 be Ill"" ceiYed In tne ilffected dernniito.me. Beciluse pain flbels do not 0\ltlfap OlS mud! ti otner sensory fibers, tne examiner should hiiVI! no dlfllculty In identifying tne affected dermatDme, and thus the corresponding spinal cord segment. from the mUon of the pain.

c

Pain, p;orHihHia

I Anl
cor11mspna1 I !aCt

LDuahll senmry qallf..

~rtor hom syndrome •lu...-ated ror •lesion

iltthoCS-CIJ.wl This lesion, IIR il dorsal roat lesion of the spinal nerves, Is charactertzed by a segmental palll!rn of sensory dl1turbilnce. But wtth a postl!rlor horn lesion of the spinal cord, u nUke a dorsiI roat lesion, the resu ltlng sen· sory deficit Is Incomplete. P~ln and temperature sensation are abolished In the dl!lllllatomes on tne lpsllmral side be a use tne flrst peripheral/ a!nrent neuron of the latenll spinotnalamic tract is relayed in tne posterior hom, which Is within the damaged <~rea. Position -and vlbr.ltlon !.el\5e are unaffected beause the fibers for these sensory quaiiUes are both conveoyed In the postlertor funiculus. Bypassing tne posterior horn, tnese fibers pass directly via the postl!riar funiculi to their synapses In the nucleus gracilis or nucleus cuneatus (see p.276). A lesion of tne anterior splnoehalamlc tract does not produce strllc· lng dlnkal .!olgns. The deficit (loss of pilln and temperat:u re sensation with tnsei"Vlltion of position •nd vibo;otion SICI\se) is ailed a (/;ssoc;Wd mi:IIOIY lou. Pilln and temperature Sa~siltfon are preserved below tne lesion because tne tracts In the whlb! rniltil!r (lilter.ilsplnothilimlc tr.1ct) ilre undarnilged. This type of dlssoclilted sensory loss occurs In syringo~.lia, a congtnital or acquired tllndition in which threre is an eJCPll nded avlty In or nl!ilr the Caltrill canal of the spinal cord. (AccordIng tD the siJ1ctest terminology, I!J!Panslon of the central canal Itself 11)1!romyellil).

352

C4-Tii

--~ayrtOJW.

- - lmpalrm...tof

lmpamontof

Tl

D Lallonvftl'lll pOIWtorfvnlalll•ti'IIITIMI A lellon of the posterlorfUnlaJII (see also p.275} Is chiriictel1zed by a loss of;

• Position sense. • Vlbr~on sense, and • Two-pointdiscriminatfon. These deficits oa:ur distal to the IHion, hence they involve the legs ind lower trunk when the IHion Is at the T8 level. When the legs are ollffectl!!d, as In the present example, tfle lass of position sense (mediated by proprioception, see p. 179) leads to 1n unsteady galt (<~taxli). When

consdcul

~point

plqlltoa-pllon

dlsclltnlretloft

the ;um 15 iffected (not shown here), the only dlnlal finding Is sensory Impairment. The IKkoffeedb.Jckto the motor systl!!m also prewms the precise I!Rractlon of different musde groups during flne movements (iiSynergy). Ataldi results from the fact tNt lnronmatlon on body position is essentia I for carrying out m_,..ents. Vision can (partly) compensate for th!J lou of lnfomnatlon when the eyes 1re open. and so the ataxia worsens when the ~ 01re dosed (Romberg's sign}. This RIISOI)' lltliJricl differs from ~rcmwo in that the litter e~nnot be c:ompen· Sited by visual control.

_ _ ..,..of p<~lnand ~m.,-n

fe'l~

C4-T4 E C.., m1tbrsyndrame lllultnted r.r •lesion 8ttlleC4-T41evel This syndrome ruults from a pathological process (e.g., 1 tumor) In 1nd around the c:ennl canal. All nets that c:rm1 through tfle gray ll\OIItter are dlmaged. I.e .. the amrtor and litEral spinothalamic tracts. The result Is a dlssodated 5111sory loss (loss « pain and temperature sensation with presev.rtion of position, vibratiOn. and touch), in this case lnwlvtng thu nms and upper chest (com pare with C). A relatively llrge

lesion may iddiUonally Olffect the ararlor horru, whim contilln the alpha motor neuron, nusing a flacxid paralysis in the distal portions of the upper limb. An em1 llrger lesion 1M)' concomitantly ~ the pyrllmldil trut, Cluslng spastic paralysis of the distal muscles (here In the le!Pl· This syndrome may rault from syrln~li (see C) or tumors IOCAIJ!d near the cennl CIN I.

-Atlldo,~tfllll· lmpalm~ent

ofamsclous

" F Com.,IIIIMI ,.1_ vfthe pllltlrtor funla.IIJ """ pyr<~mld<~l tiKt dlllltnt8d fur •lellan•the Tli level A lesion of 1M pomrlor fun/evil leads to loss of position and vibration sense. Aconcomltlnt pyrvmldolmx:t ~slot! additionally leads to spastic para!y,is of the legs and abdomin<~l musc:les bel- the ~ dermiitome,l.e., bel-T61n the e:Qmple. This predominantly anlc:o-

pRJprtoaptlon

thoradc lesion typically ocaJrs In funicular myelosis (vltlmln 812 defldency), In which the posteltor funlaJIIare atfec:t2d Initially, followed by the pyrllmldal tract. This diJftll!!lJ charac:ter112d by degeneration of the m)"'!lln sheaths.

12.15 Lesions of the Spinal Cord and Peripheral Nerves: Motor Deficits

C7-CI

A Antellarham .,nchlme llultrwbd faralalan •ttlteC7-CIIevel Dimage to the motor antaior hom cells leads to lpslliter.ll p;~ralysls, In this case Involving the h~nds and forN nm muscles because the lesion Is at C7- C8 and these segments lnnerv.~te the mumes In thIs reg Ion. The p;~raly.sls Is flicdd because the al phi motxlr neuron that supplies the muscles (lower motor neuron • s«
neurons from more than one segment (seeA. p. 270), damilge to i single ~egment may l!ad only to muscular we.lcness (paresis) rather thal'l complete parilysls of the iffected muscle group. When the lateral horns are addiUonally Involved, decrused sweating and vuomo!llr fundfon will abo be noted becaURthe latenl horns contain the cell bodies olthe sympathetic neurons that subseM: these functions. This type of lesion may oa:ur rn poliomyelitis or In spinal muscular atrophy, fur example. These relitively rare diseases are relentlessly progressiYe.

B CGmlllned l•on• of die MIIHTar ham .,..IIIRnl Cllrtk:DipiUI

No~: When the second momr neuron In the ant:elfor horn Is aii'IYdy d1maged (flacdd p;~ralysis), an 1ddilionalleslon of the lateral c:orticospln<~l tract it the level of the same segment will not produce 01ny r . tlceable effects. This lesion pattern occurs In 1myotrophlc lateral sderosls. In whim the first cortical motor neuron (pyramidal tract lesion) and second splnil motor neuron (interior horn lesion) both undergo progressive degeneration (I!Ciology unclear). The end stlge Is marlced by addiUOnilllnvo~ ment of the motor cr~nlal nerve nuclei, with swallowing and spealclng difficulties (bulbar paraiy,ls).

lrKt

These lesions produce 1 combination of flaccid 1 nd sp;~stlc pilrl lysis. Dimage to the motor Interior horns or •~ower• motor neuron (• sec:ond motor neuron) nuses flaccid p;~ralysls. while a lesion of the literal cortlc:ospln~l tract or •upper" mo!llr neuron (•first mo!llr neuron) Cluses sp;~stic parollysis. The degree of injury to both types of neuron may be highly Virlible. In the example shown, in anterior horn lesion at the c 7 - c 8 le\11!1 h~s caused flaccid pilr.l lysis of the fore;jrm and hand. By contrast, a lesion of the literal corticospinal tract at the TSieve! would cause Spilstlc para lysis of theabdomiNia nd leg muscles.

C Cardaasplnallnlc:t~plllrome ProgreN~ spilstic 111inal pilraiy,is (Etb-Oiarwt di-) is characb!rlml by a progressiYe d111eneratlon ofthe c:ortlul neurons In the motor cortn with lnaeaslng falluno of the corticospinal pathways (DONI degenmltlon of the flnt motor neuron). The course of the disease Is marlaed by il progressl~~e spli!Stfc p;~ralysls ofthe limbs that begins In the l~egs and ~nt\lillly
354

Neuruanatvmy -

12. FunctlonaiSysmns

-

- - l.otonl funlculor

D Comlllneclletlons of the postertor funlmu~o

splnocerellel..r tr.cts. •nd .,...mW.I trKt This syndrome begins wltfl destnJctlon of the neurons In the spinal gangll.a, whkh tnnsmlt Information on conscious position sense (loss: at
sensory atura (IKkoffeedbacktothe motor system, seeD, p.353). But the lesions additionally afiK1: the spinoce<1:bellar truts (uncofOKig~~~s propr1ocepdon), lnju ry tD which suffices tG cause ataxia, ind so this dual Injury auses il parucul.ar1y severe loss tl conscious and unconscious propr1ocepdon. ThIs Is tile rna In cllnle<~l mlllre tl tile disease. Sp~stlc po1 ralysls also develops as .a result of pyramidal tr.act dysfunction. The prGtutype of this disease is hen:ditllry Friedreich ttaii, which has severa IVllrlants. The gene hilS been loaItzed to chromosome 19.

- - loB !lipan and temponllii'O!

oenslllal

--Lauaf•ll

sonoary quolltles QnT10

dennacorne)

H)1lellhesll, k>llsafcanldaL& proprtoctpdOft

T10

E Sp!Jal hemlplqla tyndi"DDnnl! (lruwn-Mquii'CIIJIIdrame) llluslnted tor •Iaon lit the T 1o llllwl on the left side

Hemisection of the spinal cord, though uncommon (e.g., in stab inju· r1es), Is ;m I!JI[elllllnt model for wtlng our underst.andlng ~the function and coune of the nerve tracb in the spinal cord. Spastic paralysis due to 1nt2rruptlon of the pyrtmldallnlct (see footnote on p.343) occurs on the side of the lesion (.and below the lew!l of the lesion). The lntenu~ lion of the posterior funiculi (pathways far conscious pruprioaption) a uses t loss of position 1ndvlbr.atlon sense and two-point dlscrlmllli· Uon on the slde~the lesion. AftMo spln.al.shock his subsided, sputlc po1· ralymdevelops belowthe level ofthe lesion (here lffectlng the left:leg). Of murse, this p~r.Jysls does not produce iln mxla lib th.it described

following Interruption of tile posterior fu nlcull. Destruction of tile ;~I pha motor neuiWis In tile loally damaged segment (In this case T1 0) leads tD ipsilateral flaccid paralyJis usociited with this segmlllnt. Because the iiXDns of the literal splnotht ~mlc tnct hwulreacly crossed tD the unaffect2d side below the lesion, pain and temperature sensation are pn!!· served on tile lpstlotwul side below tile lesion. These two types of sensation ilre lost on the contmlatmll side. ' - r , beause the crossed iiX· ons on the opposite side h;,ve been intenupted at the level ofthe lesion. If splnil root lnlullon occun It tile level cl the lesion, r;~dlcular pain may oa:ur because of the d-endlng coune ofthe SMSOry (and motGr) rvots In tile segment abaft the lesion (see I, p. 345).

Neuroai'H1tomy - - 12. Functional S}tmms

12.16 Lesions of the Spinal Cord, Assessment

A Deft db c.~~ used by complete cord le.tlont lit ,_rfou•leweh Hi!lllng eJq~lored the manlfe5t.1tlons of lesions at dlfferart sites lr1 the aoss-sectlon of the spiBal cord, we 1M! I !lOW consider the effects of lesions at various le...els of the cord. All ~mple is the paralysis caused by a aJmp/ewsplool oonl k$1or1. which occurs acuW!y
lesions ol the lumblr c:Qrd, a distinction is drawn betwc!c!n epicon111 syndrome (L4-S2) .ilnd conus syndrome (Sl d~Mnw.!nd). Eplconus .syndrome Is dl.ilracterfzed by a flaccid paralysis of the legs (only the roots are affected, auslng pe!1pheral paraly.lls). and reflex but not conscious emptying of the bladder and ~m is pneserved. Sexual potency is lost. In alllUS syndrome. the legs .ilre not paralyzed and only the foregolr~g autonomic dlrturbances are present. The motor defldts described here are also associated with sensory defldts (see B).

B Deftdts auocTatll!d wtth c:Qmplete spl'nll can! letlont et Ylrtous lewb (after Rohbmm) l.wloflllloll

MOIIDrdlftcRI

Stnlorydelcnl

AIICIInomlcdefldla

Cl-0

• Sensort IO$$ from occiput or rnandlbulilr borderclownw.ilrd • Pain In occipital region, back« neck. and shoulder region

• Reflenlse\!ral functions (bladder, bowel) With no voluntary control • Homersyndn~me

• Sensort 1055 from clavicle or shoulder downward • Sensort 1055 from upper chest wall andbackclownw.ilnlandonthe <1rms (sparfng the shoulders)

•

Seea~

•

Seea~

oord lesion)

• Quadrlplegr, • Paralysis tA nuchal muscles • Spastldty • ~splmory paralysis (Immediate cletth if not artificial!, wnlllated) • Quadriplegia • Diaphragmatic r.splndlon only • Quadriplegia • Diaphragmatic r.splndlon • Spastldty

Tl-TS

• Paraplegia

• Sensort IO$$ from Inside of forearm. upper chest wall and back

• Reflec function of bladder and rectum • Erection wlttlout wluntary conlnll

• Sensort 1055 from affected r-1 In c:hestwall and back • Sensort 1055 from gtOin region or frantof thigh, depending on site of lesion • Sensay lcm from"-« thigh, dorsum offoot. sole «foot. or back of th~. depending on site of lesion • Sensort 1055 In perfanal regiOn and Inside« thigh

•

(high cervical mrd lesion)

C4-C5 C6-C8 (~eM. cervlal

• Oecreued resplratorywlume

T5-T10

• Paraplegia, spastfdty

T11-L3

• Paraplegia

l4-S2 (eploonus. spinal nerw

• Distal paraplegr.

roots p.arary.d)

S3-S5 (conus)

356

• Nodeflclt

Seea~

• Seeabove

• Flaa:ld paralysis of bladder and rectum • lmpotenca •

Seea~

1~----: ~~=7'---

(C8-T1)

AI>Wclrlrpolllds brevis (C8-T 1)

~~b~l ----~--~

(C7-CB)

Deltoid -~;r.,r--r. (C4-C6) Trapezius (C2-C4)

_ _,.;..__

Diaphragm (C3-C5)

ThonKic conllelon

l.lllfs.slmus 6cn1(C6-C8}

Conuscraudl

• c

DttennWng the 11!'111!!1 oftpiMI cord leilont

;a ""-d11 ind Ule spln;al cord A!llmen'tf thirt lnnerwte them. MoJt

mu5eles are mullisegmental,l.e., IIley receive lnnerwtlon from sever.al spinal cord segments. Thus, for ex.lmpil!. a lesion irt the c 71evel will n~t neceswrily a use complm par~IY$iS of the lati$simus dor,;, because that muscle Is aiJO Innervated by C6. This Is not the case

equlneletlon

'Nith the "indicator musclel,• which are supplied almost exclusively by a single segment (see8. p. 347). A lesion irt the L31evel, for eMmple. 'Will ca111e almost complete paralysis of the quadriceps femoris because that mu5ele Is Innervated almost ent111!1y by L3. b The degree of dllabllty varies, depending on the level of the mmplete cord lesion.

357

Neuroai'H1tomy - - 12. Functional S}tmms

12.17 Visual System, Overview and Geniculate Part

Optic

·~

utenl wntrlclt

Optic tr.lrt

OptlcnetW

utenl QeMIC\1· lite body

\

l'ld'6ent

Tlird

light

n~rwt:

g~ngllcn

~Is ~nd n~rwt:

blpdarCII!b

con due.tfan

011'61

•

Oplk:

dllasm

~s

loop

Optic llldltlan rw UPP'!fWUIIfleld

?

I~T¥~Ube

--Strtm!

I

First n~rwt:

nxlnnd COMe'!

Str'laof

c

b

Clenna~

A OW!mew afthe WUII patfrway

L1'lenl genh:uw balfr: Ninety perant of tile alGOilS of the third neu-

Left lateral view. The visual pathway extends from the eye. an anterior prolongation oftile diencephalon, bickto tile occlpltll pole. ThiiS Iten· compassesalmorttile enUre longi!IJdlnal aXIs of tile brain. The principal stations are as fallc:lw$: ll.ltll'liL The retina contains the flm three neurons of lfle visual path· way (b):

ron (•90%oftheoptlc nei'Yt'flbers) terminate In tile lateral genlculatt> body on neurons that project t» tile strlatt> area (visual cortex, see b~ low). This Is tile !lfllkuiGil! port of the llfsual pothwoy (discussed here). It is cancemed with culll'C1'ola visL~al perception ;and is conveyed by the later.~! root of the optk: tract. The rem;rlnlng 10% of the third-neuron ;rxons In tile wual pathway do not terminate In the lateral genlculatt> body. This Is the nongenlt:ulate port of the llfsual patlliW')' (medial root, SH8, p.361}, and itssignal$ane not consciauslyperceill1!d. OpUc ndlatSon ;rnd Wuill -ux (str1ilte are;r}: The optic ndlalfon begins In tile latl!r;rl genlaJiate body. forms ;r band that winds around the Inferior lind posterior horns of tile later.!! ventJfcles, .and termlnllti!S In the lllsual cortex or strlatt> "re;r (• Brodmann are;r 17). Loc.rted In the occlpltlllobe. the visual cortex c;rn be grossly Identified by a prominent strfpe of whitt> matte!' In the otherwise gray cerebral cortex (tile stria of GenBari, see c). Thh1/lhlt:e stripe runs parallel to the brain sul'faa and Is shclwn in the inset. where the gr;ay matn!r of the visual cortex is shaded light red.

• First neuron: photoreceptor rods and canes. loc.rted on the deep

relfnal surt.lce opposite to the direction of tile Incoming light ("In· version of the retina"). • Secvnd neuron: bipolar cells. • Third neuron: ganglion cells whose axans are collected to fonn tile OptiCnel'l/e. Optic n - . optk ellJan, and optic trlld:: This neural portion of tile wual pathway Is part of the centrlll nei'I/Ous system (optic nerve • tr.~nial nel'l/e II) and issuJTOunded by meninges. Thus. theopticn- is actually a tract rather than a true nel'l/e. The aptfc nerves join bdowthe base of the diencephalon to fonn tile optic chiasm. which til en d!llfdes Into the tv..o oplfc tracts. Each of tllese trllcts dlllldes In IIJrn Into a lat· eral and medi;!l root.

,....

---=~-

D D

L8't hllf of 'flsuallleld

RJQht ~~;~Ifof~~tw;~llleld

Ni5ilvl!iuillleld ofr!Qhteye

- - Ten'9flr.ll~sualfleld of light~

I Rapr-.entil\lon of Nch vtaal flllld tn the CDnt.r.llater.irl 'WtsuaiCDrtu Superior lltew. The light rays In tile nasal part of each \llsulll field are projected t» the tMipOI!ll half of the retina. while those from the tern· poral part;rre projected to tile retln;rl h;rlf. Bec;r~&Se ofthis ;rrrangement. tile left half of the wual tleld pro}ects to tile visual cortex of the rtght «cipital pole, and the right half projects to the visLI:!I mrtex of tile left «dpltal pole. For darlty, each visual tleld In the diagram Is dllllded Into two halves. and the re;rder should understlnd tills basic dMslon before we explore how tile lllsual fields are diYlded Into four quadrants (C). NoU!: The axanal fibers frDm the natal half of each retina cross to tile apposite slde it the optic chiasm and lflen triVt'l with tile uncrossed flbersfromthetemporal half of each reUna.

358

6""-~-+--

Lmral

genlalm body

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

Maallr >lsual field

D lnformahfsval 1\'eld exo~mlntlfon with the confrorltlltTon test Th~ visual field t:!Xllmination is an essential step In the ex.amlnatfon ofleslons of the llfsual pathWliY (seeA.p.360). The confrontltlon test Is ;m fn(onnoltert rn which the examiner (with an intact visual fteld) and the patient sit face-toface, cover one eye. and each fbces their gaze on the other's open eye. aeatlng ldentfca1111sual axes. TheexamlnerthenmCM!S hlsorherlndex linger fn:Nn the outer edge of the visual fM!Id toward the cenwr until the patient signals that he or she can see the finger. With this test the ex<~mrner can makle a g~ assessment as m the pre- ;and appraximate location of a possible visual field defect. The precise locitfon ;md extent of a llfsual fleld defect can be dete!'mrned by pe'lmetry, rn which points of light replace the examiner's linger. The re$Uib of the test are entered In dlarts that resemble the small dlagr.~msln c.

Optic--~

c:hll!m

t

C TopogNphk: organl'latiDII of the geniallite part ofdie WUIIplthwily The fovea cenrralls. the point of maximum visual acuity on theretlrlil, has a high receptor density. Acalrdlr~gly, a great many axons pass centrally frDm its reaptors. ;md so the fovea central is is representl!d by an extA!f)· tfonally large area In the visual cortelc. Other, more perlpher.~l portlotu of the retfrlil contain fewef receptors ;md therefore fewer axons. result· lrlg In a smaller representational area In the llfsual cortex. Note Only the left half of the mmplete visual field is shown. It is sub· divided Into four quadr.~nb (dockwlse from top left in 1): upper tempo· rat. upper nasal,lowernawl. and lower temporal. The representitlonof this subdMslon Is conlfnued Into the VIsual cortelc. 1 The three zones that make up a particular 1lbull hemllleld (left, In this case) are each lndlc.ltl!d by color shading of decreasing Intensity:

• Thesmallestanddarkestmnelsiltthecenterofthefoveacentralls; itcotn!sponds to the antral visual field. • The largest zone Is the macularYisual field. which also contains the "bllndspot" (= optfcdlsk.see:l). • The •temporal crescent" repnesents the temporal, monocular part ofthevisuallield. • Note that the lower nasal quadr;mt of each visual fleld Is lndmted by the nose (small medial depression). :1 Beause all light that reaches the retina must ffrst pass through the narrow pupil (which Is Jlkle the aperture of a camera), up/down ;md temporalfnawl are elt.lctfy rewned when the Image ~ projectled ontothe~l\ll.

3, 4 rn the rnllfal part of the oplfc nerve, the fibers that represent the macular visual field fim OIXUPY a l;!ter;al position (3) and then move Increasingly tow.rrd the center of the nerve (4). 5 rn traversing the opac: diTIIIIITI, the nasal fibers of the optic nerve cross the mldllnetD the opposite side. 6 At the mrt of the optk tnd, the libel's frDm the corre.sponding halves of tile retinae unite- the rtght hallles ofthe retinae In the right tract, the left haiYes In the left tract. The Impulses from the right visual field finally terminate in the lefts!Jiate area. Initially the mawlarflbersconttnueto ocaJpya central postt!on lntlteoptlctract. 7 At the end of the optk tr.1ct. just before It ent2rs the lateral geniculate body, the fibers are collected m form .a wedge. 8 In the lltenl geniculate b~. the wedge shape is pre.served, the maaJiar fibers occupying almost half the wedge. After the fibers ;rre relayed to the fourth neuron, they project m the posterlorend of the occipital pole (•Yisual cortelc). 9 This figure s~ that the central part of the visual field is rep~ sented by the largest ;rre;a In the 'Wtswl_. compared with other portions of the field. This Is due to the large number of axons that run to the oplfc nerve from the fowa centralls. Th~ large proportion of amns is mntinued into the visual ro!Ux,. establishing a point·topolnt (retfnotoplc) correlation between the fove;r cenrralls and the llfsual cortelc. The other parts of theYisual field ;rlso show ;r polnt·topornt correlation but have fewer axons. The central lower half of the visual field is representl!d by a large area on the occipital pole above the c;rlcarlne sulcus. while the central upper half of the visual ffeld Is represented below the sulcus. The region of centr.lllltslon also oca; pies the largest area within the lmral geniculate body (see 8).

359

Neuroai'H1tomy - - 12. Functional S}tmms

12.18 Visual System, Lesions and Nongeniculate Part

Right

wualfleld Tl!mporal

Nasal

Tempor.~l

'

7

A V1111al fteld defects (scot.omat.J) ;md ttu!lr lout:~ on ;!long tile Willi patflway

Vosual field defects and lesion sib!s are illustrab!d here for the left visual pathway. Lesions af the Ylsual pathway may mutt from a large num· ber of n~rologle<~l diseases. The patient pm:elves the lesion as a visual dls!l.lrb.mce. Because the nature of the visual field defect often points to the locatio Aof the lesion. it it. cliAie<~lly important tD lcnowthe patterns of defects that may be mcountered. Division afthevbual field Into four quildrants Is helpful In deb!nnlnlng the loc.rtfon of a lesion. The quad· r.ilnts ate designated as uppt!r and lower temporal. and upper .ilnd lower na~<~l (M!ealso p.359). 1 A unllab!ral optic neJVe lesion produces blindness (.ilmaurosls) In the ;alli:!cted eye only. .1 A lesion of the optic chiasm caus;es bltmlporal hemianopia (as In a hor5ewearlng blinders) bee<~use ItInterrupts the flbers from the na~<~l portions of the retina (the only ones that CR)SS in the optic chiatm), whkh represmtthe temporal Ylsual flekls 3 A unilateral lesion of the optic tract causes contralateral homonymous hemianopia bee<~use It lnteiTUpts flbers from the l:l!mpO/Gl por· tlons of the retina on the lpsl'laU!r.illslde and the no.~r~lportlons on the opposite side. Thus the right or left half of the visual field is affecl!!d lru~ach eye.

360

4

5

6

7

NOll!; All homonymous visual field defects ire caused by i retrochlismalleslon. A unilateral lesiar\ of the aptic radiation in the anterior temporal lobe (Meyer's loop) le-ads tD contralatwal upper quildrantaoopla (a •pte-In-the sky"'defldt). This occurs beG! use the affectzd fibers wind .ilround the lnfenor hom of !he lateral ventricle In the temporal lobe and ate sep;~rated from the fiben that came from the lowet' half of the visual field (see p.358). A unllateril lesion In the medial p;~rt of the optic ridlatlon In the parietal lobe leads to contral.tteralloiNer quildranto~nopla. This occurs bee<~ use thefibencourse superiortotho$t'for the upperquadr;ant in Meyer's loop (seep. 358). A lesion of the ocdpltil lobe leads to homonymous hemianopia. Bee<~use the optic radiation fans out Widely before entering the Ylsual cartex, le.sions of the occipital lobe hiM! been described that sp.1re foolt
Nf!uiOGDGtomy - - 12. f'undiomltiSymms

_...,.....--- VISUiJI(strllltu~)

--~4-----r-------4-~A-4--~M~r«

thlllamus

8 Nongentculat.ep;ntofthe'llfsu;~l p;l\tlwq Approximately tOiofthe axonsofthe optic nerve do nottenn!nateon neurons in the lmral geniculate body for projection m the viswl cor· tex. Theya~nt!nue along the medial rootoftheoptlctract, forming the nongenlculakportofthevlswl pathway. The Information from the.sefl· ben Is not pnocessed at .11 conscious level but plays an lmportint role in the unconscious l'l!gulation of various vision·l'l!lated proce$Se5 ;rnd in vlswlly mediated reflexes (e.g .• the afferent limb of the pupillary light reflex). Alcons from the nongenkulare part of the visual pathway tl!mll· nate In the follclwl'ng regions: • Alcons to the supelfor colllaJius: transmit kinetic Information that Is necessary for tracking moving objects by uncoruc:ious l!y1! and head mavemenU (l'l!tinDn!ctal system).

• •

• •

speclfk nude! has not yet been accomplished In humans. and so the tl!ml*area*ls used. Alcons mthesupr.achiasmatic nucleus of the hypothalamus: infl1.1e111ce circadian rhythms. Alcons to the thalamic nuclei (optic tr.act) In the tegmentum of the mesencephalon .ind to the vestibular nuclei': afftrentftben for op~ lcinetic nysugmus (• jerky, physiological eye movemenU during the tracking offast-mO'IIing objects). Thls has also been called the "accessory visual system." Alcons to the pulvinar of the thalamus: VIsual assoCiation cortex for oaJiomcmw f\Jnction (nC!I.lrans are relayed in the superiorcvlliculus). Alcons to the parvocellular nucleus of the reticular formation: arousal funcdon.

• Alcons to the pretect;rl anea: aff'el'l!nU for pupillary l'l!SPOnses and accommodation reflexes (retlnopre!Kt31 sy5tem). Subdlvislon lnm

C Bnllnrtetn neflemet: dWc.al Importance ofthe nongenkulm: p;11rt ofthallfwiil p;~thw.ly Br.llnstem reflexes are lmportint In the examination of comatose patients. Loss of all brain stem reftexells con.sldel'l!d eVIdence of brain death. Three of these reflexes are described below: PUpll;uy n!llex: The pupillary reflex. relies on the non geniculate parts of the vlswl pathway (see p.363). The oift'erent ftben for this reflex come from the optic nerve. which is an extension of the diencephalon (since the diencephalon Is nat part of the br~lnstan, •br~lnstem reflex" b a somewhatunfortunateterm). Theeffa'entsfarthepuplllaryreflex.come from the accessory nudeus ofthe oculomotor nerve (CN III),~Mllch Is located in the brainstJ!m.Loss of the pupnlary refla may signify a lesion of the diencephalon (lntefbr~ln) or mesenccphalor1 (midbrain). Vestl11uJo.oallarmltx: Irrigating the ear canal with coldwater In a normal IndiVIdual ewkl!s nystagmus th.it beats toward the opposite side (aff'el'l!nt fibers ;rre canveyed in the vestibulocothlear nerve• CN VIII, effa'ent fibers In the oculomotor nerve- CN Ill). When the vestlbulo-ocular reflex Is absent In a comatose patient, It Is considered a poor sign because this reflex 1~ the most reliable dinteal test of bralnstJ!m funCtion. Camml reRa: This reflex. is not mediated by the visual pathway. The aff'aoent flbm far the reflex. (elicited by stimulation of the cornea, as by touching It with a sterile cotton -Msp) are conveyed 111 the 1rfgemtnal nerve and the efferent ftben (contraction of the orblaJiart~ oculi In nesporue to corneal irritation) in the f.acial neNe. The relay anter far the corneal reflex Is located In the pontine region of the bralnstem.

361

Neuroanatomy - - 12. functional Systems

12.19 Visual System: Reflexes

..

!/

Ollatls

'---+.-

Pllpll;lly

sphlnclllr Shortdlllry ntiWS

Lmril gonlcu~

body

-;...__ _ _....:...__ _ Nudtw ofoculomotor fH!fW (mediiI recllls}

Aru1!l--

A Pllt-.,. for aiiiVW'IIInct llllllu-nmDCI.aon

When !he hud moves closer to an obJect, the visUi I axes of !he e)'eS must movoe closer together (mnwrgence) and stmu/lzlni!OU~ the lenses must ildjust !heir foal lengdl (aa:ommodiltlon). Both processes ue necess;~ry for il sharp. thre.dlmenslonal VISUilllmpresslon. Three subproceses un be Identified In convergence and accommodation: 1. In CllllWI"gence.ltle two medial rectus muscles move the ocular afs inward to keep the imaQe of ltle approaching object on the fove;l centrillb. 2. In -mmoWtlon. thuurvature ofthe lms is inaused to keep the lmilge ofthe obfect shll rplyfoll!Sed on the rt41na. The lens Is flattened by contr..ction of the lenticular fibers, which are attached to thuiliary mll!lcle. When the clll.iry muscle contncts during accommodation, it relaxes the tension on the lenticular fibers, and the intrinsic pressure of ltle lens causes It to wume il more rounded shape. l. The fl'lpil is constricted by the 5Phincter pupillae to increase visual acuity. Convergence and accommodation miiiY be conscious (fbclng the gaze on a near obfect) or unconsdous (fixing the gaze on iln approaching illttDmoiJIIe). Most of the lDCDns of the ltllrd neuron In the Ylsuill piithway course In the optic nerve to the later~ geniculate body. There they m: relayed tD ltle fourth neuron, whasumns prufect to the primary vis~ cortex(aru17). ,_,, from the secondaryvisual aru (19) flnillly re;~ch

362

the prell!ctal area by way of synaptic INys and intarneurons. Anothet relily oc:Cllrs at that level, and the iiDCOns from tnese neurons llermlnilte In Pl!!rtl.a's nudeus, which Is loCilted blltWeetl the two Edlnger-westph;;ol nudeI(~ visani oculomotor nuclei). Two functionally distinct groups of na~rons ant located In l'lrll.i's nucleus: • For accommodation, one group of neurons relays impulses to the .somotornoiDr oculomomr nudeus, whose iiDCOns piSS directly to the medial rectus muscle. • The other group relays ltle neurons responsible for acmm modation and pupillary constriction to the ~(paruympathetic) accessory nudel of the oculomotor nerve (parasympathetic lnnerv~tion is illustrated here fw one side only). Afller synapsing ln this nuclear region, the preganglionic piirasympathetlc alUins pw tD the cdlary ganglion, where ltle central na~ron synapses with the perlphen~l pamympiithelic neuron. Again, two groups of neurons are dlstlngulshed: one pilsse!l to the clll.i ry muscle (i!Ccommodatlon) and the vther to the pupillary sphincller (pupillary consb1cUon). 11le pupillary sphlnctl!r light response Is abolished Intertiary syphilis, while accommodation (ciliary muscle) ilnd convergena: ant preserved. This phenomenon, called an Argyll Rtlbetson pupil. suggests that the connections tD the cllllry and fl'lplllary sphincter musdes are mediated by different tracts, although the anatomy«these tracts Is not¢ fully underrtoacl.

