Human Body

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HUMAN BODY

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Human Body

Copyright © 2008 by Saddleback Educational Publishing All rights reserved. No part of this book may be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system without the written permission of the publisher. ISBN-10: 1-59905-234-2 ISBN-13: 978-1-59905-234-2 eBook: 978-1-60291-596-1



Human Body

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he human body is an organized collection of several body systems, which perform specialized functions. Some of these body systems, such as nervous, skeletal, and muscular are found throughout the body, while some systems, such as digestive, urinary, and endocrine are located in smaller areas. Weight of Brain The brain weighs less than 2.5% of our total body weight, but it burns oxygen and glucose at ten times the rate of other body organs. Length of Intestine The small intestine in human beings is 19.68 feet long.

• Healthy people can live with only one kidney. • There are three types of blood vessels: arteries, veins, and capillaries. • Blood vessels provide two important means of measuring vital health statistics: pulse and blood pressure. • The tooth is the only part of the human body that cannot repair itself. • For humans, the normal pulse is 70 heartbeats per minute. • It takes more muscles to frown than it does to smile. • The brain is more active and thinks more at night than during the day. • The human brain is 80% water. • Your fingernails grow almost four times as fast as your toenails. 

Cells, Tissues, and Organs

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he human body is made up of billions of cells. Cells are the basic structural and functional units of the human body. Tissues are an organization of several similar cells along with various intercellular substances between them. Organs are an organization of several different kinds of tissues arranged together to perform special functions.

Largest Organ Skin is the largest organ of the human body.

• Intercellular matrix is a non-living material, which fills the space between the cells. • Epithelial cells may be squamous, cuboidal, or columnar in shape and may be arranged in single or multiple layers. • Nerve cells or neurons are cells in nervous tissue that generate and conduct impulses. • There are about 210 different types of cells in the human body. • Human cells are made of several smaller organelles, such as nucleus, endoplasmic reticulum, golgi complex, lysosomes, and mitochondria. • There are four types of tissues in the human body: epithelium, connective, muscles, and nervous tissues. • Epithelium tissues cover organ surfaces and serve as protection and absorption.



Dissimilar Person Similar DNA Any two unrelated strangers anywhere on the planet share 99.9 percent of the same DNA.

Body Systems

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ody systems are the most complex components of the human body. They are an organization of several organs that perform complex functions for the body. The major body systems include circulatory, digestive, endocrine, immune, lymphatic, muscular, nervous, reproductive, respiratory, skeletal, and urinary.

• The muscular system allows the human body to move. • The circulatory system moves substances to and from the body cells. • The lymphatic system or immune system defends the body against diseases. • The skeletal system supports the human body and protects its internal organs. • The nervous system carries messages from the body to the brain and from the brain to the body. • The digestive system digests food and extracts energy and nutrients from it. • The respiratory system controls the gaseous exchange in the human body. • The endocrine system controls the secretion of hormones.

Combined Body Systems The functions of many body systems often overlap. For instance, the muscular and skeletal systems function together. As a result, both are sometimes combined and studied under the musculoskeletal system. 

Skeletal System

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he skeletal system provides support to the human body. It also protects delicate internal organs. The skeletal system is made of individual or joined bones. These bones are supported by ligaments, tendons, muscles, and cartilage. The skeleton continues to change its composition over a lifespan. On average, an adult human has 206 bones, but a baby is born with approximately 270 bones. Blood Forming Tissue The skeleton contains bone marrow, the blood forming tissue. Types of Skeleton There are two types of skeleton in the human body: the axial skeleton and the appendicular skeleton.

• The skeleton is the internal structure that holds the human body up and with the help of the muscular system, allows us to move. • Bones are the most important part of the skeletal system. • The longest bone of the skeletal system is the thighbone or femur. • The stirrup bone inside the ear is the smallest bone of the skeletal system. • Muscles hold the bones together and allow them to move.



Bone

B

ones are hard endoskeletal connective tissues. They support body structures and protect internal organs. There are two types of bone tissues: compact and spongy. They differ in density. Most bones contain both types of tissues.

Types of Bones There are four categories of bones: long, short, flat, and irregular bones. Bones are Active Bone cells rely on blood to keep them alive.

Producer and Store Bones manufacture blood cells and store for useful minerals.

• The bone that is broken most often is the collarbone. The scientific name for the collarbone is the clavicle. • The hyoid bone in the throat is the only bone in the body that is not attached to any other bone. • The human hand has 27 bones; your face has 14! • There are over 230 movable and semi-movable joints in the body. • Bones in men tend to be larger and heavier than in women. • The place where two bones meet is called a joint. Some joints move and others don’t.



Teeth and Jaw

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eeth are hard structures attached to the jaws. They are used for grinding and chewing food. The jaw is made up of two opposed bony structures that form the entrance of the mouth. The jaw consists of the upper and lower jaw. The upper jaw is known as the maxilla and the lower jaw is known as the mandible. The upper jaw is fixed while the lower jaw can move.

Permanent Teeth An adult has 32 permanent teeth that start to grow at about the age of 5–6 years.

Working Mechanism of Jaws The movement in the jaw is brought with the help of several muscles that are known as muscles of mastication.



• The lower part of the upper jaw holds the upper teeth. • Baby teeth start appearing at the age of 6 or 7 months. • The real name for baby teeth is milk teeth. • The hardest thing in the body is the enamel. • The first permanent teeth appear at about the age of six. • Human adults have 32 teeth called permanent teeth. • Human beings have three kinds of teeth: incisors, canines, and molars. • A tooth is fixed into the bony jaw socket and held in place by cement. • Digestion starts in mouth with teeth.

Ligaments and Tendons

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igaments are also found in many organs, such as the uterus, bladder, liver, and diaphragm. Ligaments are fibrous bands that are made of collagen. They keep the joints stable and allow flexibility and movement. Tendons are the fibrous connective tissues. They connect muscles to bones.

Ligament System in Spine There are two primary ligament systems in the spine: intrasegmental and intersegmental systems. Desmology “Desmology” is the study of ligaments.

• Bones are connected to each other by ligaments. • The muscles are attached to the bones with the help of tendons. • Ligaments and tendons may take a long time to heal after an injury because their blood supply is limited. • Tendons carry tensile forces from muscles to bones. • The word “ligament” comes from the Latin word ligamentum, meaning a band or tie. • If a ligament is made up of several thick bands of fibrous branches, it is called a “collateral ligament.” 

Hair and Nails

H

air is the thread-like growth in the epidermis of the skin. It provides body covering and is found only in mammals. Nails are protective coverings on the upper surface of the fingers and toes. They are formed from dead cells. These dead cells contain keratin, which is a fibrous protein.

Scalp Hair There are around 100,000 hairs in the human scalp.

• Nails grow at a rate of .019– .047 inches per day. • Hair grows more quickly in summer than winter, and more slowly at night than during the day. • There are no blood vessels in the epidermis, that is why a small scratch does not cause bleeding. • The larger part of the nail, the nail plate, looks pink because of the network of tiny blood vessels in the underlying dermis. • It is normal to lose 100 hairs per day from the scalp.

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Fastest Growing Tissue Hair is the fastest growing tissue in the human body after bone marrow.

Muscular System

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he muscular system is the network of muscles found in the human body. The system facilitates and allows movement of the body. The muscular system is also responsible for the functioning of important organs in the body such as heart and lungs. It also helps in keeping the body warm.

