HUMAN BODYBody Parts

Bone & Muscles

HUMAN BODY

HUMAN HEART

Organ that pumps blood, circulating it to all parts of the body

The human heart is a four-chambered double pump with its right and left sides fully separated by a septum and subdivided on both sides into an atrium above and a ventricle below. The right atrium receives venous blood from the superior and inferior venae cavae (see vena cava) and propels it into the pulmonary circulation. The left atrium takes in blood from the pulmonary veins and sends it into the systemic circulation. Electrical signals from a natural pacemaker cause the heart muscle to contract. Valves in the heart keep blood flowing in one direction. Their snapping shut after each contraction causes the sounds heard as the heartbeat. See also cardiovascular system.

STRUCTURE OF HUMAN HEART

Structure of the human heart. Oxygen-rich blood from the lungs enters the heart through the pulmonary veins, passing into the left atrium and on to the left ventricle. Contraction of the muscles of the left ventricle forces blood into the aorta. The mitral valve prevents blood from moving back into the left atrium during contraction. Various arteries branch off from the aorta to supply blood to all parts of the body. Oxygen-poor blood draining from the body into the superior vena cava and inferior vena cava flows to the right atrium, through the tricuspid valve, and into the right ventricle. As the right ventricle contracts, oxygen-poor blood passes through the pulmonary valve into the pulmonary arteries and on to the lungs to receive oxygen.

CIRCULATIONProcess by which nutrients, respiratory gases, and metabolic products

are transported throughout the body.

In humans, blood remains within a closed cardiovascular system composed of the heart, blood vessels, and blood. Arteries carry blood away from the heart under high pressure exerted by the heart's pumping action. Arteries divide into smaller arterioles, which branch into a network of tiny capillaries with thin walls across which gases and nutrients diffuse. Capillaries rejoin into larger venules, which unite to form veins, which carry blood back to the heart. (See artery; capillary; vein.) The right and left heart chambers send blood into separate pulmonary and systemic circulations. In the first, blood is carried from the heart to the lungs, where it picks up oxygen and releases carbon dioxide; in the second, blood is carried between the heart and the rest of the body, where it carries oxygen, nutrients, metabolic products, and wastes.

CIRCULATIONHuman circulatory system. Oxygen-rich blood is shown in red, oxygen-poor blood in blue. The pulmonary circulation consists of the right ventricle and the exiting pulmonary artery and its branches, the arterioles, capillaries, and venules of the lung, and the pulmonary vein. Unlike the other arteries and veins, the pulmonary arteries carry deoxygenated blood and the pulmonary veins carry oxygenated blood. The aorta arises from the left ventricle. The brachiocephalic artery arises from the aorta and divides into the right common carotid and right subclavian arteries. The left and right common carotids extend