Neuruanatvmy -

12. FunctlonaiSysmns

-w.:: - - - - Pllplllory

sphlllc:b!r

-

Shlrtdlory

p.~-=----+---- 'YI...-.IQQIIam­

(fdnger-Watphal) nudet

I ~tmtu!.dan of puplll1ry 111111-the light rdu The pupillary llgllt rvllex enables tfle f!Ye ID illdapt to varying levels of

brightness. Whn1 a large 1mount of light entm: the ~.liR the beam of,. ftnhllght, the pupn constrtc:ts (txJ prot:Ktthe phol:on!ap!Drs In the retina); when the light fades. the pupil dil.ru. As the tenn "reflex• im-

plle:i, lflls adlptltlon takes place without conscious Input (nongWc1J/m part of the VIsual pathway).

Afhn·W'It limb Dfth•llght l1lfta: The first three neurons (first neurons: rodund cones; second neurons: bipolar cells: third neurons: ganglion cells) In theflll'errnt limb of the light reflex are lotated In the retina. The amns from the ganglion cells form the optic n~. The UDns responsible for the llghtl"lflex(llght blue) pw to the pretl!ctil area (nongenlculm p;1rtofthevisual pathW\Iy) in the medial rootoftheoptictrac:t. The other amns pillS txJ the literal genlculltle body (dark blue). AftEr synilpslng In the pretectal nudeus, the axons from lhe fourth neurons p;ISS txJ lfle paruymp;lthetk: nude! (aa:essory nude! of lfle oculomotxJr neM: Edinger-Westphal nuclei) of the oculomotor nerw. Because both sides illl' inn~. a c:onsmsucrllightresponse an OCOJr (see below). Elfwent limb Df the 11ght 1-.fta: The fifth neurons located In the Edlnger-Westphil nucleus (centnJJ parasympathetic neurons) dlstrfbull! their ;mons to the ciliary ganglion. There thry are ~ayed to the sixth neurons ~ p;~ruympath~c neurons). whose iliOIIS lflen pi!SS txJ the pu pdlary sphincter. The chct pupllliry Ught ll'Sponse Is distinguished fTwn the fndina re-

The dlrert l"ht respanse Is lli:Sted by COII'trlng both eyes of the mnsdous, cooperltlw pltlent and then uncowrtng one f!Ye. After 1 short Iaten~ period, lhe pupil of the light-ap~ed ~will mnmct. Toll!stthe lndhd:l..htrapo~We, the II!X.Imlner pl.ac:es his hind on the bridge of the patienrs nose, shading one eye from the beem of a flashlight while shining It fntxJ the oth~ eye. The object Is txJ test whelfler shining the light lntxJ one f!Ye will uuse lhe pupil of the shaded rye txJ contract as -n (coolliiJJSIXII light mponse). Loss ofthe l"ht respanse due txJ l:lltllln lesloi'IS: With a un llater.al optic nerve lesion, shining a light ll'ltxJ the afrectad side wtlllndua no direct light response on the affected side. The consensual light response on lhe opposite side will also be lost beause of Impairment ofthe ilh!rent limb of the light response on the afl'ec:ted side. lllumin~on of the INKI(fut2d side will. of c:ou rse, elicit pupdlary c:ontnctlon on that side (direct llg ht response). A consensual light respanse Is also present because lfle liferent signals for lflls reflex 1 re mediated by lfle unlffected side while lhe efferent signals an notmedllted by the optic nerve. Wllh illesion ofthe JNIOISympathetit oculomotor nudeus or ciliary ganglion, the efferart: limb ofthe reflex Is lort. In either case the pltlent has no direct or Indirect pupillary llgllt response on lhellfectecl side. A lesion of the optic radlitlon or ~I corWI (genlcultm! part of the visual pathway) does notibollsh this reftell.n ltwllllffectonlythe genial lite part ofthe vtsual plthMy.

sponse:

363

Neuroai'H1tomy - - 12. Functional S}tmms

12.20 Visual System: Coordination of Eye Movement

Rostrlllln!J!I'---7-f'------~

!tltlll nucleus of medial lonijltudnal t.udculus (rlMLF)

-....:~-4~~~~~-- Nudeusof

IIVC!lle.rnerw

~halic

retla.iar

- ----7.:=--- - -

-":-""'l::"~-r--::----

fcrmlllon (MRf)

MedlallangJ. tudnalfaos.d'cuha

(MLF)

P.ar.unedlan _ __::;,.,-- - - - pontine 1\'t!cullr

-

~lon(PPRf)

H -..,--,-- - - NUdMcf

ab6JCEnt nen.oe

..

A OculomQtornudel nd tfu:fr hlghcramncctlonJin tfu: br.llnstem a Mlds.ilgiUal section VIewed fi'om the left side. b ClraJlt diagram showing the supranuclear organization of eye mcM!ments. Wilen we shift our gaze to a new object. we s-Mftly move the as of 11ts!or1 of our eye~ t:owilrd the Intended t1rget. Theie rapid. precise. "ballistic" eye movements are called sat:aldes. They are preprogr.amrned and. once initiated. cannot bto alb!red until the C!lld of the Si!ICtadic roowment. The nudel of all tile nerves that supply the eye muscles (nuclei of cranial nerves Ill, IV, and VI, shaded red) .are ln~ved In tarry· lrlg out tilese mOYements. They are lntetmnnected for this pul)lose by tne mediollongitvdjntlf {osOcui~IS (sil;rded blue; sed kit its location}. BecauJe these comph:11. movemC!Ilts eJSentially ln~ve all of tile mra· ocular muscles and tne nerves supplyfr~g tnem. tne ac:tlvltyofthe nuclei must be coordlrlilted at a higher or supronudl!ar level. This means. for

364

aample, tilat ~en we g;sze to the right with the rlgltt eye. the right lateral rectus mil!de (CNVI. abducent nudeu~ activatEd) must contri!ICt whOe Ute right medial rectlJs musde (CN Ill, oculomotor nucleus lnhl~ ited) must relax. Fortne left eye. the left lateral rectlJs (CNVI) mllrt relax whne tne left medial rectus (CN Ill) must contract. Movements of this kind that ln~ve both eyes ire tailed COIIjugatl! ey1! movements. These movernentsare coordinated by several centers(premotor nuclei, shaded purple). Horizont11 gaze movemC!Ilts are programmed in the nuclear neglotl of the parimedlan pontine reticular fonmatlon (PPRf). while wrtlcal gaze ~ents ire prvgr.ammed In Ute rostral Interstitial nudew ofthe medlallongltudlr~al fasclculus (riMLF). Both gazecenlll!rs establish bi1ater~l c011nedians with tne nuclei of aanial nerves III.IV. and VI. The tonic slgr~als for malnt11nlng the new eye posldor1 originate from the nucleus preposltus hypoglossi (see ;a).

Co111a>- --.;..?-----:~!.'\, nudar film I

_AL:~---=--- Un!b...

'-

....,duct

\Jo-.!lb - - - - - - - Meclll langltudlnol folliculus

t:o111cospml -.....;;....--\ b'.a

4!,.-..:....-_..;..._ _ _ Nudeusaf abdl.ant""""'

I CouiH Gf tile medllllongltudl111l f..cta.~lusln the bl'llnstem MldAgltt.l J«tton viewed from the left side.

The medial longltlJdlnal f.udculus runs antzrior to the cerebral aqueduct on both sides and con1fnues from the mesencephalon to the cervical spinal cord. It tn nsmlts ftbers for the coordination of conjugate eye mCMments. A lesion of lfle MLF results In lntzrnuclear ophth.almoplegla (see C).

C ._lon of the mtdlallonglllldlnal faldcUUIII'IIflrltamudHrophth81· maples~II

-.....cl•

.........,h.ll

~­

ebd. . . . . . . . . .UI)

• Anlllnorvlew

Right

~

!

Medill A!c1la - - - . ; . . . . (not •
...

:

I

oa.iamallornerw - 1

I

Medii ----,~KJ langltudll'oll losdaJius

+~L---

Nudeusaf ca.iamatar nerw

4-;L----- Nudeusot tn>
The medlil longlllldlnal f.asclculus lntzrmnnects the oculonnot:Dt nuclei .and o~lso mnnects themwtdltbeopposlteslde(b). Whenthls"lnfunnillon lllg~ Is lnterrupted,lntennudar ophthalmoplegia develops. This type of lesion mOJt commonly ocaJts between the nudeus of the abd uc:ent nerve 1nd the owlomot:Dr nucleus. It may be unilateral or bilateril. Typical uuses ane multiple sclerosis and diminished blood flow. The lesion is manifested by the loss of conjugate eye movements (a). With i lesion ofthe left medlallongltlJdlnal f.Jsdculus, ill shown here. the left medial rectus muscle is no longer actlvll:ed during gaze to the rtgl'lt. The t)'l cannot be mowd lll~~«~rd on the side of the lesion (lou of the medial rectus), and the opposite t)'l goes Into an ibductlng nystilgmus (lateral rectus is lntlct and inneMted by the abducent nerve). R.eflex rT'IIMITients such as conwrgenat are not Impaired, as there Is no perlpheril or nuclear lesion and this re.Jctton Is not medlltlld by the medial longftudln.il faKic:uiUI.

365

NeurocrncrbJmy - - 12. Rlndfonal Sysmns

12.21 Auditory Pathway

I

~

'\.

;

~

~

. . . . . / uten~lsuiC11S )--" . ......._,_ Trai!M
•

r .,

...J.-.

ll!mporll gyrl

/ \

~

'"..."'

CDmmlosurerl ---..;"[ Infeft or col halII

Lmnl

~mniKu• ----JJ Posteffor

tWddofr.tu'al -

codllelr

-

nucleus

lomniKu•

:ZO,OIIO Hz (:ZO kHz)

_..-- CDdllear

~---duct • 4 - eortlorgan

Meclulary ------+tt+--,.r siJfoe

• "--lnnor holralll

NudiUiof t - I d body

A Alferentaudlblry pllfMqoftfw leftur The reaptors of the auditory pathway are the Inner hilr cells of the organ of Corti. Because they Jack neural processes, they are called ur:ondaty seuory ails. They are located in the cochll!.ar duct of the

basilar membrane ;md are studded with stereodlla, which are exposed tD sheiring forces from the tectort.if membr;me fn response IDa travel·

lng WM!. This causes bowing of the stereocilia (seep.. 151). These bow· ing m~menn Kt n a stimulus to~ c.aKadH of neural signals. Dendritic proceBeS of the bipolar neurons fn the spiral ganglion pick up the stlmu Ius. The bipolar neurons then transmit Impulses vta their axons, ~lch are colfectl!d to form the cochl.ear nerw, to the anter1or and posterior cochlear nuclei. In these nuclei the signals are relayed to the JeCOnd neuron of the audltoty pathway. lnfonmtlon from the cochlear nudel fs then transmitted vta ~ nudd to the ptfm;ary 11udftory cortex. ~ere the auditory Information Is consCiously J)I!IU!ved (iNiogous ID the visual cortl!!x). The primary auditory cortex is loatzd in the trans· verse temporal gyri (HeschIgyri. Brodman n ill"llll41). The auditory path· w.~y thus mntalns the following key stations:

366

• • • • • • • •

Inner hair cells in the organ of Corti Splralgangllon Anterior 11nd posterior cochleir nudel Nucleus ofthe trapezoid body and superior olivary nucleus Nucleus of the lateral lemniscus Inferior colllcular nucleus Nucleusofmedlillgenlculatl!body Primary auditory cortex In the tempora!lobe (transverse temporal gyri • Hesch! gyri or Bmd mann area 41)

The lndMdual p.1111J of the cochll!.a ane correlated with specific areas In the audito
Nf!uiOGDGtomy - - 12. f'undiomltiSymms

CDdlle<ar nucleus

Superior elM! wllll superlor cl tv.ary nudeus

8 Theltilpedluneflu: When !he volume of in acoustic signal re;aches a cert.11n lhreshold,lhe stapedius reflex triggers a contraction of the stapedfla muscle. Thh reflex c.1n be utilized to tut he
fadal nucltus

kes the stapedius reflex ;md the tympanic mernbr;me stiffens. The change In !he resistance of the tympanic mernbr;me Is !hen mei!ISured .md recorded. The aflierent trmb of !his reflex Is In the cochlear nerve. Information is co~d to the facial nucleus on each side byway of the superior olhr.sry nucleus. The f(ffmlt limb of this reflex Is formed by special visceromotor fibers of!he facial nerve.

Inner hair all

Liltler.ol cllllccodllea r bundle

' .i -----I

c Efferent Abers from the olhe till the Corti org~~n Besides tile ilfferentflbers from the organ of Corti (see A. shown here In blue), which form !he vestlbulocochlear nerve, !hen ire also efferent fibers (red) that pass to !he organ of Corti In !he lnntf ear and are conarnedwith the active preprocessing ofsound (•axhlearamplifier"}and acoustic protection. The efferent fibers arise from neurons thit are to· t.'!ted lr1 elttterthe lateral or medial part of!he superforoiiYe ind project &om there to the cochlea (lateral or medial otrvocochlear bundle). The

ltl,lf,

fibers of !he lateral neuron$ p;~~s uncros.ml to the dendrites of the irtnu hair cells, whlle the flbers of the medial neuron$ cross to the opposite side ind terminate at!he bise of!he ouf1!r hair cells, wflose actl¥1ty they Influence. When stlmulated,lhe outefhalrc4!11s c.1n ;u:ttvely amplify the traveling w.ave. This increases the sensitivity of !he inner hair cells (the actual receptor cells). The activity of the efferaru from the olive can be recorded as otoacoustlc emissiOn$ (OAE). This ll!St can be used to saeen for hearing abnormalities 11'1 newborns.

367

12.22 Vestibular System

,.

VE!il--- --1-- - Nud...d trachletr nerw 1.\ldnllll fudwha

NudiiUSd lbWant:MM!

~b""

t~ntllcn

- - - - --ff----....

__, ,. Utllde

To amcal mid

A cennl connectiON olthe WS11bul•rnerw Three systEms are lrwolved In the reguldlon of human balance: • Vestlbulu systEm • PrapriDCeptiVI! sysmm • VlsUil system The litter two systems h- alre.~dy bHn described. The perlpher;ll receptors of the wstfblllarlfSCim 1re loab!d In the membr.mous labyrinth (see petrGuJ bone, pp. 1<10, 152), which consists of the utricle and saccule and the ampu IIH of the three semlclrOJiiu ducts. The mac:ulile of the utride and saccule respond to linear acceleration, while the semicircular duct Orgins In the ampullllry crests respond to angular (rotitlonal) ac:cele~on. Lib the hair cells of the Inner ear. the reCRptors of the vatibular sptl!m are ~sensory ails. The basal portions of

368

-the secondary sensory cells are surrounded by dendfrtic processes of bi· polar neurons. Their perlluirya are loab!d In the vestibular ganglion. The axons fram these neurons fllnn the wsttbula r nerve and tll!!rmlnate In the four vestlbulllr nuc:lel (see C). Besides input from the 'iatibular apparidus, these nuc:lelalso rec:elw sensory In put (seel). The llleStlbular nuclei sh- a topographiCal organization (seeC} and distribute their efferent fibers to three targets: • MoiDr neurons In the spinal cord via the lateralllleStlbulosplnal tract. These motor neurons help to maintain upright stance, mainly by lncre.~sing the tone
Nf!uiOGDGtomy - - 12. f'undiomliiSymms

Hypo-

Thalamus

thalamus

8 Centrill role of the vestibular nudelln the matntenilnce ofballnCit The ~nt fibt'rs tmt p;us tD the vestibular nudC!i and the eff~nt

r.-

bers that emerge from them demonstrate the central role of lflese nuclei In maintaining balance. The vestibular nuclei recefwoe afferent Input frcmthevestlbular system, proprlocepawoe system (posltlol\ ~. muscles, and joints), and viswl ~m. They then distribute dferent fibt'rs to nuclellflat controllfle motor systems Important for balance. These nuclei are located In the: • Spinal cord (motor support), • Cerebellum (ffne control of motor funcUon}, and • Br<~insb!m (oculomotor nuclei for oculomomrfunction). Efti!rents from the vestlbular nude!" are also dlstrtbutl!d tD the following re-gions:

Spinal cord

• Thalamus and cottn (spatial sense) • Hypothalamus (autonomic regulill!on: vomiting In mponsetovertlgo) Nob!; Acute fillune of the Yeitlbular system Is manfuted by rotary wrtlgo.

&------:::~--

Nudtwof

oalomo!D"ner-Ye

C Vesttbulnnudel: topogr;lphlc Ol'jilnlutton and cent.r.ll

connec:Uons Four nuclei are distinguished: • • • •

Superiorvestibular nLJCieus (ofBechten!w} Literal vestibular nucleus (ofDeltm) Medial wstlbular nucleus (of Schwalbe) lnti!rforvestlbularnucleus (ofRDIIer)

The wstlbular system has a topographic organlz:atlon: • The afferent flben of the saccular macula terminate In the Inferior vestlbular nucleus and lateral wstlbular nucleus. • The afferent fibers of the utricular marula termina!J! in the medial part of lfle lnfafor venlbular nucleus, the lateral part of lfle medial vestibular nucleus. and the lal:efal vestibular nucleus.

• The afferent fibers from the ampullary crests of the semlclraJiar canals tennlnate In the superforvestlbular nucleus, the upper part of the infC!riorvestibular nucleus, and the lateral veJtibular nucleus. The efferent fibers from the lateral vestibular nudeus pass tD the lateral vest!bulo!plnal tr.1rt. This lr.lct extends to the sacral part of the spinal cord, Its axons terminating on motllr neurons. Functionally It Is conCitmed wth lleeplng the body uprfght, chiefly by Increasing the tone of the extensar musdes. Thelll!stibulaa!rebellarfibers fnlm the other three nuclei
369

Neuroai'H1tomy - - 12. Functional S}tmms

12.23 Gustatory System (Taste)

Medii Pin' bllldial nutllui

~~::,..,.'--'---':-7'----

A Gusbtory pillthw.ly Tbe receptors for !he sense of taste .ill'e the wte buds of the tongue (see 8). Unlike other reCI!ptor cells, the receptDr ails of the taste buds are speclallz:ed epithelial cells (secondary sensory CElls. as they do not have an a110n). When these epithelial cells are chemically stimulated, the base of the cells release.sglut.1mate, 'Which stimulates!he pertpher.ill protl!sses of affi!tef'lt cranial nerves. These diffi!rent cranial nerves serve dlffenmt areas of the toogue. It Is rare, thErefore, for a complete loss of t3ste (ageusia) tD occur. • Tbeontrrlorttlr!Hftlrdsofthetoogue are supplied bythefadal nerve (CN VII), the .ilfferent fibers first passing In the lingu..l nerve (br.ilnch of the trigeminal nerve) and thl!n in the dlorda tympani to the genic· ulate ganglion of the facial nerve. • Tbe pomdor third of the tongue and !he val/are poplll« are supplied by the glossopharyngeal nerve (Oil IX). • Tbe I!Pfglctt1s Is supplied by !he vagus nerve (CN X). Perlphml processes ftom pse~.~dounlpolar gangllon cells (~Jch correspond to p.seudounipolar spinal ganglion cells) terminate on the taste bucb. The centtal portions of these processes convey t3ste lnforma· tlon tD!he gustatory part of the n~Kieus of!he sollt.1rytract. Thus. they function as the first affi!rent neuron of the gllrtatory patilway. Their

370

Splnalnudeusof !Jfgemtnalnerw

perikarya are located In !he geniculate ganglion for the f.rclal nerw. In the Jnli!rtor (pe1rosaQ ganglion for the glossopharyngeal nerve• .ilnd In the inferior {nodose) ganglion far the vagus nerve. Aftlr synapsing in the gustatory part of the nucleus of the sallt.1ry tract. the allOns ftom the second neuron are believed to terminate In the medial parabrachlal nucleus. 'Where they are relayed to the third ne~.~ron. Most d the ax.ons fram the third neuran aoss tD the appDSite side and pass in the dorsal trlgemlnothalamlc tract tD the contralateral ventral posteromedial nucleus of the thalamus. Some of the axons travel unaossed In the same structures. The fourth neurons of the gust.iltorypathway.loc.ttled In the thalamU'I. project to the PQJtcentralgyrus and insular cortex. where the fifth neuron Is located. Col laterals from the first and second ne~.~rans of the gustatory afferent pathway are distributed tD the superior and lnti!rtor salllliltory nuclei. Afferent flnpulses In these tlben Induce !he secretion of uliv~ during t'ating ("s~lillilry n!flex•). The p~r~symp;athl!tic preganglionic fibers exit the bralnstan viii cranial nerves VII and IX (see the desafptlons of these cranial nerves for detalls). Besides this pcJrely gust;rtory pathway, spicy foods may also stimulate trigeminal fibers (nat shown). which cantribute to the sensation of l:asb!. Finally. alfac· tion(thesenseofsmell).mo.lsa majorcomponentafthesenseoftaste as It Is subjectively pen:el~: patients who annot smell (anosmosla) report that their food tastes .ilbnarmally bland.

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

b

f"ollite paplllae{d)

>----- FU'Igllorm

papll;~e(c)

' B Organlutfon ofdie tillite I"'!Upf:Drs tn die tDngue

The human tongue «~nt.llns ~pproxlmately 4600 taste buds In whkh ttle secondary sensory cells for taste perception are collected. The tnte buds (see C) ire embedded In the epithelium of the llnguil m~Kosa ind are loc.tted on !he $Urf.ace expansions ofUie llngwl m~Ja~Sa-Uie val· lirte p;1plilae (prfndpal slte, b), the fungifvnn papillae(,), and thefoliatt> p;~plllae (d). Addltfonally,lsolilted taste buds are locited In the m~Kow membranes or the soft p;~lm and pharynx. The sumoundlng serous

glands of the tongue (Ellner glands),lM'IIch are most dosely .iS$0Ciated with the vallatz p;apnliiiC\. connantly w.ah the tastt> buds clean to allow for new tasting. Humans Cin perce!Ye five bisslc taste q~aalltfes: sweet, $OUr, salty. bitter. and a flfth •savory" qwllty, called umaml, which Is activated by glutamatz {a tiLrtt! enhancer).

Ught

b151etll!ll

C M'roscopfutructure of ;a tillte bud Nerves Induce the formalfon or taste buds In Ule oral mucosa. Ax.ons of cranial nel'lll!!s VII, IX. and Xgrow into !he oral mucosa from the basal slde and Induce the epithelium to dlfferentlilte lnbl the light and dark taste cells(= mod11!ed eptthdlal cells). Both types of taste cell have mlcrOYllll that extend to the gustatory pore. FGr $OUr ind $alty, the taste cell is stimulated by hydrogen ions and other cations. The othet" taste q~aalltfes are mediated by receptor proteins to which the liM-molecularweight flavored subst.lnces bind {details may be found In textbooks of physiology). When !he low-molewlar-welght flavored substances bind to the receptor proteins, they induce signal transduction ttlat causes the release of glut
Ba1.11ull