Busiest Muscle in the Body Eye muscles are the busiest muscle in the body. They may move more than 100,000 times a day.

Smallest Muscle Stapedius is the smallest muscle that measures 1/20 th of an inch.

• Muscles can only pull; they cannot push. • The largest muscle in the body is the gluteus maximus found in the buttocks. • There are 630 active muscles in your body and they act in groups. • Massete muscles are the strongest muscles of the body found on each side of jaw. • A smile uses 17 muscles while a frown uses 43.

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Muscles in Our Body

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here are more than 600 muscles in the human body. These muscles are found all over the body. Muscles that are attached to the skeletal system are divided into two groups: axial muscles and appendicular muscles. Axial muscles are muscles found from the head to waist. Appendicular muscles are muscles of the limbs.

Requirement of Muscles To work systematically, muscles need proper oxygen and food from blood.

Types of Muscles Human muscles are divided into three categories: skeletal, cardiac, and smooth muscles.

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• Muscles need oxygen and food for energy from blood in order to work properly. • Skeletal muscles make up 50% of body weight and there are 640 individually named skeleton muscles. • Skeletal muscle is made up of thousands of cylindrical muscle fibers often running all the way from origin to insertion. • Cardiac muscles are found in the heart. • A single muscle cell is called a muscle fiber. • Smooth muscles are of two types: multiunit smooth and single unit smooth. • Strains, sprains, cramps (charley horse), and repetitive stress injuries are the most common injuries of muscles.

Skin

S

kin is the outer covering of the human body. On average, the skin covers about 2 square yards of surface area. The primary job of the skin is to protect the body from external dangers. It also defends the body against infections and acts as a sensory organ detecting temperature, touch, and vibration.

Body Temperature Control By distributing heat through the skin and by preventing dehydration, skin helps to control body temperature.

Regeneration of Skin Skin is frequently regenerated and completely renews itself every 3–5 weeks.

• Weight of the skin: 7 pounds. • Skin is thickest on the palms and soles (.04–.18 inches) and thinnest on the lips and around the eyes. • Facial skin is approximately .004 inches thick and on the body is about .02 inches. • Length of the skin of an adult: 20 square feet of skin. • Humans shed about 600,000 particles of skin every hour—about 1.5 pounds a year. By 70 years of age, an average person will have lost 105.8 pounds of skin. • Each square half inch of the skin has 6 million cells, 5,000 sensory points, 100 sweat glands, 15 sebaceous glands, 10 hairs, and .03 inches of tiny blood vessels.

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Nervous System

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he nervous system is the information system of the body. It collects, stores, and analyzes all the information received by the body. The nervous system is the control system of the body. It is divided into two parts – the central nervous system and the peripheral nervous system. The entire nervous system is made of nervous tissues.

Nerve Impulses A nerve cell can transmit 1,000 nerve impulses each second.

• The human nervous system consists of around a hundred billion nerve cells or neurons. • The nervous system is made up of brain, brain stems, and nerves. • Most of the thinking takes place in the frontal lobe. • The entire surface of the central nervous system is covered with a fluid called cerebrospinal fluid (CSF). • In 1860 the average weight of a male brain was 2.99 pounds. Now a male brain weighs an average of 3 1/8 lbs. • The left side of human brain controls the right side of the body and the right side of the brain controls the left side of the body.

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Blood Transportation The carotid artery carries blood to the head and neck.

Brain

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he brain is a part of the central nervous system, located inside the head. It controls and coordinates bodily activities and the senses. The brain is divided into two halves or hemispheres. Both hemispheres communicate with each other through a bundle of nerve fibers known as corpus callosum. The brain is made of several parts, such as cerebrum, cerebellum, brain stem, hypothalamus, thalamus, limbic system, and midbrain. Measurement of Brain The average human brain is 6.57 inches long, 5.6 inches wide, and 3.72 inches high.

Technique to Record Brain Activity Electroencephalogram, or EEG, is a non-invasive technique used to record small changes of electrical activity in the brain, with surface electrodes on the scalp.

• An average adult male brain weighs about 3 pounds and a female brain is about 2.8 pounds. • A newborn baby’s brain grows almost 3 times during the course of its first year. • The biggest part of the brain is the cerebrum. It makes up 85% of the brain’s weight. • The brain receives about 100 million pieces of information at one moment that reaches the nervous system through receptors in the skin. • The adult human brain is about 2% of the total body weight. • One human brain generates more electrical impulses in a single day than all of the world’s telephones put together.

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Spinal Cord

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he spinal cord is a part of the central nervous system. It is a bundle of nerves that carries messages between the brain and the other parts of the body. The spinal cord is protected by a spinal column. The spinal column is made up of bones called vertebrae. The spinal cord is covered with three layers of protective membrane known as meninges. The space between the layers of meninges is filled with a fluid, which is called the cerebrospinal fluid. The cerebrospinal fluid is a clear and colorless liquid that protects the spinal cord.

Dimension of Spinal Cord The human spinal cord is about 16.92– 17.71 inches long and approximately as wide as a human finger. Structure of Spinal Cord The human spinal column is made up of 33 bones: 7 vertebrae in the cervical region, 12 in the thoracic region, 5 in the lumbar region, 5 in the sacral region, and 4 in the coccygeal region.

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• The base of the spinal cord has a cluster of nerves, which are the most sensitive. • There are 31 pairs of nerves in the the spinal cord. • The male spinal cord is longer than the female spinal cord. • The first bone or vertebrae of the cervical region of spinal cord is called the atlas. • The spinal cord develops before other parts of the body. • Receptors in the skin send the information to the spinal cord through the spinal nerves.

Neurons and Dendrites

N

eurons are the nerve cells. They are specialized cells that carry messages through the nerves. The German scientist Heinrich Wilhelm Gottfried von Waldeyer-Hartz coined the term neuron in 1891. Each neuron has several extensions known as the dendrites. These dendrites bring information to the neuron from other neurons.

Neurons in Brain There are about 100 billion neurons in the brain.

Controller for Neuron The nucleus is essentially the “brain” or control center for the neurons that hold all of the genetic information.

• Neurons vary in size from .004 mm to 100 microns or .1 mm in diameter. Their length varies from a fraction of an inch to several feet. • A typical neuron communicates with 1,000–10,000 other neurons, muscle cells, glands, etc. • Neurons cannot regrow after being damaged. • There are about 100 billion neurons in the brain. • Neurons can be divided into three major categories: sensory, motor, and interneuron. • Neurons grow at a rate of 250,000 neurons per minute during the development of the fetus.

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Central Nervous System

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he central nervous system is one of the major divisions of the nervous system. It consists of the brain and spinal cord. The central nervous system acts as the control system of the entire body. Some of the body functions controlled by the nervous system include muscle control, eyesight, breathing, and memory.

Division of Spinal Cord The spinal cord is divided into 31 segments. Composition of Brain The brain is made up of 77– 78 percent water, 10–12 percent lipids, 8 percent fat, 1 percent carbohydrate, 2 percent soluble organic substances, and 1 percent inorganic salts. 18

• There are two different types of regions in the central nervous system: grey matter and white matter. • The central nervous system does not include the peripheral nerves in the arms, legs, muscles, and organs. • The brain is made up of three main sections: the forebrain, the midbrain, and the hindbrain. • The brain contains about 100 billion nerve cells (neurons) and trillions of “support cells” called glial cells. • Cerebrospinal fluid flows uninterrupted throughout the central nervous system.