tam!ull

371

Neurot~I'H1tomy - -

12. Functional S}tmms

12.24 Olfactory System (Smell)

Longltudnalstl'lle

lntl!!l>edu naln

nuc:!Ns

Medl~l O~(b)ly

Hilbl!nular

nuclei

stria Tegrnerul nuc:!Ns

O~(b)ly

bulb ~wl!h

Olfltcb)ry flbe-s

•

~~~

b
Olliu:blry

mucosa

-

i'replrifonn

A Olflrc:tory system: tfle olfactory m-a and Its Ol!lltral conntctt:ons

Olfactory tract viewed In mlds;rgltt
betfle prfrnaryolfact:orycoruxln the strk:tsense.lt contains tfletfllrd neurons ofthe olf.-actory pathway. Nob!: The p~lrlflltm are:~ Is shaded In b, ~ng at lfle {unction of the balo!l side of the frontal lobe and the medial side of t!tetempc~ral lobe. • OlfleralUlns of tire olfactory tract run lntflemedlalofKtorylltlfatD nuclei In the septal (subc.-allosaO .-area. which Is part ofthe limbic system (seep. 374),
372

Dligonal stri1

Anteior()t!rfilmed sub:stint
Nob!: None ofthese three tracts ;rre routed throcJgh the thalamus. Thus. the olfactory system Is the only sensory system that Is not relayed In the thalamus befane reachirlg lfle col'lzx. There is. however. an indirect route from the primary olf;rct:ory cortex to the neocorte11. passing throcJg the thalamus ind terminating In the ba1al forebrain. The olt.rctoryslgnals aretiJrtfler analy.wl In these bas.al portlonsoftheforebr.-aln (Mtshown). The olf.lcblry symm Is llnklld to other brain ;rreas well beyond the primary olfact:ory cortlc:al
• Hypothalamk nuclei • RetJCIJlar formation • Sillvatory nude! • Donal vagal nucleus The .axons !hat run In the medullary striae of the thalamus terminate In the ~benul~r nuclei. This tract also continues to tfle briinstem. wnere ltstlmulatessallwlion In response to smell.

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

---Ccn~

tlaue

,_..,imr'-ini:-.-r-m-ir:if-- Oibrlfonn

"'~ D;ulccells

Bowman gland

•

c

8 Off\H;blry mUCOM a vomcror..~l 01'911'1 (VNO) The olfadory miiCDS.) ocaJples an area of approximately 2 cm2 on the

roof of each nas.1l ca\llty, and 101 primary sensory cells a reconcentrated in each of these areas (a). /It the malecular lew!, the alfactory recepmr protelnsarelocatedlnthedllaofthe scmorycells(b). Each sensory cell has only one spedilllzed receptor protein that medlaw signal tr.lnsducUon 1/lben an odorant molecule binds to 1t Although humans are micr0$matit. h
C SynapUc p;IUI!ms tn m olfac:IXIry bulb

"'--~~--Per!·

glomerular cells

Spedallzed neurons 11'1 the olfactoJY bulb, called mitral cells, fonm aplcal dendrites that receive synaptit contact from the aXQIU of thous.1nds of primary sensory cdls. The dendrlre plus the synapsu make up the olfrsc· tory glomeruli. AKons from sensary ~Is wlth the s.1me receptor protein fonn glomeruli With only one or a small numberofmltral cells. The basal axons of the mitral cells fomn the olfactory tract. The amos that run ln the olf.-actorytJact project pr1m.-ar11yto the olf.-actory cortex but .-are also dlstnbuted 1» other nuclei In Ute CNS. The axon collatl!rals of tile mitral cells pass 1» gr.anule cells: both gr~nule c.ells and periglomenJiar cells Inhibit the activity of the mitral cells, causing less sensory Information to re;rch higher centers. These Inhibitory processes are believed to heighten olfactory contrast. which alds In Ute more .accurate perception of smells. The tuftl!!d ~Is, which also pnoject to the primary olfactJ:wy cortex. ;rre not shclwn.

Olt.u:tayflbeB

373

Neuroai'H1tomy - - 12. Functional S}tmms

12.25 Limbic System

......-----,-=-...,...:::........:___:~---

Ongulate gyrus

Subcalosal -~-..::....----+--.. .;area

AnUI'Ior-~~:_,_~=-----=::::=~~ Olmmlml~

Par.~alliu:!lxy

--....:...,,..-.....,.....,...-----"--

aru

Mamrnllary body

A Umblf system 'lltewed through the partSIIIytranlpel'l!nt CIII11!X Medi~l

view of tne right hemisph~. The term •limbic symm• (latin lfmbus- "border" or"frfnge•)w.lSftrstused by Broca In 1878.~collec­ tively desafbed tne gyrt surrounding the corpus e<~llosum. diencephalon. and bot~ a! ganglia as tne grand lobt nmblqut. The limbic symm encompaJ$n neo·, ~rthl· ~nd paleocortfe<~l reglom ~swell ~s subcortle<~l nuclei. The anatomic:<~! extent of tne llmbk system Is such that It e<~n exchange and lntegr.tte lnfonnatlon between the telencephalon (cerebral CDrtex), diencephalon, and mesencephalon. Viewed from the medial ~spectof the ce~bral hemispheres, tne limbic system Is seen to consist of an Inner arc and an outer arc. The outer arc Is fonned by: • hrahlppoe<~mpal gyrus, • Ongulate gyrus (also e<~lled the limbic gyrus), • SubCllllosal.il~il (para olfactory .il~a). and • Indusium griseum.

The inner arc is formed by: •

Hlppoe<~mpalformatlon.

• Fornix, • Sept<~ I area (also known simply as the septum),

• Diagonal bandofBroe<~ (not visible lnthlsW!w), and • P.ilmermrnal gyrus. The Umble system <1lso lnduc:le.s the amygdalae arid m<~mmlllary bodies. The following nuclei are also considered part of the limbic systzm but ~re notshclwn: the anterior thilamlc nucleus. habenular nucleus. dorsal tegmentill nudeus. <~nd lntefl>edunculilr nudws. The limbic system Is concerned with lhe regulation of drllle and .ilffec· tive behavior arid plays a aucial role in memory and reaming. The numben In lhe diagram lndlcatelhe Brvdmanr1 ~ms.

B Neuro111l draft (Pipez drallt) View of tne medial surf.ace of the right hemisphen!. Several nuclei of the Umble sy3tem are Jntercor~nected by a nfMOilal drc:u/t (see below) called the hpez circuit after the anatomist who first desclfbed It The sequence below lndlcatl!s the nuclei' (normal print) and tracts (llllfk print) that are the sucassive stations of this neuronal circuit:

Hippocampus- fomix- mammillary body- momml11mhalamfe 110ct (ViaJ o'Azyr bundle) - ~ntl!rior th~l;amic nuclei - tholtztnodngulo tract (rodlatJoo)- clngulate gyrus- dngu/olllppoa1tnp ffb«s- hlp~ campus.

~

thililmk nuclei

This neuronal drt1.1lt ln!l!rconr~ects ontogenle<~lly dlstfnct parts of the Umble system. It establishes a connect1or1 between lnfonnatlorl stored in the unconKious ~rid conscious behi!llior. Fomlx

374

Neuruanatvmy -

c

Cho..,.d pleow

12. FunctlonaiSysmns

~rchn.ctlnaftheNppomm.,.l

fvnn.tlon (after Bihr and FrotKher) VIewfrom antMlor left:. Nok: Th~ hippoampal ~lion hi!J 1 thl'ft-

layered allooorte:k Instead af 1 six-layered lsocortD(Iowerleftlndl~).ltlu phylogenttlc:.~lly older structure th.-.n the lsocorttx. At the c:enmrofthe allocortD Is 1 bind of neurons that

Dlf'llilly

podood rwurons

o.rnm-- gyrus

Ternparol ham

l'llllhlppo- _ __,;:GI......I

- - - Collterll emInonce

~

Enll:ortllnol a11tu

neuronaii.J)'f!f' of the hippocampus (- hlppoampw proper ·Ammon's horn). The nM.Jrons In this layer are mainly pynmlcbl cells. Thl'ft regionJ, desig!'lilted CA 1-
l'anlx

,...-----l'ylllmklol ads lt!mparol ham

p,.... oublculum

ArN21 ----':-~_.

(on!Drlllnol ~on)

D Connectlont af the hlJ)poc:MIIpUI Left antmor view. The most Important~­ ent pathway tD the hippocampus Is the ~t path (blue), which mends from the entorhlnal region (triangular pyramidal cells of Brodmann ars 21) tD the hippocampus (where It Cllds tn 1 synapse). The neurons that project from aru 28 Into the hlppoc:ampus rec:tlYe afferent input from many brain regions. Thus, the entorhln~l region Is considered the gatew.ay to the hippocampus. The pyramidal alls of Ammon's hom (triangles) send their oons Into the fombc, and the nons transmitted via the fomlx continue to the rn~mmlllary body (PapH neuronal drc:ult) or tD the Mptal nudel.

E lmporbnl: definitions perbfniiiQ ta the limbic syslilm Ardllcorta

Hlppac:ilmpus(..a-nmr-r.l)

Umbk.,.._. 1mportant coordinating IY'tem for mtmory and emotions. Indudes the foJJD'tYing l!lenaphcrllcstructum: clngulltl gyrus, parahlppoc~mpal gyrus, hlppaampo~l fonnlllion, ..ptll nud1l, and anwdala. Its p1ra11c a1111ponents Indude lhe ant.rlor thalamic nucleus. mam miliary

Ammon's horn (hlppoc~mpus prope!'), clenmte gyrus (clentite fasc:ll). sublwlum (some authors conslcl•r It part ofthe hlppoampal formation r;olher than the hippocampus lbllf)

porMII:S a.- the raphe nuclei. Th1 m1dilll forabrain bundle and the dorsal l...glludlnal h..:lculus lllntrlbut. to the flblr tracts afthe lim blc !Y'tem.

Phylogenetlally old structures af the ar8>111l Cllrtec: does not"-

• slx~.yered 1 rc:hiiKtuiW

.-.c.

bodies, nudeus io:umbcns, and h1ba1ullr nudeus. Its bratlutlm
Perlerd!brta A braad tramltlanal mne II'CIUnd .... hlppocampuo. aomlsllng af the dnguiD gyrus, the 1lthmusaftlw dngullla and the para~

wuo.

Cilmpil gyrus

375

Neuroai'H1tomy - - 12. Functional S}tmms

12.26 Brain: Fiber Tracts

A Flbertr.lctl Abef tracts ~re tne "Information highways• of the whib! matter of tne brain and spinal cord. The most Important wnns pat;rlnlng to CNS fiber tracts are listed In the table.

Connect the urebr.al mrtu liD subcurtk.al c:enll!rs, either .ascending or descending Connectsubcartlal centers to the ~ral mrtex Connect the urebr.al-to deeperunte~ Connect diffi!rent CMical a,_ within one hemisphere Connect blot cortlal areuln both hemlspha-es (-lnterllemlspherfc association fibers)

Special projection tract~ the limbic symm

t.IIJkiS -~.:...:=---"':'------

c:allc&sum

Cen!bral peduncle

B Brain specTmen prep.~ red tD show tfu~ stnJc:ture oltfle PI'OiectiDIIf!'bell

Medlalvlew of the right hemisphere. This type of specimen Is prepared byfixing the briln lnform~ldehyde ind then freezing ft. The gray m..u:er. which hillS a high w.mr content, 1~ destroyed by h:e-crystil formatfoD, while the lipid-conuining whitt' matter rem;ains reliltivc!ly inuct. The frozen brain Is then lhiwed, .1nd the tissue Is dissected and teased with a spiltul~ to bring out tne ftbef irthltecture of the white matter. The fiber~ represent bundled -~tNt p;1" collecttlle!y frcm thel'r site of

origination to their destination. Beause the brain hn a topographic

376

org~nlza!Son. m~nyequldlrectlonal axons pass through thewhlte m..u:er as fasciculi (for the designations of different fiber types. see A. above}. The projection fibers shclwn hEre connect the cerebral cortex to subcortltil structures (e.g .. bisal g~nglla. spinal cord). A distinction Is drawn be~ ascending and descending flbefs ~nd thel'r systems. In desc.ending systems, the cell bodiesofthe neurons are locab!!d ir1the~ rebril cortex. and their amns terminate In subcortical structures (e.g .• the COI1kosplnal trilct).ln ascending systems. the naJrons from subcortltil structures terminate In the cerebral cortex (e.g .• sensory tr.acts from the spinal cord).

OrtJIIdrontol fndallus

~prar acdpllll·

Conbrll II'Clllllt

fRWibllfalc:fcuh•

ftbo11

•

lnfe1orocc~

Uncln~

fronbol t..dculus

fadculus

C~nllbcn

a l.atlnl vtew of tne left hemisphere. II Anterfor vtew of the right hemisphere. c Anll!r1or view of shorhssociiUon ftbers. Lang association fibers lntercon nect different brain areas that are located In different Job~. whereas short assodiltlon flben lnterc:XInnect

commllwN!

For«ps

cortical areas within the same lobe. Adjacent cortical areas are lnte~"C:Cm­ nected by short. IJ-shaped aroute ftbers, which run just below the cortex.

CXJmmlssure

-----,,.--~,...--'f"T

minor

D CammiHul'ill flbl!n • Medii I VIew of tne right hemlsphen!. It Su per1or vtew of the transparent brain. Commlssunl fibers Interconnect the two hemispheres of the br;lln. The most lmpor13nt connKtlng structure between tne hemispheres Is the corpus nllasum. If the cospus allosum Is Intentionally divided, as In a neurosurgical procedure., the two halves oftne brain can no longer CDm· munlcate with each Olher ("spllt-bratn• piltlent. see p.l80). There are other, smaller mmmlssunl tracts besides the corpus c;allosum (ilnll!rtor commissure, fomk.al CDmml!.sure).

E Sonwtutuplc 1111Pnlutlan aldie lllbrn1l aplde Transverse section. Both ascending and d~UCM~ding projection fibers pass through the Internal capsule. If blood flow to the lntern;al upsule Is Interrupted, ill by a stro!Ge. these ucendlng and descending tracts undergo lmM!rslble diiiNige. The llgure of the child shows how the sites where tne pyramidal tract fibers pass through tne internal capsule can be assigned to peripheral areas of tne human body. Thus. we see that SINIIIer lesions of tne Internal capsule ml)' cause ;a loss of central Innervation (• spastic paralysis) In certain ueas of tne body. This accounts for the great £finical impor13nce of this structure. The internal capsule Is bounded medially by the thalamus and the head of the caudate nudeus. and lilterally by the globus p1llldus and putamen. The Internal capsule CDnststs of an anterior limb, 1 genu, and a posterior limb. which are tr~ by sp~cific tracts: Anb!rior limb

• Frontopontine tracts (red dashes) • Anterior thollllmlc pedu nde (blue diShes)

Cierlu of internal capsule • CorUmnudear fibers (red dots) Posterior limb

• Cortlmspln.al tlben (red dots) • Post~rior th.alamic p~d uncle (blue dots) • Temporopont!netnct(orange dots) • Posterior th;al.amlc peduncle (light blue dots)

377

Neuroai'H1tomy - - 12. Functional S}tmms

12.27 Brain: Functional Organization

O!ntr.ll JUIC\11

Asso dlltlcn c:ortl!x

~ (Brodmannlft1117) Mma~----~~~~~--~------~

mctor cortex

-

>----~r-~~-- Pl'm1ry

JOrnaticolensary

-

Seolndary -----'.ii--""===;~-~-a~dllory

A FuncUon;~l OI'IJilllllz.1Uon ofthe~ I.J!ft lilterillllfew. The p!1mary sensory ~nd motor are.u are shown ll'lred, and the ~ms of the issodatfon cortex ire shown In different shades of green. Projtctlol'lt:racts begin orend.respectlvdy.ln the pdmary motor or sensory areas. More INn 80'.1; of the cortical surface .area Is association cortex. which is st
which 1\as lncrtilsed grtiltfy Ins~ -the course of human ewlutlon. The functional organizatian patta!rn shewn hen!, such as the localization of the pdmary motor cortex In the precentr.ll gyrms. c.1n be demonstrated In tilling subjects with modern Imaging techniques. The results ofsuch studies are Illustrated lnUieflgure.s below. Interestingly. the cortelations described in tllese studies Com!spond reasonablywell with the conical areas defined by Brodmann.

HIJlho:rlhin ----:-....::-:-=-::.......... M!l'1llje

blood flow

'-rtNn ----..:..:~

•

olM!I'
I Anal,stJ of bl';lln fwldfon bued on lb.Jdt• of regtonal cel't!br'lll blood flow

I.J!ftlatet'illllfewofthebr.arn. Whenneu~sareacttl/atedtheoyconsume more gluCOR and r;axygen. which mU$t be delivered w tllem via tile bloodstream. This may produce a detectible Increase 11'1 regional blood flow. These brilln maps Illustrate t1te local p;lttJ!ms of cerebral blood flow ~t re.st (a) and during mOYement of the right !\and (b). When the

378

right hand Is moved,lncreasedbloodflowls recorded In tile leftprecentill gyrus. which contains the motor representation of the right hand (see matDr hamuncuiU$ In 8 an p. 339). Slmult.lneous actlv.atlon Is noted in the sensory cortex of the pastantral negian, showing that the sensory cortex b also active during motor function (feedbi!dc loop).

Neui"Dttlllllamy - - 12. FunctlonaiSystmts

Mole

C Sad"'-'cftln DIUI'IINII proceullltl

(aftll!rStoppe. Hentxhel, and Munz) Patterns of brain acdvlty can also be demonrtr.Jted by functional magnetic resonance Imaging (IMRJ) .This prcllllden noninvasive method for lll\'eStlgatlng the metabolic activity oftne brain. Because no human brain Is Identical to any other, a comp.~r1son of several brains wlll show slight varlitlons In the dbb1btltlon of spedflc funcdons. By superimposing the results of ua minatlons In different brains, we can produce a

generalized maptnatshows tne approxlmabe distribution of brain functions. Comp.~re the summalkln map for female b!"lllru on the left with a map for male brains on the right. Both groups of subjects were given phonologlca I tasks based on recognizing differences In the meaning of spoken sounds. While the female subjects .acdvated botn sides of their brain v.flen soMng the tasks, the male subjects actlv.lted only the left side (the secdonallmages are viewed from below).

D MIHful•llng sullc:orual Cltftbln The ceneb~l cortex. the seat af our conscious thoughts and actions, Is lnftuenced by v.artous subcortical tel'lt2rs. The parts of the Umble system tNt are cruc~l for learning and memory are lndkabed ln light red.

379

12.28 Brain: Hemispheric Dominance

.......,.,... A Demollltl'allon rJf heml..,..ertc domlnlllte lor IJnguage 111 split. bn~ln pltlera (lfter ICilnkt. P1pe.1nd SllberNgl)

The corpus allosum Is by f1r the most lmportillnt commlssur1l tr<~ct. inten:onnecting areas of liklt function in bDih hanispheres f1f the briin. Bea use lesions of the c01pus allosum were once considered to h~W no cliniCill effects, sui'IJical dfvision of tfle c01pus callosum was commonly performed It one time In epileptic pill:lents to kltep epileptic seizures from spreading KrOSs the brain. This oper:iltfon IntErrupts the connections in the !tppef~ while leiiVing intact tfle more deeplysituill:ed dlfnaplxl/on, which contllns the optic tro~ct. Pill:lents who have undergone this operilltlon 1re tilled •spirt-brain patients.• They hOM! no obvious dlnlcal1bnormalltles, but spedal neuropsychologlc31 tests relleill deftclts, the study of which his lmpnMICI our understanding of brain function. In one bat the patient sits In front tA a screen on whh:h

380

words are proj«Ud. Meanwhile, the Pllient can grasp objects behind 1he screen wltflout being able to see them. When the word "Billl' Is flashed briefly on the left side of the screen, the p:iltfent pera!IYes It In 1he viJUII cortex on the right side (the opticIRI:t his not been cut). lieawe liingu<~ge production resides In the left hemisphere In 97111 of the population, the patient c:an not veri>alize tfle projected word out loud beause communlc:iltfon between the hemispheres has been Interrupted Itthe level ofthe tMnaph1lon (seltofspeech production). But 1he pltient is still• ble to feel the INII m1 nua lly and pick itout from other objects. The funcUon of the corpus allosum Is to enable both hemlsphe1'6 (which tin function Independently to <1 degree) to communiate with each other when the need arises. llec:iiuse of the phenomenon of hemispheric domiNnce, the corpus allosum In humans Is more elaborately developed than In other a nlmal species.

I HeailpheJtc: ~ry (ilfter Kllnkund Snbemlgl) SupertorW!w of the ttmporallobe fllll brain thz hlls been bien ;atyrt (I.e•• the fnmtallobes 1Mw been removed) along the ~I ftmlre. The planum limp~ loated on the posterior 01nd suplfior su ~face of the emporallobe, has different mniDurs on the two sides of the brain, b~

lng more pronounad on the left side than on the right In ~thirds of Individuals. The funcaonill slgnlnance of this iiSymmetry Is unartilln. ~ annGt explain it Jimply by noting thllt ~micke's speech ~re• iJ loated In thz part of the temporal lobe, beause while temporaluymmetry is present in only 671> of the population, die speech area is loated on die left side In 97%.

Mouth ond IDngue (mcrbr cur1D)

Suptrior long). bldlnal fasdallu.

-!:,----..;..:.-- Vllull

1uodollan a:Mta

Broca's area

c LII'IQ.,...e I !'HI In the nol'llllllydoml111nt left hensphere Lillri!ra I view. The brain contains severa I language arHS whose loss Is a~atedwith typical clinical symptgms. Wfmi~'sCIIN (the posterior part of area 22) Is necesMry for language comprehension, while Sroctr's am~ (arm 44) Is mncaned with language producaon. The two arms are

interronnected by the superior longitudina I(arcuate) mcku Ius. Broe<~'s area acttvms the mouth and tongue nglon of the motor mrtEx for ~ ;artkulation of Jflrrdl. The angular gyrus coordinates the in puts from the vfsllill, acoustic. and sorTYtDsensory cortices and relays them onWoilnl to Wernicke's ana.

381

12.29 Brain: Clinical Findings

The ligu~s in this unit illllltr* the correlitians tNt hlw been dis«Mred betweenspeclflc br•ln ~-and dnlalftndlngs. Sb.Jdles afthls lclndhiw en<~bledus to link ~ulu ~s Dfbehlvlcr, some illbnor-

mal, 1nd p.~rtlc:ul•r chnlm symptoms to spedflc 4lreiS In the bnin.

..

• c

A Nan•nnomyofemotl- (•ftcrBn.us) • libnllllew af the left hemisphere. II Anterior view af i CDnlllil sectlan thraugh the amygdala. c Mldugrttal S«tfon of the rfght hemlsp~. medial aspect. Emotion Is llnlaed tD spetlftc regions ofthe brain. The--.tromedlil prt>froonUI cortex is connected primanly to the amygdaloid bodis and is

bellewd to modulm emllllan, whlle the dorsaliltenll pmrontlll cartex Is connec:tl!d prtmarllyto the hlppaampus. This Is the~• af the cortex In which memorfes •re stDred <~long with their emotfo~YIIIillence. Abnonnalltles Gftflls networil ~bell~ to pl.y i role In depression.

8 Spread ofAlzNhllr"l dii!IIM thnJUQh 1M linin (aftw Bruk and Bruk) Medial vlewafth1 rlghthemlsphlre. Alzhelme!'s cllseue Is a relentlessly progrusiw disease Df the cerebral cortax tNt taLSes memory loss and, ftentually, profound dementli. The progression af the disease can be

• St3ges III-IV: the lesions hlv. spread tD Involve the limbic system (also part gf the allacarm!), tnd Initial clinic•l symptoms appear. These stages may be detectable by lm~glng studies In some cmes. • Sbges V-VI: the entire isOCCII'tu is iiMIMd, and the dinical rna nifestatlons are fully dewlaped.

demonstril2d -Mth special staining methods ilnd can be dMded Into ~a using the cl;,ssiflation of llr.lak and Braak: • Staga I-ll; the apiJ"rance of the nerve cells is ;~l~d in the periphery of the entorhlnal cort6 (• nnsentorhlnal region), which Is considered part of the <~llocorii!X (1M p.204). These mges ne still asymptgmatlc.

382

Thus, the oJIIocormt Is lmpartant In brain pithophyslology as the site of origin ofAlzheimer's demenU<~, - n though It makes up only 5:1 ofthe cerebro1l carWol-

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

C Mill chartges In the hlppoc:ilmpus tn ;a patTent wtth AlzheTJner•s dementTa Ce~mparing the br;in e~f a heefthy sub;ect (•) ~h that of a patient with Alzheimer's demenua (b), we nolfce that the lattef shows atrophy of the hippocampus. a brain region that is p.art of the al~rtex. We nCitlce. too, that the laterill vartrldes .-.re enl.-.rged lr1 the patient wth Alzheimer demen!Sa (from D. F. Bra us: fin Brdc ins G61im. Thieme. Swttgart 2004).

D LetfonJ of certain bratn '""J •nd •-T.ted behJllfor•l c!MngeJ (ilfter PCie
h;wior. The conditiCM'l may be a used by t\Jmors, dec~sed blood flow, ortr.-.uma. On the other hand. wmors l111101vfng the sept\Jm pelluddum ilnd hypCJthalamus (pink-shaded ane<~) and certilln forms Clfepilepsy may cause a disinhibition of anger, and the patient may respond to seemingly trivial events with attacks of "hypothalamic: rage• accompanied by screaming and bltfng. This outburst Is nCit directed against .-.ny particular persor1 or obfect and persists for some time.

313

Appendix List of References ................................... 387 Subject Index ...................................••. 389

List of References

Barr, M.l., ].A. Kiernan: The Human Nervous System, 5th ed. ]. B. Lippincott, Philadelphia 1988 Biihr, M., M. Frotscher: Duus' Neurologisch-topische Diagnostik. 8. Aufl. Thieme, Stuttgart 2003 Bear, M. F., B. W. Connors, M.A. Paradiso: Neuroscience. Exploring the Brain. 2. Aufl. Williams u. Wilkins, Baltimore 2000 Braak, H., E. Braak: Neuroanatomie. In: Demenzen (hrsg. von K. Beyreuther, K. M. Einhaupl, H. Forst! und A. Kurz) Thieme, Stuttgart2002, 118-129 Braus, D. F.: ElnBIIck Ins Gehlrn, Thieme, Stuttgart 2004 calabria, G., M. Rolando: Strutture e funzlonl del film lacrimal e. Proceedings of the 6th Symposium of the Italian Ophthalmological Society (S.O.I.), Genua 1984, 9-35 Delank, H. W., W. Gehlen: Neurologle, 1O.Aufl. Thieme, Stuttgart 2003 Duus, P.: Neurologlsch-toplsche Dlagnostlk, 7. Aufl. Thieme, Sbrttgart 2001 Faller, A., M. SchUnke: Der Kerper des Menschen, 14. AuH. Thieme, Stuttgart 2004 Fenels, H., W. Dauber: Anatomlsches Blldwiirterbuch, 9.Auf1. Thieme, Stuttgart 2005 Frick. H., H. L.eonhandt, D. Starck: Allgemeine und spezlelle Anatomle. Taschenlehrbuch der gesamten Anatomle, Bd. 1 und 2, 4.AuH. Thieme, Stuttgart 1992 Hempelmann, G., C. Krier, J. Schulte am Esch (Hrsg.): Gesamtrelhe alns. 4 B~nde, Thieme, Stuttgart 2001 Herrick, J, C.: Brains of Rats and Men. University of Chicago Press, Chicago 1926 lngvar, D. H.: Functional landscapes of the dominant hemisphere. Brain Res.107 (1976), 181-197 ]anlg, w.: VIsceral afferent neurones: Neuroanatomy and functions, organ regulations and sensations. In: Valtl, D., R. Schandry (eds.): From the heart to the brain. Peter Lang, Frankfurt am Main 1995, 5-34 Kahle, W., M. Frotscher: Taschenatlas der Anatomie, Bd. 3, 9. Aufl. Thieme, Stuttgart 2005 Kell. Ch. A., K. von Kriegstein, A. Riisler, A. Kleinschmidt, H.laufs: The Sensory Cortical Representation of the Human Penis: Revisiting Somatotopy in the Male Homunculus.]. Neurosci., ]un 2005; 25: 5984-5987 Klinke, R., S. Silbemagl: L.ehrbuch der Physiologie, 3.Aufl. Thieme, Stuttgart 2001 Klinke, R., H. C. Pape, S. Silbernagl: Physiologie, 5. Aufl. Thieme, Stuttgart2005 Kunze, K.: lehrbuch der Neurologie. Thieme, Stuttgart 1992

lang, G.: Augenheilkunde, 3. Aufl. Thieme, Stuttgart 2004 l..orke, D.: Schmerzrelevante Neuroanatomie. In: ains, Bd.4, Schmerz· therapie (hrsg. von H. Beck, E. Martin,]. Motsch, ].Schulte am Esch), Thieme, Stuttgart 2001, 13-28 Masuhr, K. F., M. Neumann: Neurologie, 5. Aufl. Thieme, Sbrttgart 2004 Maurer, j.: Neurootologie. Thieme, Stuttgart 1999 Meyer, W: Die Zahn-Mund- und Kiefer-Heilkunde, Bd. 1, Urban & Schwarzenberg, Miinchen 1958 Mumenthaler, M., M. Stohr, H. Miiller-Vahl: Uislon perlpherer Nerven und radlkulare Syndrome, B.Aufl. Thieme, Sbrttgart 2003 Nleuwenhuys, R., j. Voogd, Chr. van Huljzen: Das Zentralnervensystem des Menschen, 2. Aufl. Springer, Berlin 1991 Platzer, W.: Atlas der topograflschen Anatomle. Thieme, Stuttgart 1982 Poeck, K., W. Hartje: StOrungen von Antrleb und Affektlvltat. In: Kllnlsche Neuropsychologle (hrsg. von W. Hartje und K. Poeck), 5.Auf1. Thieme, Sbrttgart2002,412-422 Probst, R., G. Grevers, H.lro: Hals-Nasen-{)hren-Hellkunde, 2.Aufl. Thieme, Stuttgart 2004 RauberfKopsch: Anatomle des Menschen, Bd. 1-4, Thieme, Stuttgart. Bd.1., 2.AuH.: 1997, Bd.2 und 3:1987, Bd.4: 1988 Rohkamm. R.: Taschenatlas Neurologle, 2.Auf1. Thieme, Stuttgart 2003 Scheibel, M. E., A. B. Scheibel: Activity cycles In neurons of the reticular formation. Recent Adv Bioi Psychiatry. 1965; 8: 283-93 Schmidt, F.: Zur Innervation der Articulatio temporomandlbularls. Gegenbaurs morphol. ]b. 1967; 11 0: 554-573 Schumacher, G. H., G. AumOIIer: Topographlsche Anatomle des Mensch en, 6.Auf1. G. Fischer, 1994 Siegenthaler, W.: Kllnlsche Pathophyslologle, 8. AuH. Thieme, Stuttgart 2000 Steppe, G., F. Hentschel, D. L. Munz: Blldgebende Verfahren In der Psychlatrle. Thieme, Sbrttgart 2000 Tillmann, B.: Farbatlas der Anatomie Zahnmedizin-Humanmedizin. Thieme, Stuttgart 1997 von l.anz, T., W. Wachsmuth: Praktische Anatomie, Bd. 1f1 B Kopf. Gehirn· und Augenschadel. Springer, Berlin 2004

387

Subject Index

A Acceleration 140, 152, 3158 Accommodation 124, 127, 32a, 362 -connections 3152 -loss of 72 - neflex 361 Acervulus 224 Acetylchollne 273, 317, 318, 379 AOH (adrenocorticotropic hormone) 223 Action potential 174, 179 Adenohypophysis see Gland, pituitary, anterior lobe ADH (antidiuretic hormone) 222 Aditus to mastoid antrum 144 Adrenergic syndrome, reticular formation 230 Affect, suppression of, due to brain lesion 383 Afferent fibers 615, 233, 243, 274-279, 284 -of cranial nerves 78-89 -red nuclei 229 -subthalamic nuclei 225 -thalamic nuclei 218, 219 Ageusia 370 Air cells, mastoid 22 Airway 102 Ala, nasal 18 Alcohollsm 220 Allocortex 198, 199, 204, 205, 2015.207 -Alzheimer's disease 382 -Hippocampal formation 375 Alpha motor neuron see Neuron, motor Alveus of hippocampus 375 Alzheimer's disease 184 -atrophy of hippocampus 206 -cerebral ventricular system, enlarged 192 -changes In hippocampus 299, 383 -spread 382 Amacrine cells, retina1131 Amaurosis, unilateral 360 Amplifier, cochlear 367 Ampulla, membr;mous 153 -structure 152 Amygdala 70, 198, 207, 374, 379, 382 -- groups of nuclei 207 -- In coronal brain section 293 -- in sagittal brain section 1158. 310 --in transverse brain section 308 - - location 207 -- - relationship to ventricular system 193 -- analgesic system 335 -- connections -- olfactory pathway 372 -- stimulation 2a7 -- -with habenular nuclei 225