Lymphatic/Immune System

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he immune system works to fight against diseases and infections that affect the body. They produce antibodies that fight against antigens or disease causing bacteria, viruses, and pathogens. The lymphatic system is also associated with providing immunity to the body. It consists of the lymph vessels, lymph nodes, and lymphatic organs.

Autoimmune Diseases Sometimes the immune system fails to recognize body cells. It starts destroying them. This can lead to autoimmune diseases.

Lymph and Fat Lymph mixed with fat is called the chyle. Chyle is transported to the blood.

• Our immune system is an amazing network of cells that function from very basic to highly complex levels. • The immune system is divided into three parts: antigen-specific, systemic, and memory. • The antigen-specific immune system acts against a particular antigen. • The systemic immune system works throughout the body. • The memory immune system can fight against the same antigen even after a long period of time. • Multiple sclerosis, arthritis, and diabetes are autoimmune diseases. • The immune system of a young child has the capacity to respond to 10,000 different immune challenges.

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Lymph Nodes

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ymph nodes are bean-shaped organs that filter the lymph fluid. There are about five hundred lymph nodes in the body.

• Lymph nodes are surrounded by a fibrous capsule. • Lymph nodes range in size from a few millimeters to about .3–.7 inches in their normal state. • White blood cells are located within honeycomb structures of the lymph nodes. • Spleen and tonsils are large lymphoid glands. Their functions are similar to lymph nodes. • Lymph nodes also produce phagocytes that destroy bacteria and poisonous substances.

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Enlargement of Lymph Nodes When the body is infected, it increases the production of white blood cells. This leads to the enlargement of lymph nodes. Distribution The human body has about 500 to 600 lymph nodes. They are mostly found in the underarms, groin, neck, chest, and abdomen.

Antigens and Antibodies

A

ntigens are molecules, often found on foreign substances such as bacteria or viruses. They cause diseases in the body. The immune system fights against these invading particles by the production of antibodies. They tag, destroy, or neutralize antigens or disease causing molecules.

Bacteria

Virus

B-lymphocytes B-lymphocytes secrete antibodies to defend the body against parasites. T-lymphocytes T-lymphocytes protect the body against virus infection by killing the virus infected cells.

• Antibodies are protein molecules known as immunoglobulin. • Antibodies are y-shaped molecules. • Antibodies inactivate the antigen. • Antigens include bacteria, viruses, and mycoplasma as well as chemicals, food proteins, pollen grains, and dust particles. • Antibodies are produced by white blood cells to fight against antigens.

Antigens

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Circulatory System

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he circulatory system is made up of the heart, blood, and blood vessels. It transports nutrients, water, and oxygen to the body’s cells. It also carries away waste, such as carbon dioxide produced by the body’s cells. The circulatory system of an adult human has over 59,987 miles of blood vessels. The circulatory system is divided into three parts: pulmonary circulation, coronary circulation, and systemic circulation.

Blood is Colorless Hemoglobin, pigment present in the red blood cells, is responsible for the red color of the blood.

Quantity of Blood An average human has about 1.47 gallons of blood in the body.

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• Except the heart and lungs, all the other parts of the body receive their blood supply from the aorta. • The aorta is the largest artery of the body. • The pulmonary vein is the only vein in the human body that carries oxygenated blood, while all the other veins in the body carry de-oxygenated blood. • The red blood cells circle the whole body in 20 seconds. • The kidneys filter much of the waste from the blood.

Blood

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lood is a fluid that carries oxygen and nutrients to the body’s tissues and removes waste from them. Blood consists of plasma—a watery liquid— and three specialized cells. The specialized cells of the blood are: red blood cells, white blood cells, and platelets. Red blood cells carry oxygen throughout the body, white blood cells protect the body from diseases, and platelets help in the clotting of the blood.

Blood Groups Human blood is grouped into four types: A, B, AB, and O.

Identifier of Blood Type The Rh factor is a term for substances found on the surface of the red blood cells, and is named after the rhesus monkey, in which it was originally found.

• Blood is grouped into four types: A, B, AB, and O. • The average healthy adult contains between 5 and 6 quarts of blood. • A cubic millimeter of human blood contains about 5 million red blood cells. • Red blood cells are formed in the bone marrow. • Abnormal reduction in the number of red blood cells is known as anemia. • Medical terms related to blood often begin with hemo- or hemato- from the Greek word haima for “blood.” • Blood cells are produced in the bone marrow; the process is termed as hematopoiesis. 23

Blood Vessels

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lood vessels are tube-like canals that circulate blood to and from all parts of the body. There are four main types of blood vessels: arteries, veins, capillaries, and sinusoids. A blood vessel is divided into several parts, such as lumen, intima, media, and adventitia. Lumen is the hollow part of the vessel through which the blood flows. It is followed by a layer of tissues known as the intima. The intima is followed by another layer of tissues known as the media. The adventitia is the outermost layer of a blood vessel.

• Sinusoids are extremely small vessels located within the liver, spleen, and bone marrow. • The blood vessels provide two important means of measuring vital health statistics: pulse and blood pressure. • The largest artery of the body is the aorta. • Arteries and veins run parallel throughout the body, with a web-like network of capillaries connecting them.

Coronary Artery Coronary arteries are the blood vessels that carry blood to the heart muscle. 24

Construction of Arteries Arteries are tough on the outside and smooth on the inside so the blood can flow easily.

Heart

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he heart is a hollow, muscular organ. It is located to the left of the middle of the chest. The heart is of the size of a fist. It acts like a pump. It receives impure blood from the veins and pumps the pure blood into the arteries. It is made of cardiac muscles.

Heart Beats Per Minute The human heart beats 72 times per minute.

Blood Vessels of the Heart Arteries carry blood away from the heart and veins carry blood back to the heart.

• The human heart continues to beat even after it is taken out of the body. • A heartbeat is nothing but the sound produced by the closure of valves of the heart when the blood is pushed through its chamber. • The heart muscles will stop working only when we die. • A woman’s heartbeat is faster than that of a man. • The pumping of the heart is called the cardiac cycle. • During an average lifetime, the human heart will beat more than 2.5 billion times. • The aorta, the largest artery in the body, is almost the diameter of a garden hose. • The heart pumps more quickly during running and more slowly during sleeping.

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Ear

E

ars are the organs of hearing. They are also responsible for providing balance to the body. There are three parts of the ear: the outer ear, the middle ear, and the inner ear. These parts function together so that we can hear and process sounds.

Between Outer and Middle Ear The eardrum separates the outer ear from the middle ear. It is also known as the tympanic membrane.

Produces the Wax The ear canal is about 1 inch long and produces wax that keeps the canal clean and protects the ear from infection. 26

• The stirrup is the smallest bone in the human body. It is about .098 to 0.129 inches long. • Ears are made of cartilage. • Humans can hear sounds between 20–20,000 Hz. • Tinnitus is a symptom associated with many forms of hearing impairment and noise exposure. • The number of vibrations that are produced per second is called frequency. • The pinna, the outer part of the ear, serves to catch the sound waves. • Ossicles are the tiniest bones found in the middle ear. • Cochlea is the part of the inner ear filled with liquid. It contains hair cells that help in creating nerve signals for the brain.