- --with hypothalamus 221 - - ampllfler function, emotional 207 Amylase 112 Analgesia 352 Analgesics 335 Anastomosis see specific vein Anatomy, sectional 292-315 Anemia 121 Anesthesia - epidural 291 - general 335 -lumbar 291 Aneurysm - rupture 262 - -Intracranial 191, 262 - -sites of occurrence 2153 Angle -Bennet 34 - cerebellopontine 82, 149, 239 - chamber 124, 128 - -trabecular meshwork 126 - of mandible 30 - - panoramic tomogram 39 -tumor (vestibular S[hwilnnoma.

acoustic neuroma) 149,239 Angularacceleratlon 14a, 152, 368 Anisocoria 128 Annulus see Ring Anorexia 221 Ansa - cervlcalls, deep 109 - lentlcularls 225 - -superficial 79 - --superior root 89, 1 09 Antihelix 141 Anti-Inflammatory medication 335 Antitragus 141 AP (area postrema) 196, 230 Aperture - anterior nasal 4, 19 -lateral, of fourth ventricle 194, 227 -median, of fourth ventricle 192, 194 - ohphenoid sinus 24, 29 - piriform (ante~or nasal) 4, 19 Apex - of dental root 37 - of orbital pyramid, coronal section 158 - of posterior horn 269, 271 -of tongue 104, 106 - petrous, of temporal bone 23, 145 Aphasia 251, 265 Aponeurosis -lingual 105 - palatine 1OJ Aqueduct - cerebral 72, 187, 192, 194, 21 0, 226,365 -cochlear 144, 148 - -arterial supply 25a - -In coronal brilln section 298

--In cross section of midbrain 234 --in sagittal section 315 --in transverse brain section 160, 3a8 --veins 155 -vestibular 148 Aqueous humor 124 -drainage 129 Arachnoid granulations 186, 194 ARAS (ascending reticular actlvatlon system) 218 Arborvitae ("tree of life") 240 Arborization, of cerebellar folia 24a Arch -aortic 2415 --pressure receptors, Innervation 815 --thrombotic material 264 - branchial, derivatives, oral floor muscles 1a9 -dental 37 -palatoglossal 102, 104, 11 a - palatopharyngeal 102, 1 04, 11 a. 115 - palpebral 61 -zygomatic 2, 11, 48, 97 --In coronal section 157, 158 --in transverse section 163 Archicerebellum see Brain, cerebellum Archlcortex (Archlpalllum) see Brain, cerebrum Area(s) - Kiesselbach's 61, 116, 119 -accommodation 230 -association 230 - Broca'sspeech 381 --blood supply 258 - Brodmann 329 -distribution, arterial 250 - entorhinal 374 -olfactory, connection --with habenular nuclei 225 --with hypothalamus 221 - postrema 196.230 - preolfactory 374 -preoptic 210 - preplrlform 70, 372 - pretectal 361, 3152 -sensory 209 -septal 372, 374 -striate 203, 358 --In coronal brain section 301, 3a3 --in transverse brain section 308 -subcallosal 372, 374 -vestibular 227 - Wernlckl!, speech 251, 381 Areflexia 352 Argyll-Robertson pupil 362 Arm, difficulty rilising 88 Arousal function 361 Arousal system 216 Arterial circle see arcle, arterial Arteritis, Horton's temporal 59

Artery (arterlesl - Ademldewlcz (great radicular artery) 2815 -alveolar 58 -- Inferior 58, 95, 97, 98, 156, 158 ---distribution 58 ---in sagittal section 1159 ---mental branch 58, 92, 95 -- posterior superior 58, 97, 98, 100 ---distribution 58,100 -angular 54, 56, 65, 92, 95, 120 --anastomosis with dorsal nasal artery 56 --distribution 57 - aurlcublr 54, 141 --anterior 141 -- branch(es) 515 --deep 58,154 ---distribution 55, 57 ---perforating 141 --posterior 54, 56,141 ---perforating 141 -candelabrum 249 -cerebellar 195, 247, 252 --Inferior ---anterior 155,195,247,248, 252 ---posterior 195,247,252 --distribution 253 --superior 195, 247, 248, 252 ---distribution 253 -cervical, ascending 286 - conjuctlval, anterior 132 -facial 54, 56, 65, 92, 95, 98, 120 -- branches 56 --distribution 55, 57 -- pulse, taking of 56 - hypophysol 150, 223 -laryngeal --superior 57 - nas.al,lateral posterior 58, 100, 117 --distribution 58, 1 00 -of (pre/post)central sulcus 249 -parietal, posterior 249 - pauage d!rough skull base 90 -pharyngeal, ascending 54, 56 --distribution 55, 57 -- pharyngeal branches 57 --variants in origin 57 - polar frontal 249 -segmental 286 -spinal 286 --occlusion 287 - sulcocommlssunol 287 -basilar 155, 195, 246,248, 251, 252,286 -- branches 252, 253 --distribution 253 --In transverse section 1151, 162 - bucc.l 58, 98, 1 00 --distribution 58, 1 00 - undelabrum 249 - ullosomarglnal 249 -caroticotympanic 60, 154

389

A Artery (arteries)

-carotid --common 54, 56, 65, 246 --- In saglttillsectlon 169 --external 54,61, 65, 141, 246 --- branches 51, 55, 56 --- -anastomoses 55 --- -superficial 95 ----variants 55 --- distribution 93 --- terminal branches 55, 58 --internal 10, 21, 22, 54, 60, 65, 93,101,117,134,137,144, 149 --- aneurysm 263 ---brain of base 248 --- branch(es) 60 --- distribution area 264 --- In saglttillsectlon 168 ---In transverse section 161, 162,164 ---occlusion 164 --- part(s) 60, 246 - - - - petrous 60, 154, 246 --- stenosis 264 --- - Intracranial 264 --- thrombosis 1 64 -central --anterolateral 251 ---striate branches 251 --posteromedial 251 -cerebellar --superior 195,247, 248, 252, 253 -cerebral 191 --afferent 246 --anterior 195,247,251 --- branch(es) 249 --- distribution 250 --- occlusion 251, 265 ----embolle 264 --- part(s) 248 --middle 195. 247 --- aneurysm 263 --- branch(es) 186, 249 --- distribution 250, 264 --- In lateral sulcus 249 --- occlusion 251, 264 --- part(s) 248, 251 --posterior 195, 246, 251, 252 --- branch(es) 245 --- - Interpeduncular, distribution 253 --- occlusion 251, 265 ---origin 249 --- part(s) 248 --- semicircular duct 250, 253 --superficial course 248 -choroidal --anterior 60. 195. 248 --- branches 251 ---distribution 251 --posterior 253 -ciliary --anterior 132 --posterior 61 132, 137 ---short 61,132,137,139 - cochlear 155 -communicating --aneurysm 263 --anterior 247, 248 --posterior 60, 195,246, 248 --- distribution 253 --- perforating branches 251 -crural 154

390

-deep lingual 57, 106 -donal nasal 56, 61, 92,120, 137 -- anastomosis with angular artery 56 -ethmoidal -- anterior 61, 11 6, 137 -- - meningeal branch 1 90 --posterior 14,61,116,137 -facial 54, 56, 65, 92, 95, 98, 120 -- distribution 55, 57 -- pulse talclng 56 -- -distribution 57 - frontobual 249 -- distribution 253 - lnfrao.tlital 1 4, 1 7, 58, 92, 98, 100,120 -- distribution 58, 1 00 -labial 54, 56, 95 -- distribution 57 -labyrinthine 154, 252 -- origin 252 --vasospasm 149 -lacrtmal 137, 139 -- communicating branch with middle meningeal artery 59, 61 -laryngeal -- superior 57 -lenticulostriate 251 -- rupture 263 -lingual 54, 56, 1 06 -- branch(es) 57 -- distribution 55, 57 -lumbar 286 -masseteric 58, 100 -maxillary 54, 56. 58. 61, 95. 97, 98,117 -- mylohyoid 58 -- posterior septal 117 --pterygoid 58, 100 -- -distribution 1 00 -- distribution 55, 58 -- part(s) 58, 100 - - transverse section 165 --variants 99 -menlngNI -- middle 8, 58, 90, 91, 97, 98, 137 -- -anastomotic with lacrimal artery 58, 61, 137 ---frontal 186, 190 ---parietal 186, 190 -- distribution 58 -- in sagittill section 168 -- - rupture 186, 262 -- posterior 57, 190 -- -distribution 57 -nasal, lateral posterior 58. 100. 117 -- distribution 58, 1 00 - nasopalatine 90 - ocdpltal 54, 56, 94, 96 -- branch(es) 57 -- -descending 57 - - - mastoid 190 -- -occipital 55, 57 -- distribution 55, 57 -- In transverse section 1 65 -- lateral 248 -- medial 248 -of bralnstem 252 -of pterygoid canal 59, 60, 100

- ophdlalmlc 14, 60, 65, 93, 133, 138 - - branches 137 - -distribution 61 -palatine - -ascending 56, 57 --descending 17, 58,100,116 --greater 58,100,103,116,156 - --distribution 58, 100 --lesser 17, 58,100,103 - --distribution 58, 100 -palpebral --lateral 61,93 - - medial 61, 93, 137 - pertcallosal 249 -pontine 247, 252 - prefrontal 249 - radlwlar - -anterior 287 --great 286 - - posterior 287 -sphenopalatine 17, 58, 61, 98, 100,117 - - posterior septal branches 58, 100,116 - --distribution 100 -spinal - -anterior 247, 252, 286 - --distribution 253 - -occlusion 287 --posterior 247, 286 - stylomastoid 147, 1 54 - -distribution 57 - - posterior tympanic branch 1 54 - subarcuate 154 - subdiiVIan 54, 246, 286 - -stenosis 247 -sublingual 57, 106 - submental 56, 95, 106 - -distribution 57 -sulcal 287 - superftd•l petrosal 1 54 - suprao.tlltal 14, 59, 61, 93, 120,137,139 -supratrochlear 14, 56, 61, 93, 137,139 - sympathetic effects on 325 -temporal --deep 58, 97,98,100 - --distribution 58, 100 - - middle 59, 95 - -superficial 54, 56, 58, 92, 94, 97, 113, 141 - -- branch(es) 58, 94 - --distribution 55, 58 - --In transverse section 163 - thalamic 117 -thyroid - -ima 57 - -superior 54, 56, 246 - -- branch(es) 57 - --distribution 55, 57 - --variants In origin 55 - trans...,ne facial 58. 92, 94 - -distribution 58 - tubartan 154 -tympanic - -anterior 58, 154 - --distribution 58 - -inferior 57, 1 54 - --distribution 57 - - posterior 56, 1 54 - --distribution 57 - --stapedial branch 154

--superior 154 -vertebral 54, 190, 195, 246, 248, 252, 286, 290 --branches 248 --branches 248 --- paranldlen 252 --In saglttill section 167 --In transverse section 1 64 --proximal stenosis 247 -vestibular 155 - vestlbulocochlear 1 55 -zygomatico-orbital 58, 94 Articular disk, oftemporomandibular joint 33, 35, 48, 50 Aspartic acid 241 Association cells 271, 273 Asthenia 245 Astrocyte(s) -end-feet 189 -fibrillary 176 -function 177 -protoplasmic 1 76 Asynergy, muscular 245, 353, 355 Ataxia 244, 245, 353 -cerebellar 353 -funicular, lateral 355 -gait 244, 245 -lower limb 244 -sensory 330, 353 -stance 244, 245 -truncal 244, 2451 Atlas -relationship to vertebral artery 246 -sagittal section 1 66 -transverse section 165 Atony, intestinal, postoperative 324 ATR (Achilles tendon reflex) 272 -loss of 347 Atrium, left, thrombotic material 264 Atrophy -of hippocampus 383 -of pectoralis major 346 Atropine, effect on bronchial secretion 325 Attic (of middle ear) 147 Auditory apparatus 140,148, 150 -afferent impulses 149 Auditory pathway 213, 214,219, 227. 233, 235, 275, 308, 366 - stations 366 - tonotopic organization 366 Auditory testing, objective 367 Auricle 78, 140 -arterial supply 141 -cartilage 141 --transverse section 164 -innervation, sensory 142 -lymphatic drainage 142 -muscles 141 Auricular cartilage see Cartilage, auriculiilr

Axis - brainstem (Meynert) 1 85, 226 -hypothalamic-posterior, pituitary 222 -oflens 127 -optical 125 -orbital 125 -relationship to vertebral artery 246 Axon 173

Broinstem

-central 332 -dendritic 180 -long 175 - myelinilted 176, 180 - nonmyelinated 176, 180 -parallel contiiCt 175 -short 175 Axon collaterill 271, 273 -descending 276 Axonal hillock 174 Axon-Merkel cell complex 328

B Balance -cerebellar function 239, 244 -regulation of 368 -- ilutonomlc 369 -sense of 179 Band, of Broca, diagonal 374 Bands, lymphatic, lateral 11 0 Basal ganglia see Ganglia, basal Basal nuclel see Nucleus, bilsal Basal skull see Skull, base Base of Salzmann, vitreous 1 25 Bechterew, nucleus, 68, 82, 228, 369 Behavior -affective 374 -brain area lesions 383 -change 208 Bell phenomenon 79 Belly -anterior, of digastric muscle 51, 108.157,158 -- innervation 74, 95 -frontal, of ocdpltofrontalls 44, 47 -occipital, of occipitofrontalis 45, 47,52 -posterior, of digilstric muscle 53,108 -- innervation 78, 95 Betz giant cells 338 Betz pyramidal cells 200 Bifurcation, carotid 54, 246 -atheromatous change 264 -stenosis 247 Bladder -Head zone 323 -weakness 265 Blind spot 1 24, 130, 359 Blindness 129,131,133,251 -unilateral 360 Blinking 121 -reflex 46, 121 Blood flow -cerebral 378 --decreased 247, 264 -- cardinal symptoms 265 --cause 264 -Intestinal 324 Blood pressure regulation 31 9 -sympathetic effects 325 Blood serum, laboratory values 197 Blood-brain barrier 196 Blood-CSF barrier 1 91 -demonstration 196 Bochdalek's flower basket 1 95 Body/Corpus - [body] carotid 54, 84 -- chemoreceptors, Innervation 86

- [body[ cell see Perikaryon -[body[ dllary 121, 124, 126, 128,130 - -epithelium 126 - --pigment 124 --pars ---plana 126 - -- pllcata 126 - [body[ genlculm! --lateral71,131,212,216,219, 297,300,308,311,358 - --connection with cerebral cortex 219 --medial 71,213, 216,219, 297, 300. 308. 313 - --connection with cerebral cortex 219 - [body[ Herring 222 - [body[ m•mmlll•ry 1 99, 204, 205,206,210-215,217-221, 295, 299, 309, 374 - - bilateral lesions 220 - -connections - - hemorrhage 220 - -In coronal brain section 295 - -in midsagittal section 295 - --with dorsal longitudinal fasciculus 321 - --with thalamus 218 - [body[ of caudate nudeus 208 - -in coronal brain section 293, 294,296 - -in transverse brain section 304 - [body[ of fornix 205, 295, 305, 314 - [body[ of hyoid bone 31 - [body[ oflncus 146 - [body[ of mandible 30, 1 58, 169 - [body[ of sphenoid bone 19, 25,163 - [body[ of tongue 104 - [body[ pineal (pineal gland) 183,192,196,210,212,214, 224,227,297,308,315 - [body[ tr•pezold 235 -[body[ vitreous 124, 125, 156, 160,162,168 --attachment 125 - -coronal section 1 56 - -sagittal section 1 68 --transverse section 160, 162 -[corpus] callosum 192, 199, 204,206,210,212,214, 299, 309, 374, 376 - -arterial supply 250 - -coronal section 1 59 - -function 380 - -in coronal brain section 292, 294, 296, 300 --In sagittal brain section 166, 312,314 - -in transverse brain section 304 --rostrum 205, 314,377 - -splenium 380 - -surgical division of 380 - -topography 205 -[corpus[ strlilltum (striate body) 198,208,283,292,312,337, 339,340 - - phylogenetic origin 199 Body position 21 7, 229 Body sensation, conscious 184

Body temperarure, regulation of 221 Bone(s) - alveol•r 37 - aanlal 2, 186, 189 --ossification 3 --table 186,189 -ethmoid 2, 3, 4, 13, 16, 27 --nasal septum 18 --plate ---orbital 15, 16, 21, 27, 156 --- perpendicular 4, 16, 1 8, 21, 27,114 - fronbl 2, 3, 4, 8, 10, 13,22 --orbital part 15 --orbital surface 16 -hyoid 3,31,102,105,106 --cornu 168 --sagittal section 166, 168 - Interior view 12 -lalt 14 --transverse section 165 - p.alatlne 3, 6, 10, 24, 28 --nasal septum 18 -- pell)endlcular plate 19, 20 - p.artetal 2, 3, 4, 8, 10, 24 - petrous 3, 7, 1 0, 13, 22, 78, 140, 144, 148 - - blood supply 154 - sphecold ("wasp bone") see Bone, sphenoid -sphenoid 3. 6. 10, 13, 24 --integration of pyramidal process Into palatine bone 28 --location 24 --nasal septum 18 --orbital surfilce 25 --transverse section 162 --wing ---greater 2,4, 13, 16,24,48, 100,162 --- lesser 4, 12, 19, 25 -temporal 2, 3, 4, 6, 8, 10, 13, 22,24 --location 22 --ossification centers 22 --part --- milstold 3, 10 --- petrous (petrous bane) 3, 7, 10, 13, 22, 78, 140, 144, 148 --- -sagittal section 1 69 --- -superior border 12 ----transverse section 162 ---squamous 2, 6. 10. 22 ---tympanic 3, 10, 22 - trtbasllar 24 -tymp~nlc 143 -zygomatic 2,3,4,5, 10,14 --surface ---orbital 16 ---temporal 1 1 Bone growth, disturbance 1 1 Boundary, telodlencephallc 21 1 Bouton 174 -en passage 175 Bowman membrane 127 Brachium of colllculus -Inferior 212, 21 9, 227 --cross section of midbrain 234

B

-superior 227 Brain 172,184-186,198-245, 292-315, 382 - iiCtivity, neuronill 329, 379 see also Brain. function

-adult 198 - atrophy 184 -axes 198 - blood vessels of 246-265 --arteries 54, 60, 246-253 ---aneurysms 263 -- blood flow 378 -- Intracranial hemorrhage 262 --- extracerebral 262 ---intracerebral 263 --veins 62, 63, 256, 258-261 - brainstem see Brainstem -cerebellum see Cerebellum -cerebrum see Cerebrum -development 1 83 - diencephillon see Diencephalon -directions 1 85 -edema 1 84, 265 -embryonic -fibers 376,377 -function -- balance regulation 369 -- behavior 374, 382, 383 -- memory 374 --motor 181,336,341,342 --sensory 1 81 --taste 370 --smell372 --visual 71, 358, 360 -herniation 1 89, 197 -medulla oblongata see Medulla oblongata -mesencephalon see Mesencephalon -metencephalon see Metencephalon - myelencephillon -nerves of 66 see also Nerves, cranial -organization --functional 199 -- macroscopic 184 - pons see Pons -prosencephalon see Prosencephalon -projection onto skull 187 -rhombencephalon see Rhombencephalon -sections --coronal 51,156-159,261, 263,292-303,326, 331, 333, 334, 335, 340 -- (mld)saglttal 166-169, 185, 310-315 --transverse 160-165,259, 304-309 -stroke 264 -structures, internal 193, 195-197 -- projection onto skull 1 87 -telencephalon see Cerebrum -tissue 196 -tumors 176 Bralnstem 184,212, 213, 226-237 -axis Jg8, 226 - blood vessels of --arteries 252, 253 --veins 260, 261

391

B Brainstem

-compression 189, 239 -cranial nerves 227, 320 see also Nerves, cranial - development 68 -divisions 226 -function --auditory 366, 367 --motor 337-339, 341 --sensory 327,331,337 --gustatory (taste) 370 --vestibular (balance) 368, 369 --visual 361, 364, 365 - herniation 189, 197 - lesions 226, 330 -levels 226 --medulla oblongata see Medulla oblongata --mesencephalon see Mesencephalon --pons see Pons

-nerves --cranial 227 see also Nerves, cranial --of autonomic nervous system 317 --of parasympathetic nervous system 320 -nuclei --of cranial nerves 67-69, 228, 232 --motor 281 --parasympathetic 316, 320 --thalamic 216 -organization 226, 227 - position 239 - projection onto skull 1 87 -reflexes 361 -sections --coronal 297, 298 -- (mld)saglttal 226, 228-233, 240, 253, 295, 31 2-315 --transverse 163. 229, 231. 234, 253, 260, 308,309,319, 326, 333,343 -structure, external 212, 213, 226,227 -tracts 232, 233 Broca -speech areas 381 -diagonal band of 374 Bronchodllatlon 325 Bronchoscopy 325 Brown-Sequard syndrome 355 Brush border, choroid plexus 195 Bulb -Inferior, of jugular vein 288 -of !!)'I! (l!)'l!ball) 124,136 --connections 373 --coronal section 157 --phylogenetic origin 199 --sagittal section 166 -olfactory 183 -superior, of jugular vein 144, 187,256 Bundles, pallidotegmental 225

392

c Calcification 224 Calvaria 8, 9 Canal(s) -auditory, external 2, 13, 23, 32, 80, 140, 144, 147, 148 -- curvature 43 - - innervation, a.~taneous 86

--lymphatic drainage 142 --transmitted structures 90 - carotid 60, 144, 246 --topographic relationships 10 - centnol 192, 194. 266. 269 -- development 182 -- in cross section of medulla oblongata 237 --In sagittal section 315 - cochle.r 150 -condylar 11, 26, 257 -facial 80, 99,144,145 -Incisive 19, 29 -Infraorbital 14, 1 6, 76 -- coronal section 156 -mandibular 30, 77 -- coronal section 156

-- panoramic tomogram 39 - nasolacrimal 14 -nerve --facial 80, 99, 145 -- hypoglossal 11, 13, 26, 89 -ofCioquet 125 -optic 1 3, 25, 29, 71 -- In transverse section 161 -pal.tlne --greater 17,19,29 --lesser 17 -pterygoid 17, 25, 29,80 -Schlemm 124,126,128 -semlclrcul.r 140,148,152,368 --lateral 144 -vertebral, periosteal lining 191 -VIdian 17, 25, 29, 80 --transmitted structures 101 Canaliculus -tympanic 85 Canines see Teeth Cannon-Bohm point 86, 321 Canthus see Commissure Capsule -articular, of temporomandibular joint 32, 35, 49 -external -- in coronal brain section 293, 296 -- In sagittal section 168 -- In transverse brain section 305 - extftme 209, 292-296, 305-307 -- In coronal section 292, 296 -- In sagittal section 168 -- in transverse section 305 -internal 207,211,215,224, 281, 329, 333, 376 -- anterior 11mb 292, 293, 305, 306,307,311 -- -In coronal brain section 292 -- -in transverse brain section 305 -- arterial supply 250 -- posterior limb 294, 297, 605, 307,377

- --in coronal brain section 296 - --In sagittal brain section 313 - --In transverse brain section 305 --tracts, motor 281, 294,338 - - - lesion 343 - --supplementary 281 - -cerebral Infarction 263 - -course of pyramidal tract 294, 338 - -hemorrhage 329 --section - --coronal 159, 292, 294, 296 ---saglttal167,168,310,313 - --transverse 304 - -soma-pic organization 377 -Tenon 136 Carcinoma - prostatic Invasion of sacral venous plexus 289 - squamous cell - -oral cavity 102 --tongue 107 Cardinal directions of gaze 135 Carotid siphon 159, 246 - stenosis 247 Carotid sheath 62 Carotid territory 246 Cartllage(s) - alar, of nose 18 --crus ---lateral 18 ---medial19,164 -auricular 141 --transverse section 164 - epiglottic, sagittal section 167 - laryngeal, sagittal 1 66 -nasal 18 -septal, of nose 18, 114, 117 --transverse section 163 -thyroid - -left lamina, sagittal section 168 - -sagittal section 167 Caruncle - lacrimal 1 22 -sublingual 106, 112 Cataract 127,129 - glaucomatous 129 Cauda/Tail -[cauda] equlna 172, 191, 266, 269, 290, 291, 344 - -compression 345 - -lesion 357 --syndrome 267,345 - [tail] of caudate nucleus 208, 329 - -In coronal brain section 296, 298 - -in sagittal brain section 311 - -in transverse brain section 305 - -relationship to ventricular system 193 Cavity/Chamber - [cavity] nasal 4, 18, 19, 20, 21, 118,156,158,161,162,164 - -coronal section 156, 158 - -functional states of mucosa 118 --mucosa 115 - -nerve supply 116 --transverse section 161, 162, 164 - - vascularsupply 116

-[cavity] oral 29,102,110,156, 167 --coronal section 156 -- lymphatic tissue 11 0 -- agittalsection 167 --squamous cell carcinoma 1 02 -[cavity] tympanic 22, 143, 144, 146 --course of chorda tympani 80 --division of glossopharyngeal nerve 85 --levels 147 --mucosal lining 147 --relationships 145 --walls 144 -[chamber] !!)'I! 124,126,128 -[chamber] pulp 37 --proper 102 Cavum septl pellucid I 205, 215 Cell badly see Perikaryon Cementum (cement) 37 Central scotoma 360 Cerebellar peduncle see Peduncle, cerebellar Cerebellum 184, 185, 238-245 - afferents 241. 244 - archicerebellum 239, 244, 368 -blood vessels --arteries 252, 253 --hemorrhage 262, 263 --veins 260, 261 -classifications (phylogenetic, anatomical, functional) 239, 244 -connections 218,241 -cortex 183, 240,241 -development 183 - efferents 241 -fibers 241 -folia 240 -functional anatomy 244 -herniation 189 -layers 241 -lesions 245 -movement, Involvement In 336, 377 -neurons 241 -nuclei 183, 240, 245 -peduncles see Peduncles, cerebellar -projection onto skull 187 -sections --coronal 297-303 --(mid)sagittal 166-169. 185, 192, 226, 230, 240, 253, 310-315,326 --transverse 160-164, 253 -sensorimotor function 336, 337 -structure --external 238, 239 --internal 240 -tracts 279, 283, 284, 326, 327 -white matter 240, 312 Cerebral centers. functional, blood supply 251 Cerebral ventricular system see Ventricular system, cerebral Cerebrocerebellum 239 -deficit symptoms 244 Cerebrospinal fluid see Fluid, cerebrospinal Cerebrum (cerebral cortex. tel encephalon) 185-189, 1 98-209, 213-218,315

Carpus striatum C

-areas 378, 382 --Broca 251 -- Brodmann 202, 203, 329, 374 --motor 336 --speech 381 --WernickE 251 -association fibers 376 -blood vessels --arteries 248-251 -- -intracerebral hemorrhage 263 -- -occlusion 265 -- disturbance of blood flow 264 --veins 258, 259 -- -venous thrombosis 265

-centers --functional 251 -- modulating subcortical 379 -columns 175, 201, 329 -cortexes --allocortex 199,204-207 -- archicortex (archipallium) 198, 1 99, 204-207. 374, 375 - - Isocortex 199, 204 -- neocortex (neopallium, cortex) 1 98-203, 250, 374 -- paleocortex (paleopallium) 1 98, 199, 204, 207' 374 -cytoarchitecture 200, 203 -development 1 83, 198 -divisions, phylogenetic 198. 199

-function -- motor 336, 337 -- sensory 329 -histology 200 -Ischemia 264, 286 -lobes --frontal 51, 57, 70,156-158, 184,187,192,198,219,249, 304,310 -- - prefrontal 335, 336, 382, 383 -- insular (insula) 184, 198, 199, 249, 250, 293, 294, 307. 31 0 -- limbic (limbus) 1 99 --occlpttal163, 184,192,198, 1 99. 260. 304, 305. 306. 31 0 -- - lesion 360 --parietal 159,184,198,199, 210, 219,249, 336 --temporal 51,57, 114,159, 184,187,189,192, 193,198, 1 99, 207' 249, 260 -nerves 66, 67, 70, 71 see also Nerves, cranial -neurons 200-203 -- groups 175 -organization 378 -- columnar 201 --functional 200 -- microscopic (cytoarchltectonics) 203 -paralysis 79 -parts 215. 315 -phylogenetic origins 198, 199 -projection fibers 376 -sections -- coronal 173, 1 98, 203, 207, 209, 215,251' 292-303, 304, 326,333-335,338,339 -- (mid)sagittal 166-169, 226, 310-315 --transverse 114, 207, 209,212, 251. 260, 304-309

-strokE 264 -tracts 275, 277, 281, 283 Cerumen 143 - impaction 143 -glands 143 Chamber see Cavity Cheek. Innervation, sensory 1 03 Chemoreceptors 54, 84 - in carotid body 86 Choana (internal naris) 1 1, 1 9, 28, 110,115 - In sagittal section 166 - In transverse section 1 64 Cholinergic system, reticular formation 230 Chondrocranium 3 Chorda - notochord 182 -tympani 22, 74, 78, 80, 109, 144,147,155,320 --gustatory fibers 81, 370 - -innervation of tongue 1 06 - - passage through skull base 90 Choreoathetosis 229 Choroid of eye 124, 128, 131, 132 Cilia, olfactory cells 373 - pigment epithelium 124 Cingulum 377 Circadian rilythm 224, 300 Circle, arterial, of Zlnn·Hilller, 132 Circulation, portal, pituitary 223 Circulatory center, reticular formation 231 Circulatory homeostasis 318 Clrcumventrlcular organ 1 96 Clsterna(e) 194 - ambient 194 -basal 194 -carotid 195 - cerebellomedullary 194 - chiasmatic 1 94 - - relationship to internal carotid artery 246 -crural 195 - Insular 307 - Interhemispheric 194 -interpeduncular 194 - lumbar 1 91, 290 - magna (cerebellomedullary) 194 - median pontine 195 -of corpus callosum 195 -of lamina termlnalls 194 -of lateral cerebral fossa 195 - olfactory 195 - pontocerebellar --In sagittal section 167 - -In transverse section 163 - pontomedullary 194 -spinal 195 -subarachnoid 195 -trigeminal 195 -vermlan 194 Claustrum 198, 263 - arterial supply 250 - in coronal brain section 292, 296 - in sagittal brain section 1 68, 31 0 - In transverse brain section 306 Clawhand, Dejerine-Kiumpke brilchlill plexus paralysis 349 Cleft lip repair 46 Cleft, synaptic 1 75 Clivus 13 - In sagittal section 166 - In trilnsverse section 1 62

Cloquet, casal of 125 CN I see Nerve, ollfactory CN II see Nerve, optic CN Ill see Nerve, oculomotor CN IV see Nerve, trochlear CN V see Nerve, trigeminal CN VI see Nerve, abducent CN VII see Nerve, facial CN VIII see Nerve. vestibulocochlear CN IX see Nerve, glossopharyngeal CN X see Nerve, vagus CN XI see Nerve, accessory CN XII see Nerve, hypoglossal Coat -fibrous, ofthe eye 1 24 -inner, of the eye 124 - mucosa, lingual 105 -vascular, of the eye 124, 128, 130 Cochlea 83, 144, 148, 150, 366 -formation of traveling wave 151 - location 150 -structure 150 Cochlear turns 150 Coding of teeth -deciduous teeth 43 - permanent teeth 38 Cold - receptors 328 -sensation 179 Colliculus (colliculi) -facial 227 -Inferior 212, 227, 229, 308 - - blood supply 253 --In coronal brain section 300 --in sagittal brain section 314 -superior 212,227,229,308, 361 --In coronal brain section 299 --In sagittal brain section 314 --in transverse brain section 308 Column(s) -cortical 175, 201 --activity In primary somatosensory cortex 329 - nuclear 270 -of fornix 205. 206.294 -of spinal cord 268 Coma, testing of brainstem function 361 Commissural cells, 271, 273 Commissure/Canthus -[canthus[ medial, of eyelid 121 - [canthus]lateral, of eyelid 121 -[commissure] anterior 206, 210, 214, 274, 374, 377 -- ilrterlal supply 250 --in coronal brain section 294 --in sagittal brain section 313, 315 -[commissure] eplthalamlc 224, 377 --in coronal brain section 297 -[commissure] habenular 224 -[commissure] of fornix 205, 374 -(commissure( posterior 224, 377 --In coronal brain section 297 -[commissure] white 271 Commissurotomy 380 Communication pathways within the brain, disruption of 208 Concha - aurlculilr 141

-nasal --Inferior 3,4,5, 10, 16, 18,20, 114,116 ---in coronal section 156 ---in sagittal section 167 ---In transverse section 164 ---opening of nasolacrimal duct 122 --middle 4, 5, 16, 19, 21, 27, 114,116 ---in coronal section 156 ---In sagittal section 167 --superior 16, 19, 21, 27,115 Condyle, ocdpital 6, 1 1. 26, 157 Cone, retinal 131, 358 Confluence -of dural sinuses 9, 65, 186, 194, 247' 254-257' 260, 302 -- In sagittal section 1 66 -posterior venous 259 Confrontation test, visual field examination 359 Conlocortex 200 Conjunctiva 121, 129 -of eye 121,124,128,130 Conjunctivitis 121 Connections, afferent 225,241 Consciousness 218 -modulating subcortical centers 379 Constipation. due to medications 324 Constriction -papillary 1 28, 320, 362 Contraction, tetanic, muscle 273 Conus medullarls 269 -location 291 Convergence 362, 365 -connections 362 -signal 131 Coordination 217 -autonomic 210 -gaze 217 -movements 239 Cord(s) -cervical 184, 269 --anterior hom, somatotopic organization 279 --course of pyramidal tract 338 --gray matter, cell groups 271 --groups of nuclei, Rexed laminae 271 -- lesion 356 --motor tract 343 -lateral, of brachial plexus 348 -lesion, complete 356 -medial, of brachial plexus 348 -posterior, of brachlill plexus 348 -sacral 296 -thoracic 269 288, 267 --groups of nuclei, Rexed laminae 271 -- lesion 356 ---of motor tracts 343 Corium 121, 124, 1 28, 130, 136 Cornea 121,124,126,127,128, 130,132 Cornu see Horn Coronii/Crown -[corona( radiata 376 -[crown] dental 36 Corpus callosum see Body/Corpus Corpus striatum (striate body) see Body/Corpus

393

C Corpuscle

Corpuscle - Meissner 328 -Ruffini 328 Correlation system, intersegmental 271 Cortex of lens 127 Cortex - allocortex see Allocortex - archlcortex see Brain, cerebrum - assodatlon 378 --limbic 378 --parietal 329 -- parletotemporal 378 --planning of movements 336 --prefrontal 378 --visual 361,381 -audlto!1'203, 219 --primary 366, 378 -cerebellar see Cerebellum -cerebral see Cerebrum - conlomrtex see Coniocortex -- entominal 379 ---Alzheimer's disease 382 - Insular 294, 366, 370, 382 --In coronal brain section 293 - Isocortex see Brain, cerebrum -motor 336-343 --multiple sclerosis, involvement In 208 --neurons 175 --nuclei 340,341 --primary 200, 203, 232,331, 378 --pyramidal tract 280 -- struct\Jre 200, 339 --supplementary motor 336 - - - motor loop 341 -neocortex see Brain, cerebrum -olfacto111 - paleocortex see Brain, cerebrum - prefrontal 335, 336 --emotions 382 - premotor 336,341, 378 --thalamic nuclei 21 9 - Hnsorlmotor blood supply 251 - HI1SD!1' 1 81, 27 5, 277, 326 - sornatomotor 336. 375 --blood flow 378 -- motorloop 341 - sornatosenso111 21 9, 277 --primary 200, 203, 27 5, 329, 378 -vlsual203,219,251,303,358, 375,378 --decreased blood flow 2S1 --In coronal brain section 303 --primary 203 --somatosensory 21 7, 21 9 --- blood flow 378 --- projections from thillamus 218 Corti organ 148, 150,366 -fibers from the olive 367 -structure 151 Corti tunnel 1SO Cortical fields 202 Cortical margin -arterial supply 250 -decreased blood flow 251 Corticotropin 223 Cranial bones see Bone(s), cranial Cranial nerves see Nerves, cranial Cranium see Skull Crest/Crista

394

-(crlsta(galll13,16,19,27,114, 188 -- In coronillsectlon 157 -- in transverse section 1 60 -(crest]ampullary 148, 368 -- orientation of stereocilia 153 -- structure 1 52 -(crest] external occipital 26 -[crest] frontal 8, 13 -(crest] infratemporal 17, 48 -(crest]lacrimal 2S, 46 -(crest] nasal 1 9, 29 -(crest] sphenoidal 19, 25 -[crest] transverse, of internal acoustic meatus 14g Crista see Crest Crown see Corona Crus (crura) - - of stapes 146 - cerebri see Peduncle, cerebrill -long, of incus 146 -ofantihelix 141 -of fornix 205, 206, 297, 298, 306 --In sagittal brain section 313 - - of stapes 146 -short, of incus 146 CSF see Fluid, cerebrospinal Culmen 238 Cupula 152 Cusp-and-fissure occlusion of teeth 37,39 Cuspids see Teeth Cyanoslsofllps 102 Cyst, colloid of plt\Jitary 222 Cytoarchitecture, cortical 200, 203

D Decussation -in cross section of medulla oblongata 237 -of Forel 283 -of pyramids (decussiltlon of pyramidal tract) 189, 227, 232, 237,281,338 -of superior cerebellar peduncle 243 Deep sensation see Proprioception Defecation, spinal cord tract for 283 Deformity, cranial 7 Dejerlne-Kiumpke brachial plexus paralysis 349 Dendrite 1 74 Dendritic ;~xon see Axon, dendritic Densofaxis 111,115 -sagittal section 166 -transverse section 165 Dentine 37 Depression 382 Dermatome 267, 323, 344 -overlap 34S Desmocranium 3 Diabetes Insipidus 221 Dlaphragm/Diaphragma -(diaphragm! Head zone 323 -oralfloor 108 -(dlaphragma] sellae 188 -spinal cord segments 357 - weilkness of 346

Diencephalon 185, 210-225, 240, 294,315 -axes 198 - blood supply 258 -development 183,209, 211 - embryonic 211 - epithalamus see Epithalamus -function 214 - -motor 340, 341 - -sensorimotor 337 -- somatomotor 181 --ventricular system 192, 193 - globus pallidus see Globus pallidus - hypothalamus see Hypothalamus - insit\J 210 - lesions 330 - location 213 -nerves 66, 67,71 see also Nerves, cr;mlal -parts 210, 21 1, 315 - pit\Jitary gland see Gland, pituitary -sections --coronal 211,214,215,217, 220, 224, 225, 294-298, 326, 331. 334, 335.339.340 -- (mid)sagittal 210, 220-22S, 295, 299, 312-315 --transverse 160,305-309 - struct\Jre - -external 212, 213, 297 - -internal 214 - subthalamus see Subthalamus -thalamus see Thalamus -tracts 275, 277, 281, 283 Digestive t\Jbe, innervation 321, 324 Digitations, hippocampal 193 Dilation, papillary 72, 128 Dlplo@ 9, 186, 1 89 Dlploplil 72 Discrimination 218 Discrimination, two-point 179 - Impaired 353 -tracts for 276 - unilateral loss of 330 Disinhibition of r;~ge, brain lesion 383 Disk, herniated 345 Dislocation of temporomandibular joint 33 Distance vision 127 Dopaminergic system, reticular formation 230 Dorsal column nuclei 181,276 Dorsal root 67,182,191 , 275, 290, 31 7. 322, 332, 344 - sprouting ofilfferent axons 182 Dorsum -of tongue 102,104 - sellae 12, 25 Drive - affectively toned 221 - emotional 318 - regulation of 374 - suppression 383 Drooping of the shoulder 88 Duct/Ductus -[duct] cochlear 148, 150,366 --floor 150 - [duct]endolymphatlc 148,152 -[duct] nasolacrimal 14, 21,122 - -opening In the orbit 15

--orifice 21 -(duct] parotid 92, 94,112 -(duct] perilymphatic 148 -(duct] semicircular 83, 140, 148, 152, 153, 368 --interactions on head turning 153 --location 148 -[duct] submandibular 106, 112 -[ductus] reuniens 148, 152 Dura mater 191, 196 -blood supply 1 90 -Innervation 190 --- meningeal 189, 254 -ofbrain 51,186,190,262 --relationship to inner ear 148 -of spinal cord 186, 191, 289, 344 --- periosteal 1 86, 189, 254, 262 Dural sinus see Sinus, dural venous Dysesthesia 218 Dysmetria 244 Dysostosis, cleidocranial 3

E Ear -external 140, 1 44 -inner 140,144,148,150,1S2 --decreased blood flow 149 --fluid 146,148 --functional disturbance, acute, unilateral 149 --projected onto the skull 148 -middle 140,144,146 --attic 147 --muscles, Innervation 74 --sound conduction to the Inner ear 151 -structure 141 E.ctoderm, surface 1 82 Efferent fibers 66, 232, 243, 280-283, 285 -of cranial nerves 78-89 -red nuclei 229 -subthalamic nuclei 225 -thalamicnuclei218, 219 Electroencephalogram 21 7 Emaciation 221 Embolism 264 Embryo, brain development 183 Eminence -cruciform 26 -medial, of rhomboid fosSil 227 Emissions, otoacoustic 367 Emmetropia 12S Emotion 375 -modulation 382 -neuroanatomy 382 Enamel 37 Encephalon see br;~in 172 Endbrain (telencephalon) see cerebrum Endocrine system 224 -function 210 Endolymph 148 -formation 1SO Endoneurium 180 -collagen fibers 176 Endoscopy, maxillary sinus 1 19

Fluid F

Endoplasmic reticulum, rough 174,222 Endothelium -capillary 197 - durahinuses 254 -sinus 189,254 Enophthalmos 349 Enteric neNOus system see Nervous system, enteric Enteroception 172 Entorhinal region 207, 375 Ependyma 192,195 Ependymal cells, function 177 Ependymal organs 196 Epiconus syndrome 356 Epidural anesthesia 291 Epidural hematoma 1 91 Epiglottis 102, 104, 110 -In coronal section 159 -In sagittal section 166 -innervation 86 Epilepsy 383 Epinephrine, In blood pressure regulation 325 Epineurium 1 80 Epiphysis see Gland, pineal Epistaxis see Nosebleed Epithalamus 183, 193,210, 214, 224 -function 214 -location 224 Epithelial cells, kinaciliated 118 Epithelium -cells, klnocrlrated 1 18 -ciliated 21,114,118 -- pharyngotympanlc tube 145 -oflens 127 -pigment -- of ciliary body 124 --retinal 131 -squamous, oral cavity 102 Epitympanic recess 147 Epitympanum 147 Equator -ofeyeball 125 -oflens 127 Erb brachial plexus paralysis 349 Erb-Chancot-StrOmpell disease 354 Erogenous zones, afferents to hypothalamus 221 Esophagus, Head zone 323 Ethmoid bulla 27,114 Ethmoid cells 5, 1 6, 1 8, 20, 27, 51,114,118 -coronal section 1 56, 158 -drainage of secretions 1 18 -sagittal section 167 -transverse section 160 Ethmoid sinusitis in children 20 Exocytosls, neurotransmitter release by 175 Expiration, nuclear region 230 Extensors see Muscles, extensor Exteroception 172, 179 Extrapyramidal motor system 229, 282, 340, 342 Eye -anterior 124, 126, 128 -chambers of -color 128 -conjugate 364 -- loss of 365 -coordination 364

- light refraction 125 -movements -parasympathetic effects 317 - posterior 124, 1 26, 1 28 -red 121 - reference lines 125 - refractive media 126 - surface anatomy 121 - sympathetic effects 317 Eyeball 124, 136 - blood supply 132 -[equator (meridian) 125] Eyebrow 121 -muscles 47 Eyelid 121 Eye socket see Orbit

F Face 92 - blood supply 92, 94 - emergence of nerve branches 93 - Innervation 92, 94 - spread of infection 65, 93 -triangular danger zone g3 -vascular relationships 65, 94 Fascia, bulbar 136 Facial furuncle 93 Facial sensation, disturbance of 75 Facial skeleton 4, 5 -bones 3 - sagittal section 166 Falx -cere belli 164, 188 - cerebri 8, 51, 187, 188, 254 --coronal section 157, 158 --transverse section 161, 162 Far-sightedness (hypropln) 125 Fascia -cervical 163. 168 - dentate 206, 375 - parotid 142 Fasciculus - [fasciculus] cuneatus 179, 233, 269. 276, 278, 284 - -axon, descending 277 - -central connections 277 --In cross section of medulla oblongata 237 - -somatotopic organization 276 - [fasciculus] frontotemporal 208 - [fasciculus]9racilis 179, 233, 169, 276, 284 - -axon, descending 277 - -central connections 277 - -In cross section of medulla oblongata 237 - -somatotopic organization 276 - [fasciculus] Interfascicular 268, 277 - [fasciculus] lateral 225, 268, 269 - [fasciculus] longitudinal - -dorsal 221 - --connections 321 --Inferior 377 - - medial 232, 364, 368 - --course in brainstem 365 - --in cross section of medulla oblongata 236 - --In cross section of midbrain 234 - --In cross section of pons 234

--- lesion 365 --- rostral Interstitial nucleus 364 --superior 208, 377. 381 -[fasciculus] mammillothalamic 215, 218, 219, 221 -[fasciculus] occipitofrontal 377 -[fasciculus] orbltofrontal 377 -[fasciculus] propriier 268, 273 --lateral 268 -[fasciculus] septomarginal 268, 277 -[fasciculus] strlatonlgral 229 -[fasciculus] sulcomarglnal 268 -[fasciculus] thalamic 225 -[fasciculus] uncinate 368,377 -[fasciculus] vertical occipital 377 Fat -In epidural space 290 - retro-orbltal 138, 156, 160, 162, 169 Fat pad -buccal 158, 163 -orbital [fat]136, 138 -- In coronal section 156 -- in sagittal section 169 --in transverse section 160, 162 -Buccal 158, 1 63 Fauces (throat) 102 Feedback, sensorimotor 336 Fetus. brain development 183 Fiber 342 Flber(s) - Ad myelinated 332 - annulosplral 273, 342 - arc:uate of cerebrum 208, 377 -association 208, 376 --interhemispheric 376 --long 377 --of teloncephalon 377 --short 377 -c 332 --unmyelinated 376 - cerebella-olivary 243 - dngulohlppocampal 374 - drc:ular 37 -dlmblng 241 -commissural 304, 376 - cortlcomesencephallc 232 - cortlconlgnl 229 - cortlconudear 79, 88, 232, 365 --In transverse brain section 234 -- ofintemal capsule 377 - cortlcoretlcular 280, 338 -corticospinal 232, 280, 338 --In transverse brain section 234 -- oflntemal capsule 377 - Cllneocerebellar 243, 278, 326 - decuuatlng intenlental 37 - frontopontlne 243 - Golgl 273, 342 -gustatory 78, 81,107,236,370 --chorda tympani 370 --nerve 370 -Ia 279, 328, 342 -lb 342 -lens 126 -mossy 241 -- trigeminocerebellar 243 - nigropalllclal 225 - olmctory 70, 1 1 6, 372 -pain 317 --myelinated 332 --non myelinated 332

-- parasympathetic 322 --sympathetic 322 - pallldosubthalamlc 225 - par•llel, cerebellar cortex 241 -parasympathetic, preganglionic, of bronchial wall 325 - parletopontlne, In transverse brain section 234 -pontocerebellar 233, 243 - proJection --ascending 376 --descending 376 - Relssner 196 - retrculo-ollvary 229 - netlculothalamlc 333 - nubro-ollvary 229 -somatic efferent 323 -sympathetic, postganglionic 325 - temporopontlne 234, 243 - vestibulocerebellar 368 -visceral afferent, reflex arc 323 -zonular 124,126,128 Fiber quality, functional, of nerve 66 Fibroma, nasopharyngeal 1 7 Filum terminale 288, 290 Fimbria of hippocampus 193,206, 296, 311.375 Finger-nose test 245 First motoneuron 354 Fissure

-cerebellar, longitudinal 184, 1 99, 292, 304 -hippocampal 375 -- horizontal, of cerebellum 238, 240,297,311,312 -of medulla oblongata 227 -of spinal cord 269, 281 -oribltal --Inferior 11, 14, 16, 29, 76, 100.134,138 ---in coronal section 157 ---In transverse section 162 ---transmitted structures 1 01 --superior 14, 16, 24, 29, 72, 76, 134,138 ---transmitted structures 90 -palpebral -- mimetic muscles 46 --width of 121 -petrotympanic 23, 32, 78, 80 --transmitted structures 90 - prebiventral 240 -primary, cerebellar 239, 240, 302,311,313 - pterygomaxlllary 17, 100 -tympanomastoid 23 Fisb.Jia, ilrteriovenous, intra-

medullary 289 Fixed pupil 1 28 Flechslg -oval area 277, 326 -tract 326 Aexors see Muscles, flexor Aexure -era nlal, embryonic 183 -cervical, embryonic 183 Aocculus 83.238.297.311 Auid -balance, regulation of 196 -cerebrospinal 186, 192 --absorption 254

395

F Fluid

--cerebral ventricles 192, 194, 196 --circulation 194 --cross section of medulla oblongata 237 --function 197 --hemorrhage, cerebrospinal fluid examination 197 --increase 7 --laboratory values 197 --leakage after head trauma 70 --production, dally 194 --sampling 197, 291 --spaces 192 --subarachnoid space 192, 194, 196 --subarachnoid 196 --ventricular 196 --volume 194 -lacrimal 123 Folia, cerebellar 240 -arborization 240 Foliate papilla 104,371 Folium (folia) -of cerebellum (cerebellar gyri) 240 -of vermis 238 Follicle-stimulating hormone 223 Follltnopln 223 Fontanelle 7 Food intake, autonomic center for coordinating 230 -regulation of 221 Foodway 102 Foramen (foramina) - anterfor sacral 321 - cewm 40, 1 04 -ethmoidal 14, 27 -Incisive 6, 11, 29, 103 - Infraorbital 2, 4, 15, 77, 93, 120,122 -lnterventrtwlar 187,192,194, 305,315 --in transverse brain section 306 --Internal cerebral vein 260 - Intervertebral 191, 290, 345 - jugul•r 11, 13, 62, 84. 86. 88. 255 - lacerum 11, 13, 80 --topographic relationships 1 0 -magnum 10, 12, 26, 88, 189 --herniation of cerebellar tonsils 189 --sagittal section 166 --venous plexus 65 - mandibular 30, 77 - mastoid 6, 11, 23, 257 - mental 2, 4, 30, 77, 93 - oc;dplt•l 257 -of Monro see For11men. interventrlcular -ovale 11,13,17,25, 77,99 -palatine --greater 11, 17, 2g, 103 --lesser 11,29,103 - parietal 8, 257 - rotundum 15, 17, 24, 29, 76 -sphenopalatine 17 --transmitted structures 1 01 -splnosum 11,13,17,24,190 -stylomastoid 11, 13, 23, 78, 80, 99,109 -transmitted strudures 90, 101

396

-supraorbital 2, 4, 14, 77, 93, 120 - zygomatico-orbital 15 Force sense 284, 328 Forceps -anterior 305, 377 -frontal 305 -occipital 305 -posterior 305, 306, 307, 377 Forebrain 183 -bundle, medial 221, 372,375 -vesicle 211 Forel axis 185, 198 Forel's field 225 Fornix 192, 199,204,210, 212, 214, 220, 309, 374, 376 -caudal part 206 -conjunctival 121 -In coronal brain section 294, 297 -In midsagittal section 195 -in sagittal brain section 315 -in transverse brain section 305 -phylogenetic origin 199 -topography 205 Fossa - cerebellar 13 -cerebral 13 -cranial --anterior 12, 16, 19, 138, 166, 187,190 -- -coronal section 156 -- -sagittal section 166 -- -sites for passage of neurovascular structures 90 -- middle 12, 16, 19, 138, 159, 187,190 -- -coronal section 15 -- - relationship to tympanic cavity 145 -- -sites for passage of neurovascular structures 90 ---veins 64 -- posterior 12, 187, 190 -- - meningeal innervation 86 -- -sites for passage of neurovascular structures 90 -hyaloid 124 -hypophyseal 13, 19, 20,21, 24,25 -Infratemporal 17, 98, 157, 160, 162 -lnterpedunwlar 161,213,227 -Jugular 23 -mandibular 11, 22, 32 -- panoramic tomogram 39 -of lacrimal gland 122 -of lacrimal sac 15 - pterygoid 24, 29, 48 -pterygop.~~latlne 15, 17,100. 117 -- adjacent structures 17 -- boundaries 17, 1 00 --nerves 17,101 -- routes of approach 17 --vessels 17,100 -rhomboid 226, 298 -- In coronal section 198, 299 -- In cross section of medulla oblongata 236 - scaphoid 141 -temporal 48 - tonsillar 11 0 -triangular 141 Fovea

- centra lis 124, 130, 359 -pterygoid 30 Foveolae, granular 8, 186, 189, 254 Fracture 5

- LeFort lines 5 - [fracture! mldfaclal 5 - [fracture! pyramid 5 - [fracture! skull, basal 12 Frenulum -of lip 102 -of tongue 106 FSH (follicle stimulating hormone) 223 Functional fiber quality, of nerve 66 Fundus, optic 133 Funiculus - anterior, of spinal cord 268 - cunneatus 236, 276, 284 - gracilis 236, 276, 284 - lateral, of spinal cord 268 -posterolateral 319 - posterior, of spinal cord 233, 268 - - T8, lesion of 353 Furrow see Sulcus

c GADA (gamma-aminobutyric acid) 241 Gag reflex, trigger zone 1 96 Galt ataxia 244, 245 Galea aponeurotica 44, 189. 254 Gallbladder, Head zone 323 Gamma motor neuron 281, 328 Ganglion (ganglia) -autonomic 69, 180 -basal - -blood supply 251 - -disease 337, 340 - -hypertensive hemorrhage 263 - -In programming movements 336.340 - -infarction, symmetrical 265 - -lesion 225 --motor loop 341 - -projection onto the brain surface 208 --Melbomlam 121,123 -cellae 316 - cervtcal 316 - -Inferior (stellate ganglion) 316,349 --middle 316 --superior 122, 224,316, 34g - ciliary 69, 72, 76, 137, 139, 362 - -lesion 363 - cochiNr 150 - connecmd to the cnnlal nerves 69 -geniculate 69, 78, 80, 109, 145, 149 - -gustatory pathway 370 - Intramural 180 -Jugular 69, 86, 322 -mesenteric 316 - near organ• 320 - nodosum 69, 86, 322, 370 -of spinal nerve - otic 69, 84, 99

--communicating branch witf1 auriculotemporal nerve 99 - p.rasympathetlc 316, 318, 320 --nearorgans 316 - p - a l 69, 84, 370 - prevertebral 316, 322 -pterygopalatine 15, 17, 69, 78, 80,95,101,116 --postganglionic fibers 320 --preganglionic fibers 320 -sacral 321 -sensory 69 -spinal 180, 266, 274, 276, 290, 317' 322, 332, 344 --lesion of 352 --neuron, primary afferent 175 --perikaryon, pseudounipolar 273 -- T6, lesion of 352 -spiral, of cochlea 69, 82, 149, 366 -stellate 316, 349 -submandibular 69, 78, 81, 106, 109 -sympathetic 318,322 --nearorgans 316 -trigeminal 69, 76, 80, 95, 99, 109,117,137,334 --In sagittal section 168 - vestlbublr 69, 82, 149, 155 --Inferior 83, 149, 152 --superior 83. 149, 152 Ganglion cells, retinal 131, 363 Gastric juice, secnetlon of 225 Gaze - center(s) 364, 365 -movements 364 Genital function, tract for 283 Genu -of corpus callosum 205, 377 --In sagittal brain section 314 --in transverse brain section 305 - offacial nerve --internal 78, 228 --external 80 -of Internal capsule 377 --in coronal brain section 294 --in sagittal brain section 313 --in transverse brain section 305 Gennari, stria of 203, 358 GH (growth hormone, somatatropin) 223 Gingiva 37 -innervation. sensory 103 Gingiva (gum) 37 Gingival margin 37 Glabella 18 Ciblnd(s) - •nterlor lingual 106 -bronchial stimulation -- parasympatf1etlc 325 --sympathetic 325 -cerumen 143 -Ebner 104 -ICrau•e 122 -labial 113 -lacrtmal120, 122,137,161 --accessory 122 --Innervation 76, 78, 81 --- parasympathetic 122 ---sympathetic 122 --orbital 120, 122 --palpebral 120, 122 --punctum 122

Hom

--sac 120,122 -Moll121 - naHI,lnneNiltlon 81 - palatine 113 -parotid 92, 112, 142 --accessory 112 --deep 113 --excretory duct 92, 94, 1 12 --facial nerve 94, 1 13 -- in coronal section 51 -- in transverse section 164 -- Innervation 85, 320 -- superficial 113 - pharyngul 113 -pineal (pineal body) 183, 192, 196, 210,212,214,224, 227, 297,308,315 -- arterial supply 250 -- caldflcatlon 224 --failure during childhood 224 --function 300 -- in coronal brain section 299, 300 -- retinal afferents 224 -- structure 224 -pituitary 16, 21. 183, 184, 187, 192, 222, 226, 315 --anterior lobe 210, 220, 22 -- connections -- -with hypothyroidism 221 -- -with hypothalamic nuclei 222 -- coronal section 159 -- control of hormones, hype>thalamic 223 -- divisions 222 -- histology 223 -- hormone release 220, 222 -- pars tuberalls 222 -- primerdlum 153 -- posterior lobe 196, 210, 220, 222 -- sagittill section 166 --transverse section 161 -salivary 317 -- Innervation 112 --large 112 --major 112 --small113 - sebaCIIOUS 143 -seromucous 371 -subllngu~l 112 -- bimanual examination 113 -- innervation 78, 81, 320 -submandibular 51, 112, 168 -- bimanual examination 113 -- Innervation 78, 81, 320 -tarsal 121 -turbinate, innervation 320 - Wolfrlng 122 Glandotroplc hormones 223 Glaucoma 129 -angle-closure 129 - attilck 128 Glial cells, function 177 Globuspallidus 198,211,215, 224,338 -extern us 218 -hemorrhage 263 -in transverse brain section 306, 307 -lnternus 218 -In coronal brain section 294, 296

-lateral segment 215, 218, 219, 224,294,296,307,311 -medial segment 167,215,218, 219,224,294,307,312 -motor loop 341 Glomerulus, olfactory 373 Glucose transport to the brain 197 Glutamate 370 Glycine 273 Goblet cells - conjunctival, distribution 123 - nasal mucosa 1 1 8 Goldmann tests 196 Golgi apparatus 174 Golgi cells 241 Golgi method 200, 231 Golgi tendon organ 179, 328 Gradenlgo syndrome 145 Granule cells 241 - definition 201 - dentilte gyrus 375 - olfactory bulb 373 Granulations - arachnoid 186, 194 - Pilcchlonliln 186, 189, 194, 254 Grily matter see Substilntiil/Matter, gray Groove see Sulcus Growth hormone (somatotropin) 223 Gustiltory cells 371 Gustiltory pathway 370 Gyrus (Gyt1) -ambient 70 - -olfactory pathway 372 -angular 381 - cerebral 184 - clngulate 206, 218, 221, 31 5, 374, 379, 382 - -connections with thalamus 218 - - frontill, lesion 383 - -in coronal brain section 292, 294,296 - dentate 205, 375 - -In coronal brain section 297 --in sagittill brain section 168. 311 - -in transverse brain section 307 - faKlolar 206 - Heschl 366 - Umble see Gyrus, clngulate - p•r•hlppocampal 206, 374 - -in coronal brain section 293 - -in sagittill brain section 31 0 - paratermlnal 374 - postcentral 184, 218, 275, 277, 326, 329, 333, 336, 370 - - blood supply 251 - -cortex 200 - - projections from thalamus 218 - precentral 79, 184, 218, 294, 336 - - blood supply 251 - -skeletal muscle representation, somatotopic 339 - semilunar 70, 373 - -olfactory pathway 372 -transverse tempor~l 366

H Habenula 21 2, 224, 225 -in coronal brain section 298 Hair cells -Inner 150, 366 -outer 150, 367 Hair follicle receptor 328 Hamulus, pterygoid 17, 25,103 Head position, adjusting to compensate for oculomotor palsy 135 Head zones 323 Head

-section --coronal muscle(s) 156, 158 --Innervation, sensory 95 --nerves, superficial, lateral 94 -- pilln pilthWilYS 124, 334 -- rotiltion 1 52 --- interaction of semicircular ducts 153 ---saglttill 166,168 --sensory system 217 --- trilnsverse 160, 162, 164 --venous drainage 63 --vessels, superficial, lateral 94 Headache 190 Hearing -acute 252 -acute, unilateral 149 -cause 140 -loss 80, 82 -- sensorlneural149, 252 -temporary 143 Heart - Head zone 323 - parasympathetic effects 317 -sympathetic effects 317 Heat - receptors 328 -sensation 179 Helicotrema 148, 1 SO Helix 141 Hematoma -epidural 59, 189, 191 , 262 -large 263 -subdural 191, 262 Hemianopia - bitemporal 360 -contralateral 265 - homonymous 360 Hemiballism 225 Hemiparesis, Wernicke-Mann type of 265 Hemiplegia -spastic 343 -spinal 355 Hemisensory deficit 265 Hemisphere 184 -asymmetry 381 -cerebellar 238 -cerebral --parts 198 --surface contours 199 -dominance 380 -of cerebellum 238 Hemorrhage -epidural 189 -into the CSF space, CSF examination 197 -Intracranial 262 --extracerebral 262

H

-- intracerebral 263 -- lesion of optic radiation 360 -subarachnoid 191, 262 -subdural 188, 1 91, 262 Herniation

-intracranial 189 -ofbraln 189 -of Intervertebral disk 345 Hiatus - maxillary 15 -of canal for greater petrosal nerve 80 --transmitted structures 90 -of canal for lesser petrosal nerve, transmitted structures 90 -sacral 291 -semilunar 27 High-pass filter 147 Hillock, axonal 1 74 HlppoCilmpus 193,204, 206, 215, 221. 309,374,379, 382 -arterial supply 250 - atrophy 383 -changes In Alzheimer's disease 383 -connections 375 --with hypothalamus 221 -contralateral 205 -cytoarchitecture 375 -cytoarchitecture 375 -foot 299 --sec:tion ---coronal 295 ---saglttill 169 ---transverse 309 -function 206 -in coronal brain section 296 -in transverse brain section 308 -lesion 206 -proper 206, 375 - retrocommlssural 375 -topography 205 Hoarseness 86 Homunculus -motor 217,339 -sensory 329 Hormone(s) 222, 223 - pituitilry (anterior pituitary hormones) 223 Horn -[hornJAmmon's 206,207, 375 -- phylogenetic origin 199 -[horn I greater, of hyoid bone 31 -[hornJiesser,ofhyoid bone 31 - [hornJ anterior, of lateral ventricle 187, 192 --sections ---coronal 292, 294 ---sagittill 312 - [hornJiateral, of spinal cord 266, 269 - [hornJ occipital, of lateral ventricle 160,187,192,205, 296.299 --sections ---coronal 302 ---saglttill 311 ---transverse 305, 306, 308 -[horn I temporal, of lateral ventricle 187,192,205,207, 296, 299, 375 --sections -- In coronal brain section 293, 294

397

H Hom

---saglttal310 --- transverse 309 Horn -anterior see Spinal cord - lateral see Spinal cord - posterior see Spinal cord - lesion see Lesion, hom Horner syndrome 128 - unilateral 349 Hydrocephalus 7 - internal 1 92 Hyperacusls 80 Hypermetrla 244 Hyperopia (far-sightedness) 125 Hypertension, and rupture of a cerebral artery 263 Hyperdlermia, central 221 Hypoesthesla 355 - unilateral 330 Hypopharynx, sagittal section 1 67 Hypophysis see Gland, pituitary Hypothalamic region, function 221 Hypothalamus 183, 193, 210, 214,220,283,315,318 -afferent connections 221 - aut:Dnomic information 221 -connections --with medial dlalamlc nuclei 219 --with reticular formation 221 -efferent connections 221 -function 214, 220 - nuclei 222, 223 --groups 220 - In coronal brilln section 294 - (hypothalamus) lateral 220 -lesion 383 - location 220 - (hypothalamus) medial 220 - pain Impulses 333 Hypothermia 221 Hypotympanum 147 Hypoxia, cerebral 375

ICSH (interstitial cell-stimulating hormone) 223 Impedance matching 146 Implant, cochlear 366 Impulses. afferent 204 Incisors see Teeth Incisure/Notch -!Incisure] frontal 4, 14 -]lnclsure]lntertraglc 141 -lincisure]tentorial 1 88 -lincisure]tympanic 143 -!notch] mandibular 30 -!notch] mastoid 11,23 - ]notch] supraorbital 77 Incus 143. 144, 14(i -articular surface for malleus 146 Indusium grise urn 204, 206, 374 - phylogenetic origin 199 Infarction, cerebral -cerebral venous occlusion 265 -disturbance of sensory perception 216 - hemorrhagic 263 - middle cerebral artery 264 -small 263

398

-territorial 264 - dlalamlc, symmetrical 265 Infection, spread, In facial region 65,93 Information

-cerebral see Cerebral infarction -processing -- cortical area 200 -- sensory 329 -transmission from the cerebral cortex, cortical areas 200 Infraorbital margin 4 Infundibulum -ethmoid 27,118 -of pituitary gland (pituitary stalk) 21 0. 212, 215, 222, 315 Inhibition, recurrent 271, 273

Inner ear see Earl inner Innervation -bronchial 325 -cutaneous - - retro;mricular 86 --segmental 267 -Intestinal 324 -of organs 316 -of the trunk, radicular 345 -radicular, projected onto the skin 344 -tracheal, autonomic 325 Input, afferent 241 Inspiration, nuclear region 230 Insula 184,198 -arterial supply 250 -arteries 249 - development 183 -In coronal brilln section 293, 296 -in sagittal brain section 31 0 -in transverse brain section 306, 308 -phylogenetic origin 1 99 Insular cortex see Cortex. Insular Insular region 307 Integration, sensorimotor 181 Intention tremor 244, 245 Interbrain see Diencephalon Intercalated cells 271, 273 lnterneuron(s) 175, 181, 268, 271' 283, 342 -inhibitory 273 -- cerebellum 241 -motor 181 -polysynaptic reflex arc 272 -pyramidal tract 281 -retinal 131 Interstitial cell-stimulation hormone 223 lnterthalamlc adhesion 192, 21 0, 212 Intervertebral disk 345 Intestinal motility, effect of opiiltes on 324 Intestinal wall, 1 80 Intestine -large. head zone 323 -small -- Head zone 323 -- nervous system, enteric 324 Intrinsic cells 271 Iris 121,124, 128 -blood supply 132 -epithelium 129 -stroma 129 -structure 129 Ischemia