Eye

E

yes are organs of vision. They are small in size—about .98 inches wide and .98 inches deep. Eyes are found in a hollow area of the skull called the eye socket. The front part of the eye is protected by the eyelid, which keeps the eyes moist and clean.

Non-transferable Eyes are connected to the brain by the optic nerve and cannot be reconnected once it has been severed.

Size of Eyes Eyes remain the same size throughout life.

• The eye is the only part of the human body that can function at 100% ability at any moment, day or night, without rest. • The human eyeball measures only about .98 inches. • The Ishihara test is a test used to detect your ability to see colors. • The human eye blinks an average of 4,200,000 times a year. • The retina is responsible for converting light signals into electrical impulses. • Eyelashes work with eyelids to keep dirt and other unwanted stuff out of your eyes. • The biggest part of the eye sits behind the lens and is called the vitreous body. 27

Smell and Taste

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dors enter the nose in the form of chemicals. They activate the hair cells located inside the nose. These hair cells are sense receptors that convert smell into electric signals and send them to the brain. The brain interprets theses signals as smell. When food enters the mouth, it passes through the tongue. The tongue has more than 10,000 taste buds. Taste buds contain taste receptor cells called microvilli. These cells react to different types of tastes found in the food and send nerve impulses to the brain. The brain interprets these impulses and identifies different tastes.

Smell is Not the Same No two people smell the same odor the same way. Odor

Example

Camphoric

Mothballs

Musky

Perfume/Aftershave

Floral

Roses

Peppermint

Mint Gum

Etheral

Dry Cleaning Fluid

Pungent

Vinegar

Putrid

Rotten Eggs

Loss of Sense of Smell Anosmia is the total loss of the sense of smell resulting from various causes. 28

• Children are likely to have much more subtle sense of smell than parents or grandparents. • Smells are detected in the nose by the specialized receptor cells of the olfactory epithelium. These are called olfactory receptor neurons. • The average human being is able to recognize approximately 10,000 different odors. • A diminished sense of taste is known as hypogeusia. • Flavor is what people commonly call the “taste” of food. • There are five basic tastes: salt, sour, sweet, bitter, and umami. • Humans have seven primary odors that help them determine objects.

Respiratory System

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he respiratory system is responsible for supplying oxygen to the blood. This is done through breathing. The body inhales oxygen and exhales carbon dioxide. The respiratory system is divided into two subgroups: the upper respiratory tract and lower respiratory tract. The upper respiratory tract includes body organs such as the nose, sinuses, and throat. The lower respiratory tract includes body organs such as the trachea and lungs.

• At rest, a person breathes about 14 to 16 times per minute. After exercise, it could increase to over 60 times per minute. • Newborn babies at rest breathe between 40 and 50 times per minute. By the age of five it decreases to around 25 times per minute. • Each lung contains 300–350 million respiratory units called alveoli, making it a total of 700 million in both the lungs. • Smoking makes it harder for our lungs to absorb oxygen. • The common cold is an infection of the lining of the nasal cavity and other parts of the respiratory system caused by viruses. • The level of oxygen in the blood is monitored by specialized nerve cells known as the peripheral chemoreceptors.

Water Loss We lose half a liter of water a day through breathing. Breathing Disorders Asthma is an increasingly common disease that causes coughing and makes it hard to breathe.

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Nose

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he nose is the organ of smell. The sense of smell is also known as olfaction. The nose helps in respiration. It lets the air enter into the lungs. In a day, about 21,140 quarts of air passes through the nose of an adult human.

Nose as a Filter The nose filters all the air that passes through it. Smell Fingerprint A smell fingerprint is the unique odor identity of every person.

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• A woman’s sense of smell is keener than a man’s. • The human body can recall smells with a 65% accuracy after the age of one year. • The cartilage gives shape and support to the outer part of the nose. • Rhinitis is an inflammation of the mucous membrane of the nose. • Memory is often associated with smell. • Rhinoplasty is a surgery through which the nose can be altered.

Lungs

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here are two lungs in the human body. Lungs are 9.84–11.81 inches in length and are separated by a structure called the mediastinum. The lungs are protected by the rib cage. The diaphragm is located at the end of the lungs. It helps the lungs inhale and exhale air. The lungs are protected by a covering of membrane, which is called the pulmonary pleura.

Weight of Lungs Male lungs weigh around 2.3 pounds, whereas female lungs weigh around 2.05 pounds.

• Male lungs average 2.3 lbs, while female lungs average 2.05 lbs. • The right lung is slightly larger than the left. • Women and children have faster breathing rates than men. • Yawning brings more oxygen to the lungs. • The total surface area of the alveoli (tiny air sacs in the lungs) is the size of a tennis court. • The lungs are protected by the ribs. • An estimated 90% of the lung is filled with air and only 10% is hard tissue. • Lungs are composed of smooth, shiny lobes.

Lungs Can Float in Water Lungs are the only organ in the human body that can float in water.

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Trachea, Bronchi, and Alveoli

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he trachea is a pipe that connects the mouth and nose to the lungs. It is also known as the windpipe. Bronchi are the divisions of the trachea that lead to each lung. Each bronchus (singular of bronchi) is further subdivided into several branches that terminate into tiny air sacs called alveoli.

Trachea

Structure of Alveoli Alveoli have radii of about 0.1 mm and wall thickness of about 0.2 mm. Structure of Trachea The trachea is flexible, stretching to between 4 and 5 inches long and about one inch in diameter.

Bronchi

Alveoli

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• The trachea is made of 16 to 20 rings of cartilage that are connected by ligaments. • The alveoli are found in the respiratory zone of the lungs. • Lungs contain about 300 million alveoli. • The trachea divides into two main bronchi—the left and the right. • The right main bronchus is wider, shorter, and more vertical than the left main bronchus. • Bronchitis is a viral or bacterial infection of the bronchi. • The bronchi tubes are responsible for cleaning the lungs.

Breathing Mechanism

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he breathing mechanism is related to the inhaling and exhaling of the air. The body uses oxygen from the inhaled air and gives off carbon dioxide through the exhaled air. Several body organs such as the nasal cavity, larynx, trachea, bronchus, alveoli, and lungs help in breathing. Normal breathing is controlled by the medulla oblongata of the brain.

• Inspiration is inhaling of air inside the body. • The diaphragm and intercostal muscles contract during inspiration. • The lungs expand during inspiration. • This expansion of the lungs lowers the pressure of the air inside the lungs compared to the air outside. As a result, air from outside flows into the lungs. • Expiration is exhaling of air from the body. • The diaphragm and intercostal muscles relax during expiration. • The lungs relax during expiration. • This relaxation of the lungs increases the pressure of the air inside the lungs compared to the air outside. As a result, air flows

Composition of Inhaled Air Inhaled air contains about 78 percent nitrogen, 20.8 percent oxygen, 0.04 percent carbon dioxide, and 1.2 percent water vapor. Composition of Exhaled Air Exhaled air contains 76 percent nitrogen, 15.3 percent oxygen, 4.2 percent carbon dioxide, and 6.1 percent water vapor.