- cerebral 247, 264, 286 - -cardinal symptoms 265 - - causes 264 - spinal cord 286 Isocortex 198 -Alzheimer's disease 382 -layers 375 Isthmus, faucial 1 02

jacksonian seizure 330 Jet lag 224 Joint receptors 179, 327 Joint - lncudomalleolar 146 -lncudostapedlal 146 - median atlantoaxial - -sagittal section 166 --transverse section 165 -temporomandibular 32, 34, 50 - -articular disk 33, 35, 45, 50 - -biomechanics 34 - -guide muscle SO - -ligaments 32 - -joint capsule 32, 35, 49 - --sensory supply 33 - -movements 34 - -relationship to external auditory canal 143 JugumOuga) - alveolarla 30 - sphenoldale 12, 25

K Kidney, Head zone 323 Kinocilium 118, 1 52 Korsakoff syndrome 220

L Labial creases 102 Labyrinth - blood supply 155 -bony 148 -cochlear 148 - membrilnous 148

--innervation 149 -vestibular 148 Lacrimal apparatus 1 22 Lamina/Layer -!lamina] ;rifixa 212 -llamina]cribrosa,ofsclera 124, 131 -!lamina] limiting, of cornea 127 - [lamina] medullary, of thalamus 215.217 -!lamina] orbital, of ethmoid bone (lamina papyracea) 1 6, 21, 27,156 -!lamina] papyracea 16, 21, 27, 156 -!lamina] Rexed 217,332 -!lamina] spiral 150 -!lamina] tectl see Plate, quadrlgemlnal - !lamina] termlnalls 205

--vascular oyon 196 -!lamina] vltrea, of calvarium 9 - llamlnil] white matter fibers 225 - !layer] choroidocapillary 132 -Ilayer] ganglionic, of cerebellar cortex 241 -Ilayer] granular, of cerebellar cortex 241 - Ilayer] molecular, of cerebellar cortex 241 -Ilayer] neural, of retina 124 -Ilayer] pigmented, of retina 124 -Ilayer] Purldnje, of cerebellar cortex 241 - !layer] granular 200 -- cerebellarcortex 241 --visual cortex 203 -!layer] molecular 200 -!layer] multiform 200 - !layer] pyramidal 200 - !layer] retinal 124, 1 30 Lacrimation, disturbance of 80 Lacuna, lateral 186, 189,254 Language deftclt (aphasia) 251 Laryngopharynx 1 02 -coronal section 1 59 lateral sclerosis, amyotrophic 354 Layer see Lamina Learning 374, 379 LeFort fracture line 5 Lemniscus -lateral 233. 275, 366 --in cross section of pons 234 -medial 218, 233, 236, 275, 277, 326,329 --In cross section of pons 234 --in sagittal brain section 313 --in transverse brain section 234 --lesion 21 8, 330 -spinal 233,275, 331 -trigeminal 217,331 --lesion 330 Lens 121,124,126,127,128,132 -capsule 127 --posterior, vitreous attachment to 125 - silglttal section 1 69 -transverse section 161 Lens, crystalline see Lens Leptomeninges (pia mater and arachnoid) 186 Leslon(s) - atherosderollc 247 -bilateral, of mammillary bodies 220 -brain, disinhibition of rage, suppression of drive 383 -cerebellar 244, 245, 337 -conus 356 -cord, complete 356 -horn 352, 354 --anterior 354 ---C:7-C8 354 --posterior 330 --- C:5/C6/C7/C:8 352 -of bralnstem 226 -of centnl motor pathway 343 -of cerebral peduncle (crura cerebrl) 343 - ofcortex 343 -of gray matter 353 -of hippocampus 206 -of hypothalamus 221

Melanin M

-- anterior preoptic region, central hyperthermia 221 -- posterior region, hypothermia 221 -- supraoptic nuclei, hyponatremla 221 - of Internal capsule 343 -of mammillary bodies 220 -of medl•llemniKus 21 8 -of motor neuron, second 354 -of motor tract 343 -of...nerve --facial 80 -- glossopharyngeal 84 --gluteal, superior 351 -- hypoglossal 89, 1OS -- hypothalamic 383 -- laryngeal 87 -- optic 208, 360 -- - unilateral 363 -- vestibulocochlear 82 -of... neuron -- motor, second 354 --red 229 -- splnal75, 330 - of•••nucleus --hypothalamic 221 -- of ventral posterolateral nucleus of thalamus 218 --red 229 -- subthalamic 225 --thalamic 218 --ventral posterolateral (VPL) 218 - of occipital lobe 360 -of optic chl•sm 360 -of pons 343 -of posterior funiculus 353 --tract 330 -of sacral plexus 351 - of sensory system 330 -of spin•I cord 289 -of spinocerebellar tract 355 -of TB posterior funiculus 353 -of thalamus 216 -optic 360 -punched-out, in skull9 -root 346, 352, 347 -- dorsal 330, 345, 352 -- -C4-T6 352 -- -clinical signs 347 -- - dermatomes 346 -- L3\L4\L5 347 --S1 347 --ventral 345, 346 -- -clinical signs 347 -- -Indicator muscles 346 - splnothahlmlc 330, 353 -thahlmlc 216 LH (luteinizing hormone) 223 Uberln 223 Lid closure 47 Ligament -annular stapedial 146 -denticulate 191,290 -lateral malleolar 147 -lateral, of temporomandibular ]oint 32,49 -nuchal, sagittal section 166 -palpebral 120 -periodontal 37 -posterior longitudinal 289, 345 - pterygosplnous 33 -sphenomandibular 33

-spiral 150 - stylomandibular 32 -transverse, of atlas - -sagittal section 166 --transverse section 165 -Wieger 125 Light refraction 125 Light response, pupillary 363 Limbicsystem 204,206,219,221, 299, 318, 372, 374, 379 -Alzheimer disease 382 -function 374 - Inner arc 374 -lesion 383 - outer arc 374 - pain impulses 333 - Papez circuit 374 - projection fibers 376 Limbus 204 - of bony spiral lamina 150 - of cornea 124 -spiral 150 Limen -nasi 115 -of insula 311 Line, oblique 30 Lingula of cerebellum 238 -in sagittalsection 315 Llp(s) 102 -upper 102 - -innervation, sensory 1 03 Liver, Head zone 323 Lobe(s)/Lobule(s) -aurtcular,ofearlobe 141 - cenebellar --[lobe] anterior 238 - --coronal section 297. 298 - --deficit symptoms 244 - --sagittal section 311, 314 --[lobe] flocculonodular 238, 368 - --deficit symptoms 244 --[lobe] posterior 238 - --coronal section 298, 302 - --deficit symptoms 244 - --sagittal section 311 - --transverse section 163 - - [lobuleJ central 238, 240 - - [lobuleJ quadrangular 238 - - [lobuleJsimple 238 - - [lobuleJ superior semilunar 238 - cenebr•l --[lobe] frontal 51, 57, 70, 156, 157, 158,184,187,192, 198, 199, 21 9, 249, 304, 310 - --connection with medial thalamic nuclei 219 ---coronal section 51. 156. 158 - --transverse section 304 - --syndrome 21 9 - --connection with mldeal thalamic nuclei 219 - --coronal section 51. 156. 158 - --transverse section 304 --[lobe] insular 184, 198, 199, 249, 250,293,294,307,310 -- [lobe]llmblc 199 --[lobe] occipital 163, 184, 192, 198, 199, 260, 304, 305, 306, 310 - --association area, connections with thalamus 219 - --transverse section 163, 304

--- lesion, Involving optic radiation 360 --[lobe] parietal 159, 184, 198, 199,210,219,249 --[lobe]temporal 51,57, 114, 159,184,187,189,192,193, 198,199,207,249,260 ---coronal section 51, 159 --- infarction 265 --- medial, bilateral lesions 383 --- mesiobasal 189 ---coronal section 51, 159 --- Infarction 265 --- medial bilateral, lesions 383 --- mesiobasal 189 - insular 184, 199 -limbic 199 -pituitary --[lobe] anterior (adenohypophysis) 210, 220,222,233 see also Gland, pituitary --[lobe] posterior (neun> hypophysis) 196, 210, 220, 222 Locus (Loci) - ceruleus 230, 379 --in c:ro.ss sec:tion of pons 234 Loop, Meyer 358 -lesion 360 Loop, motor 285, 341 LTH (luteotropic hormone) 223 Lumbago 345 Lumbar puncture 197,267,291 Lung - parasympathetic effects 317 - sympathetic effects 31 7 Luteinizing hormone 223 Luteotropic hormone (lutropin) 223 Lymph follicle, oral cavity 111 Lymph nodes 107,113,142 -cervical 107. 142 - intraparotid 113 -jugular 1 07, 113 - mastoid 142 - parotid 142 -submandibular 1 07. 113 -submental 107 Lysozyme 112

M Macula - lutea ("yellow spot") 130 --structure 131 -of saccule 148,368 --orientation of stereocilia 153 --structure 152 -of utricle 148, 368 --orientation of stereocilia 153 --structure 152 -utricular and saccular 152 --orientation of stereocilia 153 Macular degeneration 133 Magnetic resonance Imaging, functional, for mapping brain activity 379 Mallear prominence 143, 147 Malleus (hammer) 144, 146 -head 146 - menubrlum 146, 155 Mallholer fold, superior 149

MALT (mucosa-associated lymphatic tissue) 111 Mammotroplc hormone 223 Mandible 2, 3, 4, 6, 30, 166 -alveolar process 30 -- resorption of 31 -age-related changes 31 -grinding movements 48 -head 30,32 --articular surface 50 - - axis of rotation 34 --In transverse section 163 -laterotruslon 34 - medlotruslon 34 -protrusion 34.48 -retrusion 34, 48 Mandibular teeth see Teeth Mantle cells (satellite cells), function 177 Manubrium of malleus 146, 155 Martegiani ring 125 Mask-like facies 229 Mass, intracranial 262 -unilateral 189 Mastication 225 Mastoid aircells 22, 109, 144 Matter see Substantia/Matter Maxilla 2, 4, 6, 10 -nasal septum 18 -orbit 14 -orbital surface 15 -palatine process -palate, hard 28 -sagittal section 167 -transverse section 165 Maxillary sinus-ethmoid ostium, ostiomeatal unit 118 Maxillary teeth see Teeth Meatus -acoustic --external (external auditory canal) 23. 32.140,142,144, 147 ---bony 143 ---cartilaginous 143 ---transverse section 164 --Internal 80, 149 -nasal19,21,114,145 -- coronahection 156 --superior 19, 21, 27,115,145 Mechanoreceptors 179 Medulla oblongata 184, 185, 226, 227,236, 237,318 -blood vessels 252. 253 -damage due to intracranial pressure 189, 197 -development 183 -location 213 -motor function 338 -nerves 66, 67, 72, 82-86, 88, 89, 91 see also Nerves, cranial -neurons, sympathoexcltatory 319 -nuclei 228. 276 see also Nuclei, of cranial nerve -projection onto skull 187 -sections --coronal 297 --(mid)sagittal314,315 --transverse 164, 229, 236, 237, 253,333 -tracts 276, 280 Medullary sheath 1 76 Melanin 229

399

M Melanocytes

Melanocytes, Iris 129 Melanotropln alpha/beta 223 Melatonin 224 Membrane -arachnoid 186, 188, 191 --of brain 262 --of spinal cord 191, 290 -basilar 150 -Bruch 131 - Descemet 127 - hyaloids 9 - limiting, glial 189 - limiting, of retina 131 -otolithic 152 -postsynaptic 175 -potential 174 - presynaptic 175 - Relssner 150 -Shrapnel(slc]143 -stapedii!I 146 -tectorial 150, 366 -tympanic (eardrum) 22, 140, 143,144,146,151,155 --coneofllght 143 --parameters --- flaccida 143 --- tensa 143 --resistance of 367 --sound reception 151 --umbo 143,147 --vascular supply 155 Memory (memories) 205 - limbic system 374, 379 - Impairment 220 -organization 205 - hippocampus 206 -short-term, impairment 206. 220 -stored 382 Meninges 172,186,188,190 -dura mater 51,186,190,262 - innervation 86. 190 - leptomeninges 186 - relationship to calvarium 189 -short term 206, 220 Meningitis 9, 1 DO, 120, 190 -after head trauma 70 -cerebrospinal fluid examination 197 - posttraumatic 13 -secondary to a facial furuncle 93 Mesencephalon (midbrain) 185, 215,219,226,275,315 - blood vessels 252, 253 -development 183 - nerves 66, 67 -parts 215,315 -roof 225 -sections --coronal 189,215 --(mid) sagittal 185, 21 0, 299, 313-315 --transverse 160, 199, 229, 234, 253. 308. 309. 319. 333. 335 -(midbrain] tectum 72, 183, 226, 229 Mesotympanum 147 Metathalamus 213, 216 Metencephalon 183 see also Cerebellum and Pons Meynert brainstem axis 185, 226 Mlcnocephaly 7 Microglia 176 Microglial cells 176

400

Micturition (urination), tract for 283 Midbrain see Mesencephalon Middle ear see Ear, middle Migraine attack 128 Miosis (pupillary contraction) 128, 329,362 Miotic agents 128 Mitochondrion 174 Mitral cells 373 -mixed 180 -motor, lesion 343 -peripheral 180 -- development 182 MLF see Fasciculus, longib.Jdinal, medial Modiolus 149 Modulating centers, subcortical 379 Modules, cortical 201, 328 Molars see Teeth Mononuclear phagocytic system 176 Motility, enteric 324 Motion sense 284, 326, 328 Motor control. somatic 210 Motorfunction -coordination, unconscious, tracts 278 -feedback loop 378 -fine control 369 -unconscious 281 -voluntary 184, 280 Motor neuron see Neuron, motor Motor support 369 Motor system 336 -cerebellar function 239 -lateral 282, 285 -medial 282, 285 -nuclear regions 340 Mouth - disorder 341 -closure of 48 -control, sensorimotor system 337 -movements of temporomandibular joint 35 -opening 48. 50. 108 Movement(s) -cerebellar function 244 -disorders 337, 340 -feedback loop 336, 378 -fine coordination 233, 239, -gait 229 -initiation 336 -- lmpelred 337 -programming 336 -purposeful 239 -- anatomical structures involved 336 -- cerebellar function 337 --function of basal nuclei 337 -uncoordinated 337 MRF (mesencephalic reticular formation) 364 MRI (Magnetic resonance imaging) 379 MSH (alpha/beta melanotropln) 223 Mucins,lacrimal fluid 123 Mucosa 118 -laryngeal Innervation 86 -nasal 118 -olfactory 70, 372

- palatal 103 - pharyngeal 86 Muller cells 131 Multiple sclerosis 177 - damage to association fibers 208 - Internuclear ophthalomoplegla 365 Muscle contraction, reflex 272 Muscle reflex 272 -loss of 346 Muscle spindle 179, 279, 327, 328 Muscle tone 217, 229,233,239, 245,369 - decreased 244 Muscle weakness 245, 346, 347, 350,351 - ventral root lesion 346 Musclefs) - abductor polllds brevis. spinal cord segments 357 - adduttor magnus, spinill cord segments 357 - -weakness 347 - adducton - -thigh, weakness 350 - -vocal cord. innervation 86 - antitragus 141 - aurtwlarls 45, 47, 141 -back 47 - -Intrinsic 52 - blap; brachll - -spinal cord segments 357 --weakness 346 - bnchloradlalls - -spinal cord segments 357 --weakness 346 - bualnator 44, 46. 47, 94. 98. 112 --coronal section 156,158 - -Innervation 95 - -sagittal section 169 --transverse section 165 - dllarls 72, 124, 126, 128 - -innervation 72, 127, 320 - - paralysis 72 - constrtctor pharyngls Inferior 168 - connugator superdlll 44, 46 --origin 52 - crtcoarytenold, posterior, innervatlon 86 - crtcothyrold, Innervation 86 -deltoid --weakness 346 - -spinal cord segments 357 -depressor - -anguli oris 44, 46, 52 - - labllinferioris 44, 46, 52 - - septi n;15i 52 - -supercilii 47,120 - dlgastrtc --belly --coronal section 156,158 --sagittal section 167. 168 ---anterior 51,108,157,158 - --- innervation 74, 95 - --posterior 53, 108 - --- Innervation 78, 95 --Intermediate tendon 108 - dilator pupillae 128 - -innervation, sympathetic 128 - dlst.11,1nnervatlon 282 - eplcranlus 45, 47 - extensor hallucls longus

--spinal cord segments 357 --weakness 347 -extensor --digital 346 --knee 350 --toe, paralysis 351 - extraoallar 79 -hdal 68 -flexor --hip, weakness 350 --- digital 346 --plantar 351 --thigh, weakness 347 -genioglossus 53, 105, 112 --coronal section 156, 158 --function in hypoglossal paralysis 89 --Innervation 89 --origin 52 --paralysis 1 05 --sagittal section 166, 168 -geniohyoid 105, 112 --coronal section 51, 156, 158 --origin 52 -gluteus --maxim us. weakness 347 --medius, weakness 347, 351 -- minimus, weakness 351 -hellcls 141 -Horner 46 -hyoglossus 53. 105. 112 --innervation 89 - hypodlenar, weakness 346 -Indicator 270, 346 - lnfrahyold 108 -Interossei, spinal cord segments 357 -laryngeal --cranial nerve nucleus 68 --Innervation 86, 88 -latissimus doni, spinal cord segments 357 -leg, innervation 282 -levator --anguli oris 44, 46 --- origin 52 ---transverse section 165 - -labii superioris 44, 46. 169 --- alaeque nasi 44, 46, 1 20 ----origin 52 --palpebrae superlor1s 120, 134, 136,138 --- coronal section 156 - - - innervation. motor 72 --- paralysis 72 - - - sagittal section 169 ---transverse section 160 --scapulae, sagittal section 169 -- veli palatini 1 03. 145 --- sagittal section 168 -longissimus capitis, Insertion 52 -longlb.Jdlnalls 105 -longus tapltls 53. 167 -masseter 44, 47, 48, 92, 94, 97,112 --coronal section 157 --function 48 --Innervation 48, 77, 95 --insertion 48, 52 --transverse section 163 --(masseter(deep 48,51,157 --(masseter( superficial 48, 51, 157

Nerve(s)

-- ortgln 48, 52 - mentalis 44, 46 -middle ear, Innervation 74 -mimetic 44, 46, 52, 92 --function 46 -- Innervation 78, 95 - multlsegmental 270, 272 -mylohyoid 108, 112 -- coronal section 51, 156, 158 -- innervation 74, 95 --origin 52 -- sagittal section 166, 168 -nasalis 44, 46, 120 -- laryngeal 52 --transverse 52 - nudlal, insertions 52 -nucteal 52 - obllquusJobllque -- [obliquusJ auriculae 141 -- [obliquusl capitis -- -inferior, sagittal section 167 -- -superior, insertion 52 -- [obliqueJinferlor, 73, 134, 136 -- -sagittal section 169 -- -transverse section 162 --[oblique] superior 120,125, 134,138 -- -coronal section 1 57 -- -Innervation 72 -- - paralysis, contralateral to trochlear nerve lesion 72 -- -transverse section 1 60 - ocdpltofl'ontalls 44, 47 --frontal belly 1 69 -of buttock, sympathetic effects 325 -of fadal expression 44-47 -of eye -- cranial nerve nuclei 68 --extraocular 134 -- -coronal section 1 56 -- -function 135 -- -innervation 72, 135 -- - paralysis 72, 135 -- Intrinsic 139 -- -Innervation 72 -- - paralysis 72 -of mandible (masseter, temporalls, and pterygoids) 48 -of mastication 44,48-51, 92 --coronalsectlon 51,156 -- cranial nerve nucleus 68 --deep 50 -- innervation 74, 95 -- insertions 48, 52 -- ortglns 48, 52 -- sling 48, 50 -- superficial 48 -of oral floor 102, 1 08. 156 -- innervation 74, 109 - of tongue 105 -- cranial nerve nucleus 69 -- Innervation 89 -- insertions 53 --origins 53 - orblaJialts 46, 52, 120 --oculi 44 -- -coronal section 1 56 ---[oculi] lacrimal 46,52 ---[oculi] orbit..! 46, 52, 120 ---[oculi] palpebral 46, 120 -- -sagittal section 169 -- arts 44, 45, 46 -- - mandibular Insertion 52

- --origin 52 ---sagittal section 168 -palatoglossus 105 - -innervation 89, 1 06 - palatopharyngeus 167 - pectoralis major - -spinal cord segments 357 - -sternocostal part, atrophy 346 - pharyngeal - -cranial nerve nuclei 68 - -innervation 86 - -upper, transverse section 165 - prevertebnl, Insertions 53 - procerus 44, 47, 120 - -sagittal section 168 - pte'Y!Iold 48, 58 --lateral 30, 50, 97, 99 ---section 159 - --- coronal 159 ---- saggltal 168 - ---transverse 1 63 - --function 48 - --Innervation 48, 77 - --Insertion 48, 52 - - -(lateral]lnferlor 35, 48, 50 - --(lateral] superior 35, 48, 50 - --origin 48 - - medial 24, 48, SO, 77, 95, 97 ---section - --- coronal 51, 158 ---- saggital 168 - - - - trilnsverse 1 65

- --function 48 - --Innervation 48, 77 - --Insertion 48, 52 - --origin 48, 52 - quadriceps femoris - --spinal cord segments 357 - --weakness 347 - receptor 179 -rectus - -capitis 53 - - - posterior 52 ----major 52,167 - --- sagittal section 167 - - lnfertor 73, 134, 136, 138 - --coronal section 156. 158 ---sagittal section 168 - --transverse section 162 - -innervation 72 - -lateralls 114,124,134, 138, 364 - --coronal section 157 ---sagittal section 168 - --transverse section 161 --medialis 114,124,134,138, 362,364 - --coronal section 156, 158 - --transverse section 161 - -superior 125, 134, 136. 138 - --coronal section 157 ---sagittal section 168 - --transverse section 160 - risorius 44, 46, 47 - rotators, external, we;~kness 350 - ulplngopharyngeus 1 45 - urtoltus 351 -semispinalis mpltls 52, 164, 167,168 - shoulder 68 -smooth 86 - sphincter pupillae 128, 362 - -Innervation 72, 128, 320 - spinalis cervlds 167

-splenius --capitis 52,165,167,168 - - cervlcls 169 -stapedius 146 - - blood supply 154 --contraction, triggered by sound 367 --Innervation 78, 147 --insertion 144 --paralysis 80 - sternodeldomastold 94, 96, gs, 169 --Innervation 88 --insertion 52 --paralysis 88 -styloglossus 53, 89, 1OS -stylohyoid 108, 112, 1 69 --Innervation 78, 95 - stylopharyngeus 169 -suprahyoid 48 -tarsalls --inferior 121 --superior 120 - temponlls 48, 97, 114 --accessory head 157 --coronal section 51, 157 --innervation 48. 77 --insertion 48, 52 --origin 48, 52 --sagittal section 169 --transverse section 160, 1 62 - temporoparletalls 45, 141 -tensor --fasciae latae, paralysis 351 --tympanl144,146,154 ---Innervation 74, 77,147 - -veli palatini 99. 145 --- innervation 74, 77, 86 -thenar, weakness 346 -tibialis anterior --spinal cord segments 357 --weakness 347 - tragla~s 141 - transversus --auriculae 141 --linguae 105 -trapezius 168 --innervation 88 --origin 52 --paralysis 88 --spinal cord segments 357 -tltceps -- brachll ---spinal cord segments 357 ---weakness 346 -- surae, weakness 347 -trunk. Innervation 282 -uvulae 103 --innervation 86 - vastus medialis, weakness 347 - vertimlls linguae 105 - zygomatlaJs 44, 46, 52 Muscular asynergy 245, 353, 355 Muscular rigidity 229 Mydriasis (pupillary dilation) 72, 128 Mydriatic agents 128 Myelencephalon see Medulla oblongata Myelin 176 -sheath 172, 176 Myelination 180 Myelosis, funicular 353 - lnfertor temporal 48

N

-mylohyoid 30, 108 -nuchal6, 11,26 -oblique 30 Myoepithelium 129 Myopia (near-sightedness) 125 Myotome 323

N Naris 18,164 Naris, posterior see Choana Nasal airway obstruction 111 Nasal passages 19 Nasal skeleton 18 Nasal spine 29 --anterior 4, 18,29 -- posterior 29 Nasal wall, lateral 18, 20 -nerves 116 -vessels 116 Nasolabial crease, deep 102 Nasolacrimal duct see Duct, nasolacrimal Nasopharyngeal fibroma, surgical approach 17 Nasopharynx 102 -coronal section 51, 159 -drainage from the para nasal sinuses 118 -sagittal section 166 -transverse section 164 NCNA transmitter (noncholinerglc, nonadrenerglc neurotransmitter) 324 Near sighted ness (myopia) 125 Nearvision 127 Neck -ofmalleus 146 -of stapes 1 46 Neocerebellum 239. 244 Neocortex 198, 202 -histological structure 200 -organization, functional 378 -phylogenetic ortgln 1 99 Neopallium 199 Neorubrum 229 Nerve block 335 Nerve conduction -velocity 117 -saltatory 176 Nerve ending, free 275, 327, 332 Nerve plexus 345 Nerve(s) -abducent (CN VI) 66, 67, 72, 73 --coronal section 159, 292 --emergence from bralnstem 227 -- innervation of ---extraocular muscles 134 ---orbit 137 -- Internuclear opthalmoplegla 365 -- passage through optic canal 138 -- passage through slrull base 72,90 -accessory (CN XI) 66, 67, 88, 226,227 -- passage through slrull base 88,90 --sections ---sagittal 168

401

N Nerve(s)

--- transverse 164, 237] --emergence from the bralnstem 227 --passage through the skull base 88,90 -afferent 272 -alveolar --Inferior 77,95,97,99,109 - - - sections ----coronal I 56,158 --- -sagittal 169 ----transverse 165 --superior 76 --- posterior branches 98. 1 01 -ampullary --anterior 83 --lateral 83,152 --posterior 83,149,152 -auricular --great 94, 142 --- distribution 95 --posterior 79, 95 - aurlculotemponl 74, 77, 92, 94, 96, 98, 99, 320 --auricular Innervation 142 --innervation --- ohuricle 142 --- of temporomandibular joint capsule 33 --In transverse section 164 - axillary 348 - buccal 77, 95, 98, 99, 103 --section ---coronal157 --- transverse 164 -caroticotympanic 85 -cervical --in sagittal section 167 --geniohyoid 109 -- menlngeallnnervadon 190 --posterior 52 --transverse 95 -ciliary 76, 137 --short 76, 137, 139, 320 -cochlear see Nerve, vestibulacochlear, cochlear part - cr•nlal 66-69. 172, 226, 227 -- CN I see Nerve, olfactory -- CN II see Nerve, optic -- CN Ill see Nerve, oculomotor -- CN IV see Nerve, trochlear -- CN Vsee Nerve, trigeminal -- CN VI see Nerve, abducent -- CN VII see Nerve, facial -- CN VIII see Nerve, vestibulocc>· chlear -- CN IX see Nerve, Glossapharyngeal -- CN Xsee Nerve. vagus -- CN XI see Nerve, accessory -- CN XII see Nerve, hypoglossal --emergence, sites 184, 227 --entry, sites 227 --ganglia 69 --in the cavernous sinus 138 --internal acoustic meatus 149 --nuclei 68, 228 see also Nucleus, of...nerve - cutaneous 348 --lateral femoral 350 --medial antebrachial 348 -ethmoidal 14, 76, 117 --meningeal branch 190

402

-facial (CN VII) 66, 67, 78, 79, 80, 81,226,227,242 -- branches 79, 92, 95, 96 -- - posterior auricular see Nerve, auri[ular

-- -stapedial see Nerve, stapedial --ganglia 69 -- In Infratemporal fossa 98 -- in tympanic cavity 144. 147. 154 -- innervation of ---auricle 142 -- -facial muscles 44 ---oralfloor 109 ---tongue 106 -- intra parotid plexus 94, 96, 113 --nuclei 68 -- passage through skull base 78,90 -- neflex -- -corneal 361 -- -stapedius 367 --section -- -coronal 292 ---sagittal 169 -- -transverse 235. 163 --taste sensi!ltion. b"ansmission

of 178,370 -femoral 350, 351 -frontal 76, 137 -- passage through orbit 14. 73. 137 -- passage through skull base 90 -genitofemoral 350 - glo111opharyngeal (CN IX) 66, 67' 84, 85, 226, 227. 242 --ganglia 69 -- innervation of ---auricle 142 ---meninges 190 ---oralfloor 109 ---tongue 105 --lesion 84 -- nuclei 68, 228 -- passage through skull base 90 --section -- -coronal 292 ---sagittal 168 ---transverse 164 --taste sensation 370 -gluteal 350 -- lesion 351 -hypoglossal (CNXII) 66, 67, 88, 89,226,227 -- innervation of ---oralfloor 109 ---tongue 105 -- lesion 105 --nuclei 68 --section ---sagittal 168 ---transverse 165,236 -lllohypogutrlc 350 -Ilioinguinal 350 -Infraorbital 76, 94, 120 -- branches 103 -- lnnervadon of muscles of mastlcadon 92, 96 -- passage through orbit 13, 17, 101,136 --section ---coronal114,158 ---transverse 163 -lnfratrochiNr 76, 96, 120, 137

- Intercostal 345 -lnerws]lntennedlus 78, 81, I 01' 242, 320 - -emergence from the brainstem 227 - - passage through auditory canal 149 - laatmal 14, 76, 320 - - passage through orbit 73. 137 - - passage through the skull base 90 - laryngeal 86, 87 - lateral pectoral 348 - lingual 74. 77. 80. 95. 97. 98. 320 - -innervation of - --oralfloor 109 ---tongue 106,370 --sections ---coronal 157 ---sagittal 167 - --transverse 165 - long thoracic 348 - mandlbular(CNV3 ) 74-77,80, 95, 98,99 - - branches 33. 48. 77. 96. 98. 99 - --sensory 92, 93, 94 - -innervation of - -- M. temporalls 97 - --meninges 190 - --muscles of mastication 48. 95 ---nasal septum 117 ---oral floor 109 - --orbit 137 - --temporomandibular joint capsule 33 ---tensortympani 147 - - pain fibers 334 - - passage through the skull base 90 --sections ---coronal157 - --transverse 163, 1 64 - masseteric 77, 99 - -Innervation - --of muscles of mastication 48 - --of temporomandibular joint capsule 33 --transverse section 164 - maxillary (CN V2) 74, 76, 80, 95, 99, 320 --branches 17, 76, 98,101,103, 117,190 - -ganglia 69, 320 - -Innervation of - --meninges 190 - --muscles of mastication 92, 96 ---orbit 13, 17,101,136, 137 --sections ---coronal 159 - --sagittal 168 - - pain fibers 334 - - passage through the skull base 90 -median 348 - mental 31, 77, 92, 94, 97 - musculocutaneous 348 - mylohyoid 95, 99, 1 09 - nasodllary 14, 76, 138 - - passage through the skull base 90 -nasopalatine I 03, 116, 320

--passage through the skull base 90 --branches 17,101,116,117 -obturator 350 - oa:lpltal 94-96, 142 --in sagittal section 168 - omlomotor (CN Ill) 66, 67, 72, 73,226,227 --branches 135 --ganglia 69. 320 --innervation of --- elttraocular muscles 134 ---orbit 14, 137, 138, 361, 365 --nuclei 68 --parasympathetic fibers 137. 316 --passage through orbit 14, 138 --passage through skull base 90 --sections ---coronal 159, 292, 300 ---sagittal 167.313 ---transverse 1 61, 234 -of omlar muscles 72 --course 73 -of pterygoid canal 17, 81, I 01, 320 - of tenwr muscle --tympani 77 --veil palatlnl 77,99 -olfactory (CN I) 66, 67, 70, 178 --coronal section 158 --nuclei 68 --passage through the skull base 90 -ophthalmic (CN V1) 74, 76, 80, 95,99 --branches 76, 190 --coronal section 159 --ganglia 320 --Innervation of ---nasal cavity 117 ---orbit 14, 71,137 --pain fibers 334 -optic (CN II) 66, 67, 71, 212, 358 --eyeball 1 24, 130, 178 --head. vascular supply 133 --ganglia 131 --lesions 208, 360, 363 --orbit 14, 71, 73,114,124,136 --passage through the skull base 90 --pupillary reflex 361 --section ---coronal 51,114,157,292 --- sagittal 167 ---transverse 161 --vascular supply, arterial 133 --vision 178, 358. 359 ---lossof129 -palatine 17,101,103,116,320 --passage through the skull base 90 -pelvic splanchnl~ 321 -petrosal --deep 10, 17,81,101 --greater 10, 17, 78,80,101, 145,149,154,320 --lesser 81 , 99, 144, 154, 320 --passage through the skull base 90 -pharyngeal 1 01 - phrenic 348 -pterygoid 48, 77, 99, 147

Neurosurgery

-pudendal 350 -radial 348 -Mcculu 152 - Mcculoampullary 149 -saphenous 351 -scapular, dorsal 343 -sciatic 350 -- pari! lysis 351 -spinal 172, 191,266, 267,290, 317,344,345 -- ganglia 180 -- lesion 349 -- rilmlsee Ramus (rami) --root -- -anterior see root Ventral