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Urinary System

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he urinary system of the body consists of two kidneys, two ureters, one bladder, two sphincter muscles, and one urethra. The main job of the urinary system is to filter out the excess fluid and other substances from the blood. The urinary system reabsorbs some of the fluids and substances that it filters. The rest is excreted from the body in the form of urine. Some other body parts such as lungs, skin, and intestine also excrete waste. Male urinary system Female urinary system

Sphincters Sphincters are the circular muscles in urinary bladder that prevent the urine from leaking. Urine Discharge Organ The urethra is a special urinary organ that finally discharges urine from the body.

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• All the blood in our body passes 300 times through each kidney everyday. • Nephrons are the structural unit of kidneys. • Nephrons send about six cups of urine to the bladder per day. • The urinary bladder can hold around 2 cups of urine for about 2 to 5 hours. • In males, the urethra is about 7.87 inches in length. • In female, the urethra is shorter, about 1.18–1.57 inches in length. • Over 60 percent of an adult’s weight is water.

Kidney

K

idneys are organs of the urinary system. They are bean-shaped organs located on the backside of the abdomen. They are found on each side of the spine. A normal kidney is about 3.93 inches long and 1.96 inches thick. The kidneys weigh around 10.5 oz, which is about 0.5 percent of the total body weight. They receive huge amounts of blood —around 20 percent of the blood pumped by the heart—to carry out their normal functions. As Endocrine Gland Kidneys also function as endocrine glands and secrete an enzyme known as renin. One Kidney Can Function Well If the body loses one kidney, the other kidney enlarges and does the work of two.

• Each kidney contains one to two million nephrons. • Some of the most common kidney diseases and conditions are polycystic kidney disease, nephrosis, lupus nephritis, diabetic nephropathy, rhabdomyolysis, kidney stones, and renal tubular acidosis. • Diabetes is the most common cause of kidney failure. • The kidneys excrete a variety of waste products produced by metabolism, including the nitrogenous wastes: urea and uric acid.

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Digestive System

T

he digestive system consists of organs that break down and absorb food. The system includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. The process of digestion begins in the mouth and ends as the solid waste that gets stored in the rectum. There are some other organs, which help in digestion, but are not part of the digestive tract. They are the tongue, salivary glands, pancreas, liver, and gallbladder. Digestion Period It takes the body six hours to digest a high-fat meal versus two hours for a carbohydrate meal. Glands in Stomach The human stomach contains about 35 million small digestive glands.

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• For the average person it takes eight seconds for food to travel down the esophagus, 3–5 hours in the small intestine, and 3–4 days in the large intestine. • The stomach produces a new lining every three days in order to avoid digesting itself in the acid that it produces. • When you eat, the body digests the food so that cells can use it to make energy. • Acids and enzymes eat away at the surface of food to break it down. • The human stomach contains about 35 million small digestive glands. • The large intestine takes undigested food paste and turns it into solid waste by removing the water.

Esophagus and Stomach

T

he esophagus is a muscular tube that connects the mouth to the stomach. The stomach is a hollow, muscular organ. It lies between the esophagus and the first part of the small intestine. The food passes from the mouth to the stomach through the esophagus.

Extension of Esophagus The esophagus is about 9.8 inches long and it extends through the neck and chest into the abdomen. Diseases of Stomach Common disorders of the stomach include: stomach ulcer, gastritis, and stomach cancer.

• The connection between the stomach and the esophagus is called the cardiac sphincter. • The human stomach can be distended up to four liters, which is more than one gallon. • As food is liquefied in the stomach, it is slowly released into the small intestine for further processing. • Food in the stomach that is partly digested and mixed with stomach acids is called chyme. • The interior of the stomach is able to secrete about 2.1–3.1 quarts of gastric fluid everyday.

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Small and Large Intestine

T

here are two sections of the intestines: small and large intestines. The intestines extend from the stomach to the anus. They absorb the digested food.

Length of Small Intestine The small intestine with a 19.6 feet length, is the longest section of digestive tube. Absorption Process The large intestine is responsible for the absorption of water and excretion of solid waste material. Food products are absorbed by the small intestine.

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• The large intestine is about 4.9 feet long, which is about one-fifth of the whole length of the intestinal canal. • The most obvious difference between the small intestine and the large intestine is that the large intestine is wider. • The cecum is a sac with a closed end. It is the very first part of the large intestine. • The lining of the small intestine secretes a hormone called secretin, which stimulates the pancreas to produce digestive enzymes. • Disorders of intestine include Crohn’s disease, constipation, Irritable Bowel Syndrome, or infections caused by worms. • Food products are absorbed in the small intestine whereas the large intestine is responsible for the absorption of water and excretion of solid waste material. • The large intestine hosts several kinds of bacteria that deal with molecules the human body is not able to breakdown itself.

Liver

T

he liver is the largest internal organ of the body. It lies on the right of the stomach and plays a major role in metabolism. The liver is mostly made up of hepatic cells. These are specialized cells that perform chemical processes.

Filtration Power The liver filters over a quart of blood each minute.

Capacity to Regenerate The liver is the only organ which has the capacity to regenerate even after being removed almost completely.

• Insulin controls the amount of sugar in the blood by moving it into the cells, where it can be used by the body for energy. • The liver is the largest and heaviest internal organ of the body and weighs about 3.5 pounds. • The liver affects nearly every physiological process of the body and performs over 500 different chemical functions. • Hepatitis is the inflammation of the liver. • The liver is mostly made up of hepatic cells. • Liver cells take several years to replace themselves. • A healthy liver processes 190 gallons of blood per day. • The liver detoxifies poisonous

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Pancreas and Gall Bladder

T

he pancreas is an organ of the digestive and endocrine systems. It is pistol-shaped and located behind the stomach and above the intestines. The gall bladder is an organ of the digestive system. It is a pear-shaped muscular sac located near the duodenum.

• The gall bladder stores and concentrates bile produced in the liver. • The pancreas produces two hormones: insulin and glucagon. • The pancreas releases enzymes that help in digestion of food. • Cholecystectomy is a surgery to remove the gall bladder. • Length of human pancreas is 5.9–9.8 inches. • Pancreatitis is a condition that affects the pancreas.

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Gall Stones Gall stones are one of the major and common causes of gall bladder diseases.

Herophilus (335–280 BCE) Herophilus, a Greek anatomist and surgeon, discovered the pancreas.

Absorption and Excretion

N

utrients from the digested food are mostly absorbed by the small intestine. Undigested materials are converted into feces and excreted out of the body. The small intestine also absorbs water and electrolytes, while the colon absorbs leftover nutrients and water from the undigested food.

• The liver acts as a filter for the blood. It cleans out toxic waste and acid in the blood. • Water vapor and carbon dioxide is driven out by the lungs. • The small intestine is covered with tiny finger like projections known as villi. • Digested food is absorbed by the body through four processes: active transport, passive diffusion, facilitated diffusion, and endocytosis. • Nutrients enter the blood through the microvilli.

Role of Skin Skin performs an important role in excretion by removing excess water, salts, and waste such as urea.

Waste Material The human body has CO2, nitrogen compounds, and salts as most important waste products. 41

Male Reproductive System

R

eproduction is essential to keep a species alive. It is the biological process by which one organism creates another. Reproduction in humans requires two kinds of sex cells or gametes. The male gamete is the sperm and the female gamete is the egg or the ovum. The male reproductive organs are located both inside and outside the pelvis. The organs include: testicles, epididymis, and vas deferens, the seminal vesicles, prostate gland, and penis.