-- - posterior see root Dorsal -- sagittal section 167 -splanchnic 317,322 --greater 316 -- pelvtc 316, 321 -stapedial 78, 80, 147, 367 -subcostal 350 - supndavlcular 95 - supnortlltal 76, 93, 96, 120, 137 -- branches 14, 92, 138 -suprascapular 348 -supratrochlear 92, 94, 96 -temporal, deep 33, 48, 77, 97, 98 - thoncodorsal 348 -trigeminal (CN V) 66, 67, 74-79, 95, 21 3, 226, 227' 242 -- divisions 74, 75, 76, 77, 93-98,101 --- mandlbular(CNV1) 74-77, 80. 95. 98. 99 see also Nerve. mandibular ----motor branches 77 -- --sensory branches 77, 95 -- - maxillary (CN V2 ) 74, 80, 95, 98. 99. 320 see also Nerve. maxillary ----branches 76 ---ophthalmlc(CNVI) 74, 76, 80, 95, 99 see also Nerve, ophthalmic ----branches 14,76 --eye 138, 361 --fibers ---pain 334 ---somatic afferent 74 ---visceral efferent 74 --ganglia 69 --innervation of ---auricle 142 --- M. temporalls 97 ---meninges 190 --- muscles of mastication 44, 48, 92, 95, 96 --- nasalseptum 11 7 ---oralfloor 109 ---orbit 13, 14, 17,101,136, 137 ---temporomandibular joint capsule 33 ---tensortympanl 147 --lesions 75 --middle ear disease 145 --nuclei 68, 74 --sensory branches 95 --transverse section 162, 235 -trochlear (CN IV) 66, 67, 72, 73, 226,227

- -orbit 14, 134, 137, 138 - - passage through skull base 90 --sections - --coronal 159, 292 - --transverse 234 -tympanic 85, 144,320 -ulnar 348 - utrtcular 83, 152 - utrtculoampullary 149 - ogus (CN X) 66, 67, 86, 87, 226,227,316,320 - -accessory nerve see Nerve, accessory - - branches 85, 86 - -ganglia 69 - -

innerve~tion

---ofauride 142 - --of meninges 190 - --of tongue 1 06, 370 - - passage through base of skull 90 --sections

- --coronal 292 - --sagittal 168 - --transverse 164, 236 --taste 370 - vestlbulocochlear (CN VIII) 66, 67' 82, 83, 226, 227. 242, 367 --cochlear part 68, 82, 144, 149, 150,155,178,366 --Inner ear 143 - -ganglia 69. 82 - - passage through base of skull 90 --nuclei 68 --sections - --sagittal 169 - --transverse 163, 235 --vestibular part 68, 82, 144, 149, 155, 178, 368 - - vestlbulo-ochlear reflex 361 - zygornatl~ 76, 320 --orbit 14, 17, 101 Nervous system -animal 178 -autonomic see Nervous system, enteric

- central (CNS) - - afferents 1 78 - -axon myelinethin 1 96 - -development 182 - -direction, terms 185 - - efferents 178 - -flow of information 178 - -gray 172, 268, 270, 271, 272 --In situ 172 --Input 178 - -Interaction with per1pherill nervous system 1 81 - - matter location, terms 185 --myelination of axons 176 - -white 1 72, 174, 208, 266, 268 - entertc(vlsceral) 180,316,324 --autonomic 178, 180, 316, 318, 320, 324 --- cin:uit diagram 318 ---ganglia 316 - --Innervation of bowel 324 ---nerves 317 - --peripheral, central control 318 ---targetorgan 316,318,320, 325 - -development 182

--peripheral 172, 180 ---ganglia 180 ---Interaction with the CNS 181 --- myelination of axons 1 76 --somatic 178 -parasympathetic 316, 320 -- afferents 316, 322 --conduction ofvtsceral pain stimulus 322 --connections 320 --control center 221 --cranial nerve nuclei 68 --cranial part 316,320 -- efferents 31 6 --function 317 --interaction with sympathetic 325 --Intestinal innervation 324 --lumbosacral part 31 6, 321 --neurons --- postganglionic 31 8 --- preganglionic 31 7 --pain fibers 322 --target organ 316, 318,320, 325 - - transmitters 317 -peripheral (PNS) 234 -sympathetic 316 --activation 220 -- afferents 31 6, 322 --basic outflow 319 --blood pressure regulation 325 -- efferents 31 6 --Interaction with parasympathetlc 305 --neurons --- postganglionic 31 8 --- preganglionic 31 8 -- pain fibers 322 -- regulation of arterial calibers 325 --target organ 31 5. 31 8. 320, 325 --visceral pain 322 Neural crest 182 Neural folds 1 82 Neural pathway see Tract Neural tube 182, 256 Neurite see Axon Neurocranium 7

-bones 3 Neuroflbrlls, clumping of 174 Neurolllaments 1 74 Neuroglia 176 Neuroglial cells 1 76 Neurohypophysis see Gland, pituitary, posterior lobe Neuroma acoustic 82, 149, 239 Neuron branching pattern, In the reticular formation 231 Neuron(s) 173, 1 74, 175, 177, 216 -afferent see Neurons, sensory - •udltory pllthw•y 367 -basket 241 -bipolar 175, 368 -cerebellar 241 -cholinergic 318, 324 --digestive tube 324 -cortical types of 201 -division, life-long 70, 373 -efferent see Neurons, motor - glutamlnergic, central gray matter 335 -hippocampal 205

N

-hypothalamic 222 -Interneuron see Interneuron -lntramunl 317 -motor 89, 175, 181. 232,268, 270,273, 281,317,319,324, 328, 336, 338, 339, 342 --alpha 272, 273, 280, 281, 283, 328,336 --damage to ilxon 343 - - development 182 --effects of long tracts 273 --effects of Renshaw cells 273 --function testing 34.2 --groups 175 --inhibition, recurrent 271, 273 -- lesion 354 - - motor loop 341 -multipolar 69, 175 - neurosecntory 222 - noradrenerglc 318, 325,335 -- pain-inhibiting system 335 - ohplnal cord 270, 271, 272 -olfactory system 372 -paln 322 -- pain-Inhibiting system 335 -parasympathetic (visceromotor) 268,316,317 -postsynaptic 69,316,317,318 -presynaptic 69,316,317,318 -proJection 175, 271, 273 -- pain-Inhibiting 335 - - tracheotomy ---lateral spinothalamic 275 ---spinocerebellar 279 - psuedounlpolar 69, 175, 180, 317 -pyramidal 200. 201 -respiratory, expiratory 231 -retinal 131, 358 -- light reflex 363 -sensory (afferent) 175, 181, 319. 324,325 --activity 329 - - development 182 -- primary (first) 69, 180, 1 81, 274, 275, 276, 277' 278, 279, 325. 327' 358 --secondary (second) 274, 275. 277' 278, 279, 326, 327. 330, 333, 335, 358 --tertiary (third) 275, 277, 326, 327. 333, 358 - serotonlnerglc, pain-inhibiting system 335 -stellate 200, 201,241 -sympathetic 31 6, 317 --spinal cord 268 - rympllthoeX£1tatory 319 -synaptic ~J~~ttemsln 175 -taste 370 -types 241 -variants, function-adapted 1 75 - vestlbularsystem 368 -visual pllthWlly 358. 362 Neuron motor -alpha 89, 175, 232,273, 281, 328. 336, 340 -flrst354 -gamma 281. 328 -sensory input 342 Neuronal circuit of Papez, limbic system 374 Neurosecretion 222 Neurosurgery 335

403

N Neurothelium

Neurothellum 189, 191 Neurotransmitters 174 - Inhibitory 271, 273 - noncholinergic, nonadrenergic 324 - parasympathetic nervous system 317 - reticular formation 230 -sympathetic nervous system 317 -vesicle 175 Neurotubules 174 Niche, of round window 145 Ninhydrin test 350 Nissl substance 174 Nociceptors 328 Node/Nodus, of Ranvier 1 76 Nodule -of cerebellum 240 -of vermis 238, 315 Noradrenergic system, reticular fonnation 230 Norepinephrine 317,379 - blood pressure regulation 325 Nanna -facialis 4 - lateralis 2 -occipitalis 6 - vertlcalls 9 Nose 18,20, 114,116,118 - mimetic muscles 44, 46 -mucosal surface anatomy 114 - ostiomeatal unit 21 Nosebleed 59, 61, 1 00 -arterial ligation 119 Notch see Incisure Nuchal stiffness 190 Nuclear cataract 127 Nuclear reglon(s) -expiratory 231 -for vasomotor control 230 -for visual orientation in space 230 -motor 340 - pneumotaxic 230 Nucleolus 174 Nucleus (nudel) - acc:esory see Nudeus, visceral oculomotor (Edinger-Westphal) - accumbens, in sagittal brain section 313 -afferent (sensory) 68, 228 - emblguus 68, 84, 86, 88, 228 --in cross section of medulla oblongata 236 - anterfor 379 - basal 173, 198, 208, 215 -- forebrilln 375 -Cajal 368 -caudate 198,207,209,211, 21 5, 263, 340 --arterial supply 250 --head --of caudate nucleus 208. 329 --- efferent fibers from thalamus 218 --- relationship to lateral ventricle 292, 296, 306 --- reliltlonshlp to ventricular system 193 ---sections --- -coronal 292 ----sagittal 312 --- -transverse 305, 307

404

----sagittal 167 --sections -- -coronal brain 292, 294, 296 ---sagittal brain 167,312 -- -transverse brain 304, 307 -cenbellar -- lateral 240 -- medial 240, 342, 368 -cochlear 68, 82, 228, 366 - colllcular, superior 234 -cortically Independent 216 - cuneatus 217, 233, 277, 326, 331 -- accessory 237. 278, 326 -- connections with thalamus 218 -- in cross section of medulla oblongata 237 -cuneiform 333 - DarkschewltKh 368 - denbte 21 8, 235, 240 --section -- -coronal 300 -- - efferents 244 ---sagittal 313 ---transverse 163 - Delten 68, 82, 228, 342, 369 -divisions 217 -donal tegmental 225 -donal wgal 68, 86, 228, 230, 320,368 -- in cross section of medulla oblongata 236 - donolatenl 269 -Edinger-Westphal see Nucleus, visceral oculomotor -efferent (motor) 68, 228 - embollform 218, 240 -- coronal section 301 - - efferents 244 -facial 68, 78, 81, 228, 230 -- In cross section of pons 235 -- stapedius reflex 367 - fastlglal 240, 342, 368 -- coronal section 301 -- efferents 244 - glgantocellular 333, 338 -globose 240, 368 - - efferents 244

- mesencephalic, of trigeminal nerve 68, 74, 228 - -In cross section of midbrain 234 - -in cross section of pons 234 - motor 68, 228 --of trigeminal 68, 228,230 - --In cross section of pons 235 - nomencleture 216 - nonspecific 216 - oculomotor 364 - of ... nerve - -abducent 68, 72, 78, 228, 230, 364,368 - --in cross section of pons 235 - - - lesion 343 --accessory 237,271,368 - -trigeminal - --mesencephalic 68, 74, 228 - --motor 68, 228, 230, 235 - --principal pontine (sensory) 68, 72, 74, 228, 235 - --spinal 68, 74, 84, 86, 228, 331,334 ----cross section 235 - --- lesion 75, 330 ----parts 334 - --- somatotopic organization 334 - - hypogloSSill 68, 89, 228, 230 - --in cross section of medulla oblongata 236 - -oculomotor 68, 72, 228, 230, 362, 364, 368 - --In cross section of midbrain 234 - - - lesion 363 - --topography 72 --phrenic 271 - -trochlear 68, 228, 230, 364, 368 - - vestibulocochlear 236 - of amygdala 207 - -cortical 207, 293 - - lateral 207, 293 - of geniculate body 216, 219 - of hypothalamus, dorsomedi~l 220

--accessory 233 --In sagittal brain section 313 --Inferior 236 --superior 235, 366 -para brachial, medial 370 - paraventrlcular, of hypothalamus 215, 220,222 - parvocellulu 361 -Perlla 362 -pontine 342 -pontine, of trigeminal nerve 68, 74,228 - premotor 364 -preoptic 220 - preposltus 364 - pretectal 333 -principal, of trigeminal nerve 68,74,228 --In cross section of pons 235 -proper, of spinal cord 271 - pulposus 345 -Raphe 230 --mag nus 230, 333 -red 72, 213, 225, 229, 283, 337' 342 -- afferents 229 --connections from cerebellum 243 --sections --- coronal 296 --- (mid)sagittal 296,314 ---transverse 160, 234, 308 -Roller 82, 369 -saiiYlltory --Inferior 68, 84, 228, 320, 370 --superior 68, 78, 81, 228, 320, 370 -Schwalbe 82, 369 -sensory 68, 228 -septal 225 -somatic efferent (somatic sensory) 68. 228 -somatic efferent (somatic me>tor) 68, 228 -spatial arrangement 21 6 -specific 21 6 --connections with cortical are~s 217

- - in coronal section 301

- - mnnections with anterior

-- somatotopi[ organization 21 7

-- in cross section of pons 235 -gradlls 217,233,277,326,331 -- connections with thalamus 218 - habenular 372, 374 -hypothalamic -- connections -- -to anterior pituitary 223 -- -to posterior pituitary 222 --function 221 -- posterior 220 -Infundibular 220 -lntegntlon, thalamic 216, 21 9 --function 21 6 -Interpeduncular 225, 374 - lnterposltus -- anterior 218, 240 -- posterior 240, 368 -Interstitial 368 -lntralamlnar 21 6 -lateral 219 - lentiform 340 -lumbosacral 271 -mammillary 220 -medial 215, 219

pituitary 223 - of laterallemniKus 366 -of lens 340 - of posterior commissure 368 -of solitary tract 78, 81, 84, 86, 231,319 - - part(s) 68, 84, 86, 228 - --gustatory 370 - of spinel cord - -anterolateral 270 - - anteromedial 271 - -central 271 --Intermediolateral 271,319 - - lntermedlomedlal 271, 319 - - posterolateral 270 --posteromedial 271 - - retroposterolateral 270 -of the neuron 174 - oftrapemld body 366 - ofvestlbulocochleu nerve 68, 82, 228, 361' 368 - - efferents 368 - - topography 369 - olfactory, anterior 373 -olfvllry

-spinal --of accessory nerve 68, 88, 228 --of trigeminal nerve 68, 74, 84, 86, 228, 331' 334 - - - in cross section of medulla oblongata 236 --- In cross section of pons 235 --- lesion 75, 330 --- part(s) 334 --- somatotopic org~nization 334 -subcortical 198 - subthalamk 215, 224, 225, 340 --In sagittal brilln section 313 - suprachlasm.tlc 361 -supraoptic 220, 222 -tegmental 342, 372 -- pedunculopontlne 230 --posterior 374 -terminal, of optic tract 361 -thalamic 216,217,218 --anterior 216, 218, 221, 374 --- centromedlan 216, 21 8, 341 --dorsal 219 --Integration 21 6

Perception P

- -lntralamlnar 216 -- lateral geniculate (LGB) 216, 219 -- lilteral posterior 216 - -lilteral 216,219 -- medial dorsal 216 -- medial 21 9 -- medial genlculilte (MGB) 216, 219 --median 217 -- non-specific 216 -- reticular 215, 217 --sections -- -coronal 296, 298 ---sagittal 313 -- -transverse 305 --specific 216 --ventral anterior 216, 218 --ventral intermediate 216, 2111 --ventral lateral 216, 21 II --ventral posterolateral 216, 275,333 ---lesion 2111 --ventral posteromedial 216, 334 -- - gustiltory pathway 370 --ventrolateral 2111 --ventromedial 220 -- -connections with anterior pltultilry 223 -thoracic 279 -- posterior 271, 278 - tuberal 220 - tuberal of hypothalamus 321 - wntrol;rteral 217 - wstlbulu 65,112, 228, 361, 368.369 -- in cross section of pons 235 -- lateral 68, 82, 228, 342, 369 -- - efferents 244 -visceral afferent (visceral sensory) 68. 228 -visceral efferent (visceral motor) 68, 228 -visceral oculomotor (EdingerWestphal) 68, 72, 228, 320, 361362 -- pupillary reflex 361 Numbness 330 Nystilgmus 244 -optokinetic 361 -vestibular 148

0 OAE (otoacoustic emissions) 367 Occipital pole 199. 203. 200. 31 0 Ocdpitofrontillis 47 Ocdusion, carotid 264 Oculomotor function 361,369 -cerebellar function 244 -disturbance 244 Oculomotor palsy 72, 128, 135 -width of palpebral fissure 121 Olfactory cells 372 Olfactory centers 372 Olfactory disturbance due to head trauma 70 Olfactory pathway 372 Olfactory stimulus, reactions 372 Olfactory S)'5tem 21 6, 372 Ollgodendrocyte(s) 176

-function 177 Olive 86, 89, 227, 233, 239, 242 - blood supply 253 -fibers to Corti organ 367 - inferior 342 - superior 367 Operculum 198, 307 Ophthalomoplegla, Internuclear 365 Ophthillomoscopy 133 Opiates - effect on Intestinal motrlrty 324 -treatment with 335 Optic (physiological) cup 133 - embryonic 183 Optic chiasm 16, 71, 138, 192, 214, 219,220,313, 315,358 - arterial supply 250 - decreased blood flow 251 - In coronal brain section 303 - in transverse brain section 160, 308 -lesion 360 - primary 203 Optic fundus 133 Ora serrati! 124, 130 -attachment to vitreous body 125 Oral floor 108 Orbit 4,14,16,114 - adjacent cavities 1 6 - adjilcent structures 16 - arteries 137 -axis 125 -bones 14,16 - course of optic nerve 71 - innerviltion 137 - levels 136, 139 - neurovascular structures 136 - -openings 14 - panoramic tomogram 39 - posterior wall 138

-sections --coronal156 - -sagittal 168 --transverse 160, 162 -spread of disease 16 - subdivisions 1 36 -topography 138 -veins 64,137 Orbital floor 16, 136 Orbital region 120 Orbital roof 121,136 Orifice - of maxillary sinus 21 - pharyngeal, of eustachian tube 111,115,145 Oropharynx 102 - coronal section 51, 159 Ossicular chain, auditory 140, 144,146 - axis of movement 146 - blood supply 154 -function 146 -position in tympanic cavity 147 Ossification 3 Otitis media 145, 147 Otoacoustlc emissions 367 Oxycephilly 7 Oxytocin 222

p Pilchymeninx see Duril milter Pain 332 -affective component 335 -conduction, somatic, peripheral 332 -definition 332 -deep 332 - lower neck, acute 345 - neuropathic 332 - pathways 323, 333 --ending at subcortical levels 333 - perception 179, 216, 323, 335 --therapeutic intervention 335 - radicular 330 - referred 323 -relief 335 -site of origination 323 - som•tic 323, 332 -superficial 332 -thalamic 218 -visceral 322, 332 Palate -hard 28,102,115,158,165, 166 --coronal section 156 --neurovascular structures 103 --sagittal section 166 --transverse section 165 -softseealsoVelom 102,110, 115,166 --coronal section 158 --muscles 103, 145 --sagittal section 166 Paleocerebellum 239, 244 Paleocortex 198, 204, 207 Paleopallium 199 Paleorubrum 229 Paleothillamus see Nuclei, thalamic Pallidotegmentill bundles 225 Pallldum 229, 283, 329, 337 -connections with medial thalamic nuclei 219 - medial, connections with thal•mus 218 P•llium see Cerebrum Palsy, abducent nerve 135, 343 -due to middle ear disease 145 Pancreas 317 Panoramic tomogram 39 Papez circuit, in limbic S)'5tem 374 Papilla(e) 104, 371 -of optic nerve (blind spot) 124, 130,359 - - ..ttach ment to vitreous body 125 --structure 131 - lnterdentill 37 - lingual 104, 371 -vallate 104. 370 -wall 104 Papilledema 133 Paralysis - brachlofaclal 343 -bulbar 354 -central 208, 251, 343 - mmplete 343 -facial see sheet --acoustic neuroma 149 --central 47, 79

-- intranuclear 79, 80 --middle ear disease 145 --peripheral 79, 80, 121 -- suprilnuclear 47, 79 -Facies, mask-like 229 -flaccid 181, 343 -- brachial plexus lesion 349 --contralateral 343 -hypoglossal 105 --central 89 -- peripheral 89 -lower limb --contralateral 265 --spastic, Ipsilateral 343 -peripheral 349 -spastic 181, 263, 273,343, 355 -- lesion of spinal gray matter 353 -- progressive 354 -spinal, spastic, progressive 354 Paresis 287, 343 -increased intramedullary pressure 289 -ventral root lesion 346 Parestheslas 330 Parkinson disease 337, 340 Parotid tumor, extension 113 Parotidectomy, avoidance of facial nerve Injury 113 Pars, of anterior pltultilry 222 Path see Tract Pavlovian response 225 Peduncle -cerebellar 183, 227, 233, 238, 242,298 -- Inferior 227, 233, 2311, 242, 279. 298. 369 ---in cross section of medulla oblongatil 236 ---tracts 243 -- middle 227, 233, 238, 242, 298 ---blood supply 253 --- decuosation of 243 ---In coronal brain section 297, 298 ---In sagittal section 312 ---tracts 243 --superior 227, 233, 238, 242, 279,298 ---blood supply 253 ---In coronal brain section 297 ---In cross section of pons 234 ---in sagittal section 314 ---tracts 243 -cerebral 72, 183, 21 0, 212, 213, 226, 227, 229, 315, 376 -- blood supply 253 --compression of. against edge oftentorium 189 -- cou~e of pyramidal tract 338 -- In coronal brain section 296 --In sagittal brain section 312 --lesion of motor tracts 343 --of flocculus 238 --ofmamillarybody 221 -thalamic - - anterior 377 --dorsal 377 -- posterior 377 Perception 131, 366 -auditory 274 -extemal179 -sensory, unilateral loss of 330

405

P Perception

-visual, conscious 358 Perlarchicortex 204 Perikarya (cell bodies) 174, 180 - in gr;J)I matter 173 - in pain conduction 332 -of neurosecretory neurons 222, 232,233,272-278,281 Perilymph (Inner ear fluid) 146, 148 Perilymphatic space 148, 150 Perimetry 359 Perineurium 180 Periodontium 37 Periorbita 121,136,138 Periosteum, orbital 138 Phagocytic system, mononudear 176 Pharyngeal caudal, Innervation 86 Pharynx 102 -roof 110 Philippe-Gombault triangle 268, 277 Photoreceptors 131, 358 Pia mater 191 -ofthebraln 186,189,191 Pinealocytes 224 Piruitary gland see Gland, pituitary Piruitary stalk (infundibulum) 21 0, 212,215,222,315 Plagiocephaly (ilsymmetrlcal skull) 7 Plane/Piilnum -[plane] occipital 6 -[plane] canthomeatal 148 -[planum/plane] occlusal 37 - [planum] temporal 48, 381 Plate/Table -[lamina] tecti (quadrigeminal plate) 210, 212, 225,226, 229, 260,300,308, 315 --coronal section 299 -[plate] alar 182 -[plate] basal 182 -[plate] cribriform, of ethmoid bone 13,19,27,116, 139,190, 373 -- fracb.Jre 27 --injury 70 --transmitted structures 90 -[plate] perpendicular --of ethmoid bone 4, 16, 21, 27,114 --ofpalate 17,29,100 -[plate] ethmoid 13 -[plate] floor, of neural tube 182 -[plate] neural 182 -[plate] quadrigeminal (lamina tecti) 21 0, 212, 225, 226, 229, 260.300,308, 315 --coronal section 299 -[plate] roof 182 - [table] inner, of calvarium 9, 254 - [table] outer, of calvarium 9, 254 -age at ossification 7 -obstruction 123 - postlacrlmal sac stenosis 123 Plasmacytoma 9 Platysma 44, 46 - coronahection 156 -origin 52 Plegia 343 Plexus

- AueriNch 324

406

-basilar 187, 254 - brachial 348 -carotid 85, 137 --intern;ll 81,101,137,145 -- -sympathetic 90 -cervical 53,142 -choroid 192,196,210 --cells, function 177 -- embryonic 211 -- epithelial structure 195 --histological section 195 -- In sagittal section 169 -- In transverse section 160 -- of fourth ventricle 194, 240, 236,299 -- - blood supply 253 -- of lateral ventricle 194, 296, 300,308,311,312 -- of third ventricle 194, 258 --taeniae 195 -infl!rlor hypogastric 316 -lumbar, left. lesion 350 -lumboAcral 350 - Meissner 324 -myenteric 324 -neural 270 -parotid, of facial nerve 79, 94, 96,113 - pharyngNI 84, 86 -pterygoid 62, 64, 93, 256 -sacral, right. lesion 351 - Schabadasch 324 -submucous 324 -superior dental 76 -tympanic 84, 109, 144 -VI!nous -- of foramen ovale 90, 255 -- of hypoglossal nerve canal 65, 257 -- prostatic, Invasion by tumor cells 289 --vertebral 194, 289 -- - extl!rnal 9, 65, 256 -- --anterior 289 ---1nternal191,156,189 -- --anterior 289 -- --posterior 289 Pole -anterior, of lens 127 -frontal 199,310 -occipital 199, 203, 206, 31 0 -posterior, of lens 127 Pons 78, 184, 185,226, 338 -blood vessels 252, 253 -development 183 -foot 229 -lesion 343 -location 213, 292, 293, 308 -motor function 338 -nerves 66, 74, 78 see also Nerves, cranial -projection onto skull 187 -section -- coronal 295, 296 -- (mid)sagittal 312-315 --transverse 74, 161, 229,234, 235, 253, 295, 296, 343 Pontocerebellum 239, 244 -deficit symptoms 244 Pore, gustatory 371 Pores, nuclear 174 Position sense 218, 284 -loss 353, 355 -- unilateral 330

-tract 326 Position sense 284, 326, 328 Position sense, tracts for 276 Postsynaptic potenti;ll 174 Potential - membrane 174 - postsynaptic 174 - receptor 179 PPRF (paramedian pontine reticularfonmation) 364 Pre-BOt:zinger complex 231 Pressure 179, 218 - disturbance, occlusion of spinal artery 287 - in[reased - -intracranial, due to hemorrhage 262 - -Intramedullary 289 - Intracranial 82, 262 - Intramedullary 289 - intraocular 129 - receptors 84, 86, 319 -tracts 274, 276, 326 Presubiculum 375 Primordium of pituitary gland 183 PRL (prolactin) 223 Proceu -alveolar, of maxilla 114 - dlrary 126 -dlnold - -anterior 13, 25, 29 - - posterior 13, 25 - condylar, of mandible 30, 48 - - panoramic tomogram 39 - coronoid, of mandible 30, 48 -frontal, of maxilla 15, 18, 20 -jugular 26 -lenticular, of incus 146 -malleolar --anterior 146 --lateral 146 - mastoid 2, 6, 11, 22. 32. 148 -palatine, of maxilla 11, 16, 19, 29,114 - -sagittal section 167 - posterior cartilaginous, of nasal septum 19 - ptern~old 6, 24, 100 --plates 11, 17, 19, 25, 29, 48, so, 100,103 -pyramidal, of palatine bone 14, 17, 28, 147 - -Integration Into sphenoid bone 28 - spinous 191 -styloid 2, 6, 11, 22, 32, 106 - uncln~te, of ethmoid bone 20, 27 -zygomatic --of maxilla 11 --oftemporalbone 23,32,100 Prolactin 223 Prominence - mallear 143, 147 -of facial canal 144 - of lateral semicircular canal 144 Promontory, tympanic 144 Proprioception (deep sensation) 179,243 - balance regulation 368 -conscious - -Impaired 353 - - loss of 355 - -tract for 276, 284, 326

-cortex 329 -disturbances of 218, 287, 353 -tract for 326 -unconscious, tract for 278, 284, 326 Proprioceptors 326 Prosencephalon see Forebrain Protection acoustic 367 Protuberance -external occipital 6, 11, 26, 257 -mental 30 Ptosis 72, 135 -width of palpebral fissure 121 PTR (patellar tendon reflex), loss of 347 Puberty, precocious 224 Pulp of tooth 37 Pulvinar of thalamus 195,212, 216, 300, 308, 361 - afferents 219 - efferents 219 -in coronal brain section 298 -In sagittal brain section 167, 311,314 Puncta, lacrimal 122 Puncb.Jre -lumbar 197,267,291 -suboccipital 197 Pupll128 -constriction 128, 320, 362 -dilation (mydriasis) 72, 128 -reflex 361 -regulation of size 363 Purkin)e cells 175,241 Putamen 198, 207, 215, 224, 283, 329,340 -arterial supply 250 - efferents from thalamus 218 -hemorrhage 263 -In coronal brain section 159,294 -In sagittal brain section 31 0, 312 -in transverse brain section 305, 306 - motorsloop 341 -relationship to lateral ventricles 306 -relationship to ventricular system 193 -sagittal section 1 68 Pyramid -of medulla oblongata 227 -of vermis 238 Pyramidal cells 175,200, 281, 338 -definition 201 -in Ammon's horn 375 -large 201, 339 -small 201, 339 -visual cortex 203 Pyramidal motor system 336 Pyramid(s) 232, 342 -lesion of motor tract 343 - petrous 23

Q Quadrantanopla 360 Quadriceps see Muscles, quadriceps

Sensory disturbance S

R Radiation -of corpus callosum 377 -optic 71, 203,358,376 -- lesion, unilateral 360 --visual field 358 -thalamic 21 6, 21 7 Rage attacks, due to hypothalamic lesion 383 Ramus(Raml) -coronal section 158 -transverse section 165 -[rami] communicantes 191, 266,317 --gray317 --white 317,322 -[ramus]dorsal 95,191,317, 345,349 -[ramus] of mandible 30, 97 -[ramus]ventral191,317,34g Rebound phenomenon -positive 244 -testing 245 Receptive field 328 Receptor(s) 179 - a1/~1/P2 325 - cuteaneous 327 - muscarlnerglc 325 -muscle 277, 327 -pain 275, 328 --of organs 316 -primary 179 -potential 179 -secondary 1 79 -temperature 275 -tendon 179,277, 279,327 Recess -epitympanic 147 - hypotympanlc 147 -infundibular 192,210, 222 -lateral, of fourth ventricle 192 --in sagittalsection 313 -optic 308 -pineal 192, 224 -piriform 159 -preoptic 214 -sphenoethmoid 115 -superior, of tympanic membrane 147 -supraoptic 192, 21 0 Referred pain 323 Reflex 272, 361 -Achilles tendon 272 -- loss of 347 - addudor,loss of 347 -bleeps 272 - - loss of 346 -blink 46, 121 - - loss of 346 - bralnshm 361 -comul 74, 76,127,361 -diminished 352 - facial corneal 361 -facial stapedius 367 -fixed pupil 128 -gag 196 -Intrinsic 272 -light, pupillilry 361. 363 -- abolished 362 --limbs 363 -- -afferent 363 - - - efferent 363

- -on tympanic membrane 143 - monosynaptic 272 - ~liar tendon 272 --loss of 347 - polysynaptic 272 - pupillary 361 see also Reflex, light - quadriceps 272 --loss of 347 - salivary 370 see also Salivation -spinal 318 - stapedius 367 - -testing 147 -tibialis poshrlor 347 -triceps 272 - - loss of 346 - - surae, loss of 347 - Tr6mner 346 -vestibula-ocular 148,361 -visual system 362 Reflex arc 272 -visceral pain 322 - viscerocutaneous 323 Reflex hammer 272 Reflex testing 272, 342 Refraction of light 125 Renshawcells 271,281 - effects on alpha-motoneuron 273 Respiration, homeostasis 318 Respiratory center 231 Resting tremor 229 Reticular formation 225,236, 230, 280, 361, 368, 379 - circulatory center 231 - connections - -from the cerebellum 243 --from the hypothalamus 221 - -to the thalamus 218 - cross section of medulla oblongata 236 - mesencephalic 234, 364 - neuron branching pattern 231 - neurotransmitters 230 - nuclear region 230 - nuclei, group 230 -of bralnstem, ARAS 218 - pain pathway 333 - pontine 234 - - paramedian 364 - respiratory center 231 -spinal 269 - structural-functional relationships 230 Reticulum, rough endoplasmic 174,222 Retina 121,124, 130,212,358 - connections with pineal gland 224 -detachment 131,133 --ophthalmoscopic findings 133 - Inversion 358 - layers 124, 130 -limiting membrane 131 -nasal 358 - neuron, bipolar 175 - non-photosensitive part 130 - pars/part 130 --[pars] caeca 130 - - [part] ciliary 130 - - [part] iridial 130 - - [part] optical 1 26, 130 - - [part] photosensitive 130

-site of maximum visual acuity 131 -structure 131 -temporal 358 Retinal cone 131, 358 Retinopathy, diabetic 133 Retlnopretectal system 361 Retlnotectal system 361 Rhinencephalon 199 Rhinoscopy 119 Rhombencephalon (hindbrain) 192 -development 18 - midsagittal section 299 riFLM (rostral interstitial nucleus of the medial longitudinal fasciculus) 364 Rigidity, muscular 229 Rlng/Anulus - [anulus] flbrosus 345 - [ring] common tendinous 73, 134,138 - [ring] venous, spinal segmental 289 - [ring] Waldeyer 11 0 Ring-shaped drainage system, venous 259 Rods 131,358 Roofofpharynx 110 Roof plate, of neural tube 182 Root cells 271 Root sleeve 191, 2go Root, of tooth 36 Root -anterior, of spinal nerve, see Ventral root 227 -dorsal --compression 344 --clinical signs 347 -- dermatomes 344 --lesion 330, 345, 352 -cochlear, of vestibulocochlear nerve 236 -dental 36 - lateral, of optic tract 358 - medial, of optic tract 358 - nasociliary, of ciliary ganglion 76,137 - of tongue 104 - parasympathetic 321 --of clllary ganglion 137 --of otic ganglion 99 - posterior, of spinal nerve, see Dorsal root -sensory, of pterygopalatine ganglion 76 -sympathetic, of ciliary ganglion 137 -ventral 67, 182, 191. 227, 270, 290,317,322,344 --compression 344 --lesion 345, 346 --sprouting of efferent axons 182 --- clinicalsigns 347 --- indicator muscles 346 Rostrum of corpus callosum 205, 314,377 Rotational (angular) acceleration 140, 152, 368 Rotators see Muscles, rotator