Accessory Glands Seminal vesicles and the prostate glands are known as accessory glands that provide fluids which lubricate the duct system and nourish the sperm. Hormone for Sperm Production FSH (Follicle Stimulating Hormone) is responsible for stimulating and maintaining sperm production.

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• About 500 million sperm mature everyday in a normal male adult. • The average life span of a sperm is about 36 hours. • The male organs produce and transfer sperm to the female for fertilization. • Testicles produce and store millions of sperm cells. • Testosterone is the hormone that causes males to develop deeper voices, bigger muscles, and body and facial hair, and it stimulates the production of sperm.

Female Reproductive System

T

he female reproductive system is a group of organs that are necessary for reproduction. It includes ovaries, fallopian tubes, uterus, and vagina. The female reproductive system enables a woman to give birth to a child. It produces eggs, and protects and nourishes the fertilized egg until it is fully developed.

Largest Cell The largest cell in the female human body is the ovum or egg present in the ovaries.

Capability of Giving Birth The female human body is capable of giving birth to 35 children in one lifetime.

• In the womb, the baby’s body is covered by a thin layer of hair, but as soon as the baby is born, it disappears. • In preparation for fertilization, the egg will be moved through the fallopian tube in order to meet the man’s sperm. • Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. • The female has a reproductive system located entirely in the pelvis. • The vagina is about 3.14– 4.7 inches long in a matured woman.

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Pregnancy and Birth

H

umans undergo sexual reproduction. The male and female reproductive cells unite and form a single cell, which ultimately forms the baby. The female goes through a gestation period of about 40 weeks. During this period, the zygote develops within the womb into a full-grown baby.

Premature and Post Mature Babies born before the 37-week mark are premature, and those born after the 43-week mark are considered post-mature babies. Fetus The baby is refered to as a fetus while in the developmental stage inside the mother's womb. 44

• The baby lives inside a transparent membrane called the amniotic sac. • The arms begin to form at about 3 weeks. • Fingernails are present at 7 months. • The eyelids remain closed until the 7th month to protect the eyes. • An ultrasound in the beginning of pregnancy can find out the age of pregnancy correctly.

Genetics

G

enetics is the study of genes and heredity. It tells us about the transfer of traits from parents to their offspring. Genetics is the scientific study of how particular traits and characteristics are transmitted from one generation to the other. In the 1850s Gregor Mendel was the first to conduct experiments on heredity. He is regarded as the father of genetics.

Bateson Bateson first used the term “genetics” publicly in 1906 in an international conference on genetics (London, England).

• In 1903 chromosomes were discovered to be hereditary units. • The science, which grew out of the union of biochemistry and genetics, is widely known as molecular biology. • Genetic diseases are caused by a defect in the person’s genes. • Genetic engineering deals with the modification of the genetic structure of a living being. • Genes are made up of deoxyribonucleic acid or DNA. • Genes carry traits, diseases, and all other hereditary information.

Genetic Diseases Some of the common genetic diseases are sickle cell anemia, down syndrome, cystic fibrosis, hemophilia, muscular dystrophy, and color blindness. 45

DNA

D

NA or deoxyribonucleic acid is the basis of life. Although most of the DNAs are found in the nucleus of the cell, some of them are also found in the mitochondria. DNA has a doublehelix structure, and it is made of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These chemical bases are known as nucleotides. Each DNA contains millions of these chemical bases attached in a particular way: ‘A’ combines with ‘T’, and ‘C’ joins with ‘G’.

Flexibility of DNA DNA is a flexible molecule that can bend, twist, and kink. • DNA encodes all genetic information. • DNA is found directly in the cytoplasm. • “Base pair” is a name given to two nucleotides paired together. • “Junk DNA” represents sequences that do not appear to contain genes or to have a function. • The largest human gene is on the X chromosome—the dystrophin gene.

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DNA Discovery American biochemist James D. Watson and British biophysicist Francis Crick published the first description of the structure of DNA in 1953.

DNA Testing

D

NA testing is also known as DNA fingerprinting. It is mostly used in criminal investigations. DNA testing is believed to be more reliable, as DNA cannot be altered. DNA testing is even more reliable because apart from identical twins, no two individuals can have same set of DNA.

Mode Methods of DNA testing are RFLP analysis, AmpFlp analysis, STR analysis, Y-chromosomes analysis, and mitochondrial analysis.

• The most popular ancestry tests are Y-chromosome (Y-DNA) testing and mitochondrial DNA (mtDNA) testing. • Mitochondrial DNA is a DNA in the human passed down to the child by the mother without any change. • A person’s maternal ancestry can be traced using his or her mitochondrial DNA. • DNA testing is often used in situations involving child custody and/or support, adoption, inheritance, and immigration. • DNA paternity and maternity testing is the most accurate method of confirming biological relationships between alleged parents and children. • The DNA in each of our cells not only dictates the color of our eyes, but also contains the footprints of our ancestors.

Invention Sir Alec Jeffreys at the University of Leicester announced the invention of DNA testing in 1985.

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Enzymes

E

nzymes are molecules that help to speed up various chemical reactions taking place inside the cell. Enzymes have a unique shape and they are made of amino acids. Their unique shape helps them to carry out specific chemical reactions. Restriction enzymes are enzymes that recognize and cut DNA at a specific target.

• En-zyme means “in yeast”, so called because that is where these proteins were first found. • Every function of the body is dependent upon enzymes, including breathing, seeing, hearing, and thinking. • Enzymes are proteins, and the shape of proteins determines their function. • Enzymes are known to catalyze about 4,000 biochemical reactions. • Enzymes work very fast as they carry out their task thousands of times per second. • Humans have two large categories of enzymes: digestive enzymes and systemic enzymes. • The level of enzymes in the human body decrease with age.

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Wilhelm Kühne Wilhelm Kühne (1837–1900), a German physiologist coined the term enzyme in 1878. Categories of Enzymes Enzymes in the human body are categorized into digestive enzymes and systemic enzymes.

Hormones

H

ormones are chemicals secreted by the endocrine glands. They control growth, differentiation, and metabolism in the body. Hormones are of two types: amino acid hormones and steroid hormones. The secretion of hormones is regulated by the chemicals in the body, other hormones, and the nervous system.

Steriod hormone

Hypothalamus The hypothalamus secretes chemicals that stimulate or suppress hormone secretions from the pituitary gland. Sex Hormones Testosterone, secreted by testes, is the male sex hormone. Estrogen and progesterone are female sex hormones secreted by ovaries.

Ovaries

• Prolactin hormone secreted by the pituitary gland activates milk production in women. • Thyrotropin hormone secreted by the pituitary gland stimulates the thyroid gland to produce thyroid hormones. • Thyroxine hormone secreted by the thyroid gland controls the rate at which cells burn fuels from food to produce energy. • Insulin secreted by the pancreas helps to maintain a steady level of glucose or sugar in the blood. • Catecholamines hormone secreted by the adrenal glands increases blood pressure and heart rate when the body experiences stress. • Melatonin hormone secreted by the pineal gland regulates the wake-sleep cycle. 49

Genome

G

enome refers to the complete genetic instructions for an organism. They are also like a library of instructions. A gene is a sequence of adenine, thymine, guanine, and cytosine. These nucleotides combine together to provide the instructions. The normal human genome consists of 3 billion base pairs of DNA in each set of 23 chromosomes from one parent.

Genome Size Genome size refers to the total amount of DNA contained within one copy of a genome. Genome Degradation Genome degradation is the process by which a genome shrinks relative to its ancestor. 50

• In 1920 Hans Winkler, Professor of Botany at the University of Hamburg coined the term “genome.” • In 1976 Walter Fiers was the first to establish the complete nucleotide sequence of a viral RNA. • Phage-X174 was the DNA-genome project to be completed by Fred Sanger in 1977. • In 1995 the first bacterial genome of Haemophilus influenzae was completed. • The Human Genome Project was organized to map and to sequence the human genome. • Currently, there are two human genome projects: the first is being produced by a group of international government bodies and organizations, and the second by a private company—Celera Genomics. • Shotgun sequencing is the technique used in breaking the DNA into millions of pieces.

RNA

R

NA or ribonucleic acid is similar to DNA except that it has a single strand. RNA is made of four chemical bases, similar to DNA, except for thymine. Uracil takes the place of thymine in RNA. The process of protein synthesis is carried out with the help of RNA.

• RNA is found in animal and plant cells. • Messenger RNA is RNA that carries information from DNA. • RNA is usually a single-stranded molecule and has a much shorter chain of nucleotides. • Synthesis of RNA is usually catalyzed by an enzyme. • RNA also serves as the hereditary material in some of the viruses. • The discovery of ribozymes added to the evidence that RNA, not DNA, was the earliest genetic material. • In 1981 American biochemist, Thomas Cech, discovered that certain RNA molecules act as enzymes.

Ribonuclease-P The enzyme, ribonucleaseP, is in all organisms. It is the part of RNA that has enzymatic activity.

T-RNA

In Laboratory Synthesis RNA was produced in a laboratory for the first time in 1955. 51

Cloning

C

loning refers to the creation of an identical copy of an original organism. A clone is genetically identical to the original organism. Cloning started in 1970s, when scientists experimented with frogs and toads. The possibilities of cloning a human became a reality when a sheep named Dolly was cloned.

Technologies of Cloning DNA cloning, reproductive cloning, and therapeutic cloning are different technologies of cloning.

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• Therapeutic cloning, also called “embryo cloning,” is the production of human embryos for use in research. • Cloning is asexual reproduction. • Cloning of any DNA sequence involves the following four steps: amplification, ligation, transfection, and screening/selection. • The first mammal to be cloned was a sheep called Dolly. She was born on July 5, 1996, at the Roslin Institute, Edinburgh, Scotland. • Biomedical scientists use stem cells to generate all the other specialized types of cells in the human body. Bone marrow is a rich source of stem cells.

Endocrine System

T

he endocrine system is a system of ductless glands in the human body. These glands are called endocrine glands. The endocrine glands produce and secrete hormones into the blood or lymph systems. The endocrine glands are pituitary, thyroid, parathyroid, adrenal, Islets of Langerhans in the pancreas, and the gonads (testes and ovaries). Hormones in the Human Body The human body contains 30 amazing hormones, which regulate activities like sleep, body temperature, hunger, and managing stress in times of crisis and so on.

Puberty Puberty for girls usually begins between ages 9 to 13, and for boys the age is 10 to 15.

• The pituitary gland is known as master gland because it makes hormones to control several other endocrine glands. • Diabetes mellitus is a disease in which glucose is not sufficiently metabolized. It results from deficiency of insulin. • Acromegaly is a disease in which the growth hormone is produced throughout a person’s lifetime. • The pituitary gland regulates the growth of bone and tissue. • The thyroid gland regulates the rate of growth and metabolism. • The gonads are the main source of sex hormones. • The pancreas produces two important hormones—insulin and glucagon.

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Blood Transfusion

A

blood transfusion is the transferring of blood or blood-based products. Blood transfusions take place from one person into the circulatory system of another. It happens in many situations, such as massive blood loss and severe anemia. In 1818 Dr. James Blundell performed the first successful blood transfusion to treat hemorrhage. Universal Blood Donors Persons belonging to the O blood group are called universal blood donors.

First Effort for Blood Transfusion 15th century chronicle, Stefano Infessura, described the first historical attempt at a blood transfusion.

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• Every three seconds someone needs blood. Blood and blood products are used to treat accident and burn victims, cancer patients, and other patients undergoing surgeries and medical treatments. • One unit of blood is roughly the equivalent of one pint. On average, an adult has approximately seven to nine units of blood. • Each year approximately 8 million volunteer donors give about 14 million blood donations. • About 12 million units of red blood cells and whole blood, 8 million platelet units, and 3 million plasma units are transfused annually. • More than 90 percent of transfusion complications have been attributed to the presence of leukocytes in allogeneic blood.

Kidney Dialysis

K

idney dialysis is used to remove impurities from the blood. Blood is pumped out of the body and cleaned inside a machine called a dialyser, which acts as an artificial kidney. Dialysis is of two types: hemodialysis and peritoneal dialysis. Most patients with damaged kidneys receive hemodialysis.

• Dialysis works on the principle of the diffusion of solutes across a semipermeable membrane. • In 1913 John J. Abel “dialyzed” animals by directing their blood outside the body and through tubes with semipermeable membranes. • In 1924 German doctor Georg Haas performed the first dialysis treatment involving humans. • Willem Kolff is acknowledged as the father of the modern kidney dialysis. • In 1943 Willem Kolff invented a crude kidney dialyzer. • The next generation of Kolff’s dialyzer was a stainless steel KolffBrigham kidney, which paved the way for the first kidney transplant in 1954. • In 1962 Dr. Belding Scribner started the world’s first outpatient dialysis facility.

Father of Dialysis Scottish chemist, Thomas Graham, was known as the “Father of Dialysis.”

Parallel Plate Dialyzer The Parallel Plate Dialyzer was a kidney dialyzer that worked by directing the flow of dialysis solution and blood through alternating layers of membranous 55

Yellow Fever

Y

ellow fever is a viral disease. Aedes aegypti mosquitoes transmit the yellow fever virus. This disease mainly affects the liver. Symptoms of yellow fever include jaundice, muscle pain, high fever, bleeding, and sometimes death.

Tropical Fever Yellow fever is a tropical disease caused by infected mosquitoes, and found only in Africa and South America.

Vaccination for Life A single dose of yellow fever vaccine provides protection for 10 years and probably for an entire life. 56

• Yellow fever is preventable by immunization. • There are two kinds of yellow fever: jungle and urban yellow fever. • The “yellow” in the name is explained by the jaundice that affects some patients, causing yellow eyes and yellow skin. • Yellow fever results in epidemics that can affect 20% of the population. • Yellow fever is caused by the yellow fever virus, which belongs to the flavivirus group. • Fever, headache, and muscle ache may occur 5 to 14 days after vaccination. In rare instances, encephalitis (inflammation of the brain) has developed in very young infants.

Mumps

M

umps is a viral infection that is highly contagious. Mumps primarily affects children under nine years of age. This disease causes the swelling of the parotid gland. Symptoms of mumps include high fever, headache, loss of appetite, and bumps on the cheek.

Transmission of Mumps Mumps is a viral disease spread through direct contact with saliva, secretions from the respiratory tract, and urine of an infected person.