s Sac -conjunctival 121, 124, 128, 130 -dural 291 -- relationship to spinal cord 269 - endolymphatlc 144, 148, 1 52 -lacrimal 120, 1 22 Saccades 364 Saccule 368 -vestibular 140,148,152 Saliva 112 Salivary reflex 370 Salivary stone 1 12 Salivation 225, 321, 370 -disturbance of 80 -In response to an olfactory stimulus 372 Salpingopharyngeal fold 110, 115 Salzmann, vitreous base of 125 Satellite cells, function 177 Scala -tympani 148, 150 -vestlbull148, 150 Scalp 9 Scaphocephaly 7 Schwann cell(s) -function 177 -nucleus 176 Sclera 121,124,128,130,136 Scleral spur 126, 129 Sclerosis -lateral amyotroplc 354 -multiple 177, 208, 365 sco (subcommlssural organ) 196 Scotoma 360 Secretion -bronchial 325 -Into digestive tube 324 Sectional anatomy 292-315 Seizure 330 Self-representation, loss of 219 Sella turcica 24, 222 Semlcanal of tensor tympani 145 Sensation -olfactory 372 -pain 218 --tracts for 274, 284, 326 -- unilateral loss of 330 -sexual, tract for 274, 276 -superficial 179, 329 --disturbance of 218 -temperature 179, 218 --lossof 352 ---unilateral of 330 --tracts for 274, 284, 326 -visceral, cranial nerves 66 Sensor 179 Sensorimotor function, cranial

nerves 66 Sensorimotor system,ln movement control 337 Sensory cell 179 -primary 179, 372 -secondary 179, 366, 368, 370 -vestibular, stimulus transduction 153 Sensory disturbance - brilchial plexus paralysis 349 -dissociated 330, 352 -- C4-T6 dorsal root 352 -dermatome 267 -facial 75

407

S Sensory disturbance

--ventral posterolateral nucleus ofthalamus 218 - pressure, lncreilsed,lntril· medullary 289 - radicular 330, 344 --sacral plexus 351 Sensory perception 178, 216 Sensory quillltles 178 Sensory system 328 -lesion 330 - receptive fields 328 - receptors 328 -stimulus processing 328 --modules, cortical 201. 328 Septum/Septa -arachnoid 189, 254 -dural 188 - In coronal brain section 293 --In midsagittal section 295 --In transverse brain section 305 --lesion 383 --topography 205 -lingual 105 -nasal 18, 21,115,156,158, 164,166 --arteries 61. 117 --bones 18 --bonypart 162 --cartilaginous 156, 163, 164 --coronal section 158 --nerves 117 --panoramic tomogram 39

--sagittal section 166 --transversesectlon 161,164 -of sphenoid sinus 29, 159 -orbital 1 20, 122, 136 -palatine 115 - pellucidum 199, 205,212, 215, 315 --arterial supply 250 Serotlnerglc system, reticular formation 230 Sexorgans,male 317 SFO (subrornical organ) 196 Sheath, carotid 62 Shock -decreased intestinal blood flow 324 - multisystem f•ilure in 324 -spinal 356 Shoulder, drooping 88 Signal convergence 131 Signal processing, cerebral, sex differences 379 Signal transduction 179 Sinus -carotid 84 -CIIVI!mous 10,21,60,64,93, 137. 187. 246, 254 --bacterial dissemination 93 --coronal section 159 --course of cranial nerves 138 --thrombosis 64 --transverse section 161 --tributaries 256 -confluence of see Confluence - dunl wnous 9, 254-257, 302 --confluence 9, 65, 186, 194, 255, 260, 302 --- in sagittalsection 166 --connections with external facial veins 93 --projection onto skull 187 --wall structure 154

408

-ethmoid 5,16,20,27,51,114, 118seealso Ethmoid cells -frontal 5, 8,13,16,19,114, 117,118 -- pneumatization 20

-- sagittal section 166 -Intercavernous 255 -marginal 254, 257 -mulllary 15, 16,20,28, 114, 118 -- coronal section 156, 158 -- endoscopy 119 -- panoramic tomogram 39 -- pneumatiZiltion 20 -- sagittal section 168 - - transverse section 163 - ocdpltal 187, 255, 258 - pannasal 5, 20 -- bony structure 21 -- drainage of secretions 118 --orifices 21 -- projection onto the skull 20 -petrosal 65, 93, 187, 254, 260 - - transverse section 163 --tributaries 256 - petro5quamous 255 -sagittal -- inferior 187, 188, 254, 258, 261,302 -- -tributaries 256 -- superior 51. 65, 1 86, 188, 194, 247. 254, 258, 302 -- - bridging veins, terminations of 186,188 -- -coronal section 157 -- -transverse section 160, 162 -- -tributaries 256 -sigmoid 9, 93,144,187,254, 260 -- accessory drainage 256 - - transverse section 164 -sphenoid 5. 10, 18,19,24,114, 116,118,145 --coronalsection 51,159 --flowofsecretlons 118 -- sagittal section 166, 168 - - transverse section 162 - sphenop;~~rletal 187. 254 - strlllght 188, 194, 254, 258, 260,302 --transverse section 160, 1 62 --tributaries 256 - trnsverse 9, 65, 187, 254, 258, 260,302 -- bridging veins, terminations of 188 -- sagittal section 168 --thrombosis 256 - - transverse section 163 --tributaries 256 -venous -- ofsclera 129, 132 --thrombosis 256 Sinusitis 5. 20, 118 -chronic 21 -ethmoid 20 Skin -Innervation 267 -nerve endings, free 275, 327, 332 -sympathetic effects 317 Skull (Cranium) 2-8, 22-24, 26, 52,70

- [skull] base 10, 11, 24, 26, 28, 53, 90, 164,247, 255 - - neurovilscular pilthwilys 90, 91 --bones 10 - -external 11 - --lines of fracture 5 --Internal 12, 13 ---llnesofforce 12 - blood vessels - -arteries 54-59 - -veins 9, 62-ii5, 257 - calvaria 8, 9, 186, 189, 262, 254 - - lntracrilnlal hemorrhage 262 -deformities 7 - muscle insertions

52

-[skull] neonatal 7 -sections --coronal 16, 27, 51,114, 156-159,189 - - (mld)saglttal 166-1 69, 190, 382 --transverse 16D-165 - sensory supply 95 -views - -anterior 4, 7, 20, 1 87 - - lateral 2, 3, 5, 7. 9, 20, 24, 48, 49, 52, 54, 55, 56, 75, 187 - - posterior 6, 7, 9, 65, 257 --superior 7, 8, 9 Sleep apnea 231 Soft palate (velum) see Palate, soft Solder lines 75, 334 Sole of root, anhidrosis 350 Somatotropic hormone (Somato· tropln) 223 Sommer sector 375 Sound conduction - apparatus 140 -from middle ear to Inner ear 151 Sound, preprocessing of active 367 Sound pressure. amplification in the ear 146 Sound waves, transmission through the ear 140,146 Space -Berger 125 - cortical representation 336 -danger 168 - endolymphatic 148, 1 SO - endoneural 194 - epidural 191, 290 - episcleral 136 -fontan• 129 - Garnier 125 - Hannover 125 - lateral pharyngeal space, course of internal carotid artery 246 - Nuel 150 -Petit 125 - pharyngeal 246 - retrobulbar 157 - subarachnoid 186, 189, 191, 262.290 - -optic nerve 131 --spinal 194 - subdural 191 Spatial orientation - acoustic-vestibular, nuclear region 230 - optic, nuclear region 230 Spatial sense 369 - cortical representation 336 Speech center 251

Speech -comprehension 381 -disorder 244 -production 380 Sphecoid bone see Sphenoid bone Sphincter, pupillary 72 Spinal cord 172, 173, 266-291, 316,317,326 -anesthesia 291 -autonomic pathways 283 -blood vessels 286-289 --arteries 286, 287 --veins 288, 289 -cauda equina see cauda equina -cerebrospinal fluid circulation 194,196 --obtaining samples 197 -cervical cord see Cord, cervical -columns 268,270, 271 --anterior see horn, anterior --lateral see horn, lateral --posterior see hom, posterior -covering 172, 191 -development 182, 266 -divisions 267 -dura mater 191 -enlargements 269, 270 -gray matter 173, 266, 268, 270-273 --Internal divisions 270 --intrinsic circuits 272, 273 --neurons 271, 272 --reflex arcs 272 -growth 267 -horns (columns) 182, 266, 268 --anterior (ventral) 182, 232, 266. 268-271, 280. 287, 354 --- blood supply 200, 287 --- nuclear columsn 270 ---reflex arc 272 --- somatotopic organiZiltlon 270,271 --lateral 182, 266, 268, 269, 316,319 --posterior (dorsal) 166, 169, 1 82, 266, 268, 271, 275, 278, 279,287,316 --- blood supply 287 --- reflex arc 272 -infarction 286 -Information flow 178, 221 -Intrinsic circuits 268, 272, 273, 277 -intrinsic f•scicles 268, 273 -lesion 289, 349,352-357 --level of 356, 357 --motor deficits 343, 354, 355 --sensory deficits 352, 353 -location 185. 191, 226,269.290 -lumbar cord see Cord, lumbar -lumbar puncture 197,291 -meninges 191 -motor pathways 337, 338, 342 -muscles 347 -nervous systems. inwlvement in

--autonomic 317,318 --parasympathetic 316, 321, 322 --sympathetic 31 6, 319, 322, 249 -neurons --gray matter 271, 272 -- lnterneurons 181, 271, 280, 281 , 283

Tightjunctions

--motor 89,181,182,271,273, 280, 281,283, 285,319,322, 323, 326, 368 --sensory 181, 271, 274-279, 319,322,323, 326, 332 --lesions 181 -organization 270, 271 --functional 266 -- somatotopic 270, 274, 276, 278 --topographical 266 -pain conduction 322, 323, 332, 333, 334, 335 -paralysis 289. 356 -passage through skull base 90 -reflex arcs 272 -sacral cord see Cord, sacral -section, transverse 90, 165, 173, 191. 255, 269, 275, 277. 279, 281, 283,287,289,319,331, 333, 334, 335, 338, 342 -segments 266, 267. 286, 287, 317,321 -sensory pathways 326, 327 -- lesions 330 -- pain 322, 323, 332, 333, 334, 335 - somatomotor integration 181 -suboccipital puncture 1 97 -thoracic cord see Cord, thoracic -tracts 232, 233, 234, 235, 237, 243, 273-285, 327. 330, 331, 333, 338, 342 -- ascending 233, 274-279, 284 -- descending 232, 280-283, 285 -- lesions 330 -vestibular system (balance) 368, 369 -white matter 173, 182,266, 268 Spinal nerve fibers 67 Spinal nerve see Nerve. spinal -dorsal root see Root, dorsal -ventral root see Root. ventral Spine 266, 267,269, 291 Splnocerebellum 239, 244 -deficit symptoms 244 Splenium of corpus callosum 205, 305,377 -in coronal brain section 300 -In sagittal brain section 314 -In transverse brain section 306 Split-brain patient 377, 380 Spot, yellow (maculalutea) 130 Spur, scleral 126, 129 Squama, occipital 26 Stance see also Ataxia Stance -motor as peds of 282, 285 -upright 368 Stapedius -baseof 146 - heild 146 -tendon 146 Stapes 143,144,146,148,367 -tilting movements 146 Statlns 223 Statollths 152 Status asth matlcus 325 Stl!llatl! cells 201 -cerebellar cortex 241 -cerebral cortl!x 200 Stl!ppage galt 351 Stereo hearing 366

Stereocilia 151, 366 - orientation 153 STH (somatotropic hormone) 223 Stimulus, loud acoustic 147 Stomach, Head zone 323 Stretch receptors of organs 316 Stria(e) - [fold] malleolar 143 - diagonal 372 - longitudinal 205 - mallearis 143, 147 -medullary --of fourth ventricle 227 --of thalamus 210, 225,372 - of Gennari 203, 358 -olfactory - - lateral 70, 21 5, 293, 372 - - medial 70, 372 - termlnalls 213, 221 - vascularls, of cochlear duct 150 Striate body see Body/Corpus striatum Stroki! 251, 263, 343 - hemorrhagic 264 - ischemic 264 Subclavian steal syndrome 247 Subcommissural organ 196 Subcortical centers, modulation of action 379 Subfornical organ 196 Subiculum 206, 375 Sublingual fold 106, 112 Suboccipital puncture 197 Substantia/Matter - [matter] gray 1 72, 198 - -cell groups 271 - -central 72, 299, 309 333, 335 - -cerebellum 240 --histology 173 - -Integrative function 272 - - neurons 271 - -of spinal cord 266, 268, 270 -[matter] white 172, 174,183, 198,208 - -cerebellum 240 - -fiber tracts 376 --histology 173 - -of spinal cord 266, 268 - -spinal cord 266, 268 -[substantia] gelatlnosa 269, 271,275 - -In cross section of medulla oblongata 237 -(substantia] nigra 72, 213, 215, 225, 283, 340, 342 - - afferents 229 - - blood supply 253 - - efferents 229 - -function 229 - -In coronal brain section 296 - -In cross section of midbrain 234 - -in midsagittal section 296 - -in sagittal brain section 313 - -in transverse brain section 160,308 - - location 229 - - motor loop 341 --parts 229 -[substance] perforate, antl!rior 70,225,372 Subthalamus 1 83, 211, 214, 224 -function 214

- location 224 Sulcus/Groove/Furrow - [groove] arterial 8, 13 -[groove] for sigmoid sinus 13, 23 -[groove] for superior sagittal sinus 8, 26 -[groove] for transverse sinus 13,26 -[groove] infraorbital 15 -[sulcus] anterolateral 227 -[sulcus] calcarine 202, 206,303, 315 --in coronal brain section 302 --in sagittal brain section 311 --in transverse brain section 309 -[sulcus] central 184, 199, 202, 329, 336, 378 -[sulcus] cerebral 184 - [sulcus] diencephalic 214 --ventral (hypothalamic sulcus) 21 0, 21 4, 220 -[sulcus] frontal, In coronal brain section 295 - [sulcus] hippocampal 206 -[sulcus] lateral cerebral 184, 199,202 --in coronal brain section 292 --middle cerebral artery 249 - [sulcus] median --[furrow] of tongue --posterior, of spinal cord 269 -[sulcus] palatine 167 -[sulcus] papillary 104 -[sulcus] parleto-occlpltal 202, 315 - [sulcus] postcentral 329 -[sulcus] posterolateral 227 -[sulcus] spiral, Internal 150 -[sulcus] telodlencephallc 183 - [sulcus] termlnalls of tongue 104,371 -[sulcus] terminalis 260 Surface ectoderm 182 Superior recess, of tympanic membrane 1 47 Supraopticrecess 195.210 Supraorbital margin 4 Suture 2, 6 -closure, premature 7 -coronal 2, 7, 8 -cranial 2, 6, 7 -frontal 7 - lambdoid 2, 6, 8, 257 -palatine --median 11,29,103 --transverse 29 - Silglttal 6, 7, 8, 257 --ossification 7 --premature closure 7 -sphenoid 7 -sphenoparietal 2 - sphenosquamous 17 -squamous 2 Sweat secretion, tract for 283 -disturbance 350 Sympathetic effects 317 -transmitters 317 Synilpse 173,174,175,216 - neuromuscular 73 Synaptic cleft 175 Syndesmosis 6 Syphllls,loss of pupillary light response 362

T

Syringomyelia 352 System, accessory optical 361 System, ascending reticular activation 218 System, central analgesic 335

T Table see Plate Tactile disk 328 Taenia -choroldea 195,212 -cinerea 227 - fornicis 195, 205 -thalami 195, 213 Tall see Cauda Tarsus 120 Taste 178, 370 Taste bud 104,370 -innervation 86 -microscopic structure 371 Tearfllm 123 Tectum of mesencephalon 72, 183, 226, 229 Tegmentum 183, 21 0, 224, 229, 337 Tela choroldea 211 Telencephalon see Cerebrum Temperature sensation see Sensation, temperature

Tentorium cerebelli 188, 190, 254, 302 -brain herniation 189 -transverse section 161 Territory, vertebrobasilar 246, 252 Testis, Head zone 323 Tetanus toxin 273 Thalamic radiation 217 Thalamus 71,193,210,212,214, 263. 275, 277. 326, 329 - afferents 219 -arterial supply 250 -connections --with bralnstl!m 216 --with cerebellum 243 --with cerebral cortl!x 216 -dorsal183,211,214,224,312 - efferents 219 -functional organization 21 6 -In coronal brain section 298 -In transverse brain section 306 -integration nuclei 216, 219 -motor 337 -motor loop 341 -pain Impulses 333 - reliltlonshlp to latl!rill ventricles 306 -relationship to ventricular system 193 -tract, ascending 216 -ventral see Subthalamus Thirst response. lack of 221 Thoracic cord see Cord, thoracic Thrombotic matl!rial, left atrium 264 Thrombosis 264 -lntracardlac 264 -sinus 120,145 -venous 265 Thyroid-stimulating hormone 223 Thyrotropin 223 Tight]unctlons 189, 191

409

T Tightjundions

-blood-brain barrier 197 - blood-CSF barrier 197 Tinnitus 149,252 Tissue b;uriers, cerebral 196 Tissue

- lymphatic, mucosa-ilssoclated 111 - lymphoeplthellal, of oral cavity 111 Tongue 102, 104 -base 115 -carcinoma of metastasis 107 -coronal section 156, 158 - innervation 1 06 -lymphatic drainage 107 - neurovascular structures 1 06 - sagittalsection 166, 168 -surface anatomy of mucosa 104 Tonotoplc principle 150 Tonsil -cerebellar 189,238 --coronal section 298, 300 --sagittal section 313 - lingual 104, 11 0, 115 -palatine 65,102,104,110,159, 168 --coronal section 159

--enlarged 110 --sagittal section 168 --structure 11 --veins 65 -pharyngeal 110, 115, 145 --enlarged 111 -tubal 110 Tooth/Teeth 4, 6, 10, 36, 37, 38, 40,41,42,43 -[teeth[ anterior 36 -coding --deciduous 43 --permanent 38 -[teeth[ deciduous (baby) 31, 42,43 -eruption 42, 43 - histology 37 -[teeth[ mandibular (lower) 33, 36,37, 77 -[teeth[ maxillary (upper) 36. 37.76 -parts 36 -[teeth[ permanent (adult) 31, 36,38, 40, 41,43 -[teeth[ posterior 36 -root 36 -supporting structures 37 -surfaces 38, 40,41 -[teeth[ wisdom 39,41 Torticollis 88 Torus tubarlus 102, 111, 115 Touch see Sensation. touch Trabecula, arachnoid 191 Trabecular meshwork, chamber angle 126 Tract(s) 2Ci6 -[path[ perforant 375 -autonomic 283 - a~cendlng 200, 217, 266,273, 274,276,278, 326 --course In cerebrum 329 --In cross section of spinal cord 274, 276, 278, 284 --synapse, intrathalamic 216 -central sympathetic 283 -central tegmental 229, 235, 242

410

-- In cross section of pons 235 -commissural, neocortical 205 - cortlconuclear 79 - cortlcopontlne 233 -- in cross section of midbrain 234 - cortlcorubral 229 -corticospinal 173, 232, 365 -- anterior 232, 273, 280, 282, 285, 338, 342 -- course through the internal capsule 298 -- degeneration, progressive 354 -- extrapyramidal fibers 342 --in sagittal brain section 313 -- lateral 232, 273, 280, 282, 285, 338, 342 -- lesion 354 - dentatorubral 229 - dentatothalamlc 218 -descending 266, 280, 282 -- extrapyramidal motor system 342 -- In cross section of spinal cord 280, 282, 285 -- lateral system 282, 285 -- medial system 282, 285 -extrapyramidal motor 282, 342 -- lesion 343 -- nuclei of origin 283. 342 -fiber 376 -fornix 205,221, 314 - frontopontlne, Internal capsule 377 - gastrolntestlnel 31 7 - habenulolnterpecluncul•r 225 - habenulotectal 225 - habenulotegmental 225 -hypothalamic-hypophyseal 221,222 -lemnlscal 233 -lumbosacral 350 - mammlllotegmental 221 - mammlllothalamlc 374 -motor, see also Tract, descending -- central. lesion 343 - ocdpltomesencephallc 342 -of posl:l!rlor funiculus 217, 276, 284, 327 -- axon, descending 277 -- central connections 277 -- lesion 330 -olfactory 70, 204, 372 - oiiWH:erebellar 233, 243 - ollwsplnal 273, 342 -optic 71,212,215,219,259, 358 -- in coronal brain section 293 --In sagittal brain section 313 -- In transverse brain section 160,308 -- lesion 360 --roots 358 - pallldorubral 229 - parependymal 283 - partetotemporopontlne 342 -posterolateral 269 -pyramidal 207, 231, 280, 282, 329, 336, 338, 342 -- anterior 237 -- arterial supply 287 -- blood supply 253

-

-course 281, 338 --In the Internal capsule 294 -disease 353 -explanation of terms 338 -in cross section of medulla oblongata 236 -In cross section of midbrain 234 -in cross section of pons 234 -in sagittal section 314 - lateral 237 - lesion 355 - - decreased blood flow to internal capsule 251, 263

- --intracranial herniation 1 89

--origin 200 - -topography 338 - retlculosplnal 273, 282, 285, 342,368 - -anterior 282 - retrollex 221 - rubrospinal 229, 273, 282, 285, 342 - -In cross section of medulla oblongata 236 - -in cross section of pons 234 - sen10ry, see Tract, ascending 216,326 -Military 235,236, 319 - spinal, of trigeminal nerve 235 - - lesion 330 - spinocerebellar (Gowers) 233, 243, 278, 284, 326 - -central connections 279 - -In cross section of medulla oblongata 236 - -in cross section of pons 235 - - lesion 355 - -somatotopic organization 278 - splnomesencephallc 333 - splnoretlcular 333 - spinotectal 234 - spinothalamic 274, 284, 327 --anterior 179,233,274, 284, 326,331 - --central connections 275 - --in cross section of spinal cord 274 - --lesion 330, 353 - --neuron, primary afferent 274 - -arterial supply 287 - - lateral 179, 218, 233, 274, 284, 326, 329, 331 - --arterial supply 287 - --central connections 275 - --In cross section of medulla oblongata 236 - --In cross section of midbrain 234 - --in cross section of pons 234 - --In cross section of spinal cord 274 - --lesion 330, 353 - -- neospinothalamic part 333 - --neuron, primary afferent 274 - -- paleospinothalamic part 33 - --somatotopic organization 274 - sympathetic, central 234, 236 - tectorubral 229 -tectospinal 273, 282, 285, 342 - -In cross section of medulla oblongata 236

--In cross section of midbrain 234 --In cross section of pons 234 -tegmentum, central 229, 235, 242 - temporopontlne 377 - thalamodngular 374 - trlgemlnothalamlc 218, 334 --dorsal 370 - tuberohypophyseal 221 - tuberolnfundlbular 223 - vestlbulocerebellar 243 -vestibulospinal 273, 285 --lateral 282, 342, 368 Tragus 141 Transentorhinal region, in Alzheimer disease 382 "Tree of life" 240 Trendelenburg sign, positive 351 Triceps see Muscles, triceps Trigeminal neuralgia 74 Trigeminal system 218 Trigone -collateral 192 -hypoglossal 89, 227 -of vagus nerve 227 - olfactory 372 Trigonocephaly (triangular skull) 7 Trochlea 120, 134, 139 Trochlear nente palsy 135 Truncothalamus (nonspecific thalamic nuclei) 216 Trunk muscles see Muscles, trunk Trunk -encephalic (bralnstem) 185, 187. 212, 226, 228, 230 -linguofacial 55 -of brachial plexus 348 -of corpus callosum 205, 292, 295, 296, 304, 314, 377 -pain pathway 333 -position, motor aspects of 282. 285 -sympathetic 316, 345 -thyrocervical 54 - thyrollngual 55 - thyrolinguofacial 55 Trypan blue dye. injection of 196 TSH (thyroid-stimulating hormane) 223 Tube, pharyngotympanlc (Eustachian) 22,145,147,154 -In sagittal section 167 -in transverse section 164

-innervation 85 -membranous lamina 145 - part(s) 145 -pharyngeal orifice 111,115,145 -safety tube 145 Tuber see Tuberosity Tubercle -anterior, of thalamus 213 -articular 23, 32 --panoramic tomogram 39 -mental 30 -of nucleus cuneatus 227 -of nucleus gracilis 227 - olfactory 372 -pharyngeal 11, 26 Tuberosity -masseteric 48 - pterygoid 48 - [tuber[ cinereum 196, 21 0, 214 -[tuberosity] maxillary 17,100

Visceromotor function V

u Umami (taste quality) 371 Umbo of tympanic membrane 143,147 Uncus 167, 206,293,312 Unit. ostlomeatal -of milxillary sinus-ethmoid ostium 118 -of nose 21 Utricle, vestibular 140, 148, 368 Uvea 124,128,130 Uvula 11 0, 115 -ofvermis 238.315 -palatal 1 02, 1 59, 166

v Vallecula of cerebellum 238 Vascular organ, of lamina termlnalls 196 Vasocorona 287 Vasoconstriction 325 -tract for 283 Vasodilation 325 Vasomotor function, control, nucleus 230 Vasopressin 222 Vater-Pacini corpuscles 277, 327 Velnls) -!venal cava 288 -alveolar, Inferior 156, 158, 169 - anastomotic -- inferior 256, 258 -- medullary 259 -- superior 256, 258 -angular 62, 64, 92, 94, 120, 137,256 -- anastomosis with superior ophthalmic veins 120 -- ligation site 93 - aKendlng lumbar 289 -azygos 288 -basal 256. 258. 260 -- region drained 259. 261 - basl..ertebral 289 - brachlocephallc, left 62, 288 -bridging 186, 188, 254 -buccal 157 - cenebellar 260 -- lateral 260 - cenebral 188, 255, 258, 265 -- deep 256, 258, 260 -- -anterior -- --cerebral 256, 258 -- --of septum pellucidum 258, 260 ---lingual 106 -- great 256, 258, 260 -- internill 256, 258 -- -in coronal brain section 298 -- - region drained 261 -- -thrombosis 265 -cervical, deep 256, 288 -choroidal 259 -- inferior 259 -- superior 260 -communicating 259 -cortical 258 -diploic 189,254, 256 -dorsal nasal 120, 137

- emissary 189, 254 - -condylar 9, 65, 90, 168, 256 - - mastoid 9, 65, 165, 256 - -occipital 9, 65, 256 - - parietal 8, 65, 256 - - passage through skull base 90 - -spread of lmectlon 9 - epidural 289 - episcleral 1 29 -ethmoidal 14 - fadal 62, 64, 92, 94, 98, 120, 137, 164,256 - -deep 64, 93 - frontal 256 - hemlazygos 288 -mac - -common 288 - -external 289 - Inferior of vermis 260 -lnfnlorbltal 14, 64, 137 - Intercostal 288 - Interpeduncular 259, 261 - Intervertebral 289 -Jugular - -anterior 62, 63 - -external 62, 94, 256 - -internal 22, 62, 64, 93, 107, 142, 145,254,288 - --passage through skull base 90 - --region drained 63 - --relationship to [ervical fascia 63 - --transverse section 164 - labyrinthine 90, 155 - lacrimal 64, 137 - lenticular 259 -lingual 106 - maxillary 62, 64, 93 -medullary 258 - - posteromedian 261 - -transverse 261 - meningeal 255 -middle - occipital 62, 65, 94, 257 - -Internal 258 - of bralnstem 261 - of caudate nudeus 259. 260 - of cochlear aqueduct 1 55 - of lateral wntrlcle 260 -of round window 155 - ofwstlbular aqueduct 155 - palatine, external 64 - retinal, central 132 -temporal, deep 64 Vestlbu..r aqueduct -auricular 62, 65 - of corpus callosum 260 -of head - -superficial 62 --deep 64 - -anastomoses 63 - ophthalmic 137 --inferior 14, 17, 62. 64.101. 132, 137. 256 --superior 14, 62, 64, 73, 93, 120,132,137,139,255,256 - --anastomosis with angulilr vein 120 - -- p01ssage through skull base 90 - pelnlsal 260 -pontine 261 - pontomesencephallc 261

-radicular 288 - retro~m~ndlbu..r 62, 64, 93, 256 -Rosenthal 259 -scalp 254 - semloval 259 -spinal 90, 289 -- ilnterlor 288 - - posterior 289 - subdavlan 62, 288 - subcostal 289 -submental 62, 1 06 - superflc..l --ascending cerebral 259 --cerebral 186, 256, 258 --descending cerebral 259 -superficial temporal 62, 92, 94, 98, 113, 160 -superior --cerebellar 260 --cerebral 186, 188. 254, 258 --dorsal cerebral 265 --medial cerebral 265 -- ofvenmls 260 - suprascapu..r 62 - supnrtruchlear 64, 137 -terminal 259 - thalamostrlate 212, 258, 261 --superior 260 -thyroid, superior 62 - tnonSVI!rse, of caudate nucleus 259 -vertebral 191, 256, 288, 290 -vorticose 64, 132 Velum -medullary --inferior 315 --superior 227, 238, 240, 279, 315 --- blood supply 253 -soft palate see Palate, soft Venous junction 62 - jugulofacial 1 07 Ventricle -fourth 187, 192, 226, 238, 240, 294,315 --in cross section of pons 235 -lateral 187. 192. 1 95. 208. 212. 215 --adjacent brain structures 193 --arterial supply 250 --central part 187,192,297 ---sections --- -coronal 295, 296, 299 --- -transverse 304 --embryonic 211 --enlarged 383 --horn ---frontal (anterior) 187, 192, 292,294, 312 ---occipital (posterior) 160, 187,192,205,296,299, 305,306 ---temporal (inferior) 187. 1 92. 205,207, 296, 299,375 --sections ---coronal 159, 292, 294, 300 ---Silglttal 312 ---transverse 1 60 --paired 192 --relationship to caudate nucleus 292,296 -third 187,192,195,210,215, 220,297,315

-- artertalsupply 250 -- In coronal brain section 294, 296 -- in midsagittal section 295 -- in tranwerse brain section

160,306 -- lateral wall193, 21 0 --optic recess 308 Ventricular system 192,292,302. 312 -enlarged 192 -location of basal nuclei 208 Vermis of cerebellum 238, 240, 260,279 - mrnnalsection 300, 302 -deficit symptoms 244 -in transverse brain section 1 60, 163,308 Vertebra 267 -cervical 166, 191, 267, 290 -lumbar 266, 267. 290, 291. 345 -sacral 267 -thoracic 267, 287,291 -venous plexus 289 -section --sagittal 166 --transverse 191, 289,290 Vertigo 80, 82, 244, 369 -of Indeterminate cause 148 - rotal)' 369 Vescicle -cerebral, derivatives 183 -diencephalic 211 -mesencephalic (midbrain) 21 1 -rhombencephalon 211 -telencephalic 211 Vesicles, glutamatergic 179 Vestibule, oral 1 02, 1 56, 167 Vestibular apparatuslvestlbular organ) 140,148,152 - afferentlmpulses 149 - stnJcture 152 -thermal function testing 148 -testing function separately for each side 148 Vestibular, dysfunction 80 Vestibular organ see Vestibular apparatus Vestibular schwannoma (acoustic neuroma) 82, 149, 239 Vestibular system 368 -receptors 368 Vestibule -nasal115 -of labyrinth 144,148 -oral102, 156,167 Vestibulocerebellum 239, 244 Vibration, tracts 276 Vibratory sensation 179, 218 -disturbance 287 -loss of 353 - tract for 326 - unllaterillloss of 330 Vicq-d'Azyr bundle (mamillothalamic tract) 21 5, 218, 221 Villi, arachnoid 186, 254 Viscera -abdominal, lnnerviltion 86, 320 -cranial nerve nucleus 68 -pelvic, innervation 321 -thoracic, innervation 86, 320 Vlscerocranlum see Facial skeleton Visceromotor function, cranial nerves 66

411

V Visions

VIsion 178 -distance 127 - m;udmum ilculty 124 Visual disturb;mce 208 Visual field 358, 359 - defects 360 -determination 359 VIsual pathwily 71, 212, 219, 227, 308,358 -geniculate part 358 --topography 359 - nongenlculate part 358, 361 - - light reflex 363 Visual system -accessory 361 -geniculate part 358, 360 - nongeniculate part 358, 361 - reflexes 362 - regulation of balance 368 VltamlnB1 -deficiency 220 VitaminB12 -deficiency 353 Vitrectomy 125 VOLT (vascular organ of lamina tenminalis) 196 Vomer 3, 4, 6, 10, 16, 24, 29, 103, 114 -coronal section 156 - nasal septum 18 -transverse section 1 62 Vomeronasal organ 373

w Waddling gait 351 Water balance, regulation of 221 White matter see Substantia/ Matter, white Window -oval 140,145,146,148,151 - round 148, 151 Wing/Ala -[ala] nasal 18 - [wing] greater, of sphenoid bone 2, 4, 13. 14, 16, 24,48,100 --in transverse section 162 - [wing] lesser, of sphenoid bone 4, 12, 19,25

y Yellow spot (macula lutea) 130

z Zona lncerta 224 Zone, danger, In the face 93 Zones, erogenous, afferents to hypothalamus 221 Zoster ophthalmicus 74 Zygomatic pillar 12 Zygomaticus 47

412