Prevention of Mumps The mumps vaccine is known as MMR, which is given in one injection with the measles and rubella vaccines.

• Mumps is caused by the myxo virus. • Mumps infections are uncommon in children younger than 1-year-old. • Mumps can lead to inflammation and swelling of the brain and other organs, though this is not common. • About 1/3 of people have no symptoms. • The virus may cause a miscarriage if a woman becomes infected during the first three months of pregnancy.

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Gout

G

out is a form of arthritis that occurs mostly in men. It is caused by excess uric acid crystal deposits in the blood and joints. It is an extremely painful disease, which usually affects the big toe. Symptoms of gout include red, swollen joints, and acute pain.

Obesity Increases the Risk Excessive weight can increase the risk of developing hyperuricemia and gout due to availability of tissues for breakdown that leads to excess uric acid production. Attack of Gout Gout usually affects a single joint and may begin anytime but often at night.

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• The leading risk factor for gout is a buildup of uric acid in the bloodstream—a condition known as hyperuricemia. • About 90% of people with gout have reported at least one flareup in their big toe. But they can also experience symptoms in other joints, including the hands, elbows, and knees. • Men are at least four times more likely to develop gout than women. • Men who develop gout usually do so between the ages of 30 and 50. Women are more likely to develop gout after the age of 60. • Events such as strokes, heart attacks, or surgery may also cause

Chickenpox

C

hickenpox is an infectious, viral disease caused by the varicella virus. It is an acute, communicable disease that usually occurs in young children. A person suffering from chickenpox is covered with red spots all over the body. Symptoms of chickenpox include fever, headache, tummy ache, loss of appetite, and classic pox rash on the skin.

• Chickenpox is spread by direct contact or breathing in from nose and throat secretions. • Incubation period lasts 10–21 days before symptoms appear. • A chickenpox (varicella) vaccine, approved in 1995, is recommended for all children ages 1–13 who haven’t already had chickenpox. • Chickenpox has a superficial resemblance to smallpox. It is completely different and less severe. • The number of pox is different for everyone. Some people get just a few bumps; others are covered from head to toe. • Chickenpox is infectious from about 2 days before the rash appears, and lasts until all the blisters are crusted over.

Viral Disease Chickenpox is a contagious viral disease spread from person to person directly from broken chickenpox blisters. Chickenpox Complications Although chickenpox is a mild disease, it can cause problems for pregnant women, newborn babies, and people having certain immune system problems.

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Allergy

A

n allergy is an abnormal response of the body's immune system. It occurs because of the body’s high sensitivity to certain substances such as oil, fungi, molds, pollen, animals, plants, etc. Symptoms of allergies include runny nose, watery and itchy eyes, sneezing, asthma, and allergic shiners (dark circles under the eyes) in children.

Antibody Immunoglobulin E Allergic people make a special antibody called immunoglobulin E that react with environmental substances in a harmful way.

Symptoms of Allergies Sneezing, runny nose, itchy throat, red or swollen eyes.

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• Anaphylactic shock is a severe allergy which affects many organs at the same time causing a rapid decrease in blood pressure, fainting, and, occasionally, death. • People with allergies have an antibody called IgE (immunoglobulin E). • Feathers, wool, dyes, cosmetics, and perfumes may act as allergens. • The most common allergens are animal dander, pollen, house dust, house dust mites, molds, some drugs, and many foodstuffs, especially fish, eggs, milk, and nuts. • Conjunctivitis is an allergic condition of the eyes mostly in adults. • Asthma may begin at any age and one can suffer from attacks that obstruct the flow of air to the lungs.

Acne

A

cne is a skin disease that occurs in adolescents. The over-activity of oil glands at the base of a hair follicle causes acne. Acne can take many forms, such as whiteheads, blackheads, pimples, and cysts.

• Acne is more prevalent in women than men. • Factors that may contribute to acne in women include: hormonal fluctuations of menstrual cycles and use of cosmetics. • There are two classes of acne, noninflammatory (blackheads and whiteheads), and inflammatory (papules, pustules, and cysts). • Acne can cause psychological problems. • There is no cure for acne. There are only treatments that prevent and control breakouts. • Chocolate and greasy foods do not cause acne. • In acne, too much sebum is produced by the over-stimulated sebaceous glands. • Hormones are known to be the main culprit for acne. • The full cycle of acne generally lasts about 8 weeks. • Laser therapy, chemical peels, dermabrasion, and other treatments have been suggested for acne scarring.

Inflammatory Acne The papule is a small, solid, usually inflammatory elevation of the skin that does not contain pus. Hormonal Changes Acne is caused due to changes in hormones during the menstrual cycle.

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Cancer

C

ancer is the uncontrolled growth of cells. Cancerous cells can spread in any tissue of the body. Cancer is a class of diseases that can affect people of all ages. It is one of the main causes of death in many countries.

Treatment of Cancer Cancer can be treated by surgery, chemotherapy, and radiotheraphy. Cancer is Curable Cancer risk can be reduced by not smoking, eating healthy food, and avoiding contact with carcinogens.

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• More than 11 million people across the world are affected by cancer. Cancer causes 12.5% deaths every year worldwide. • Common types of cancer are leukemia, breast and ovarian cancer in women, prostate cancer in men, and cancer of lungs, colon, rectum, kidney, skin, head, and neck. • Infectious diseases and exposure to chemicals can lead to cancer. • The disease tends to affect older people – but can strike at any time. • Cancer happens when a tiny part of the cell’s mechanism goes wrong. • The key symptom of lung cancer is a persistent cough that gradually gets worse. • Leukemias and lymphomas are cancers which affect the cells that are part of the fluids circulating around the body.

HIV

H

IV or Human Immunodeficiency virus is a retrovirus. HIV causes AIDS or Acquired Immunodeficiency Syndrome. This virus attacks the human immune system. Viruses are nucleic acid wrapped in a layer of protein. They spread from one person to another through coughs, sneezes, vomit, or contact with body fluid of an infected person.

• HIV spreads through unprotected sex, transfusions of unscreened blood, contaminated needles, and from an infected woman to her child during pregnancy, childbirth, or breastfeeding. • A blood test for HIV is the only way to test for the virus. • HIV is most frequently transmitted sexually.

HIV Causes AIDS In 1984 scientists proved that HIV causes AIDS. The first reported case of AIDS was in the United States in 1981.

Medicine for AIDS AIDS cannot be cured but with the new medications and protease inhibitors available, people can live longer.

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Index Antigens 19, 21

Pathogens 19

Autoimmune 19

Pituitary 49, 53

Axial 6, 12

Platelets 23

Carcinogens 62

Restriction enzymes 48

Cardiac 12, 25

Retina 27

Cerebrum 15

Sperm 42, 43

Coronary 22

Thalamus 15

Cysts 61

Trachea 29, 32, 33

Dendrites 17

Uracil 51

Dialyzer 55

Urethra 34

Diaphragm 9, 31, 33 Duodenum 40 Endocrine 3, 5, 35, 40, 49, 53 Epithelial 4 Gestation 44 Gregor Mendel 45 Heinrich Wilhelm Gottfried 17 Hepatic 39 Keratin 10 Lumen 24 Lymphatic 5, 19 Mastication 8 Meninges 16 Neurons 4, 14, 17, 18 Nucleotides 46, 50, 51 Parasites 21 Parotid gland 57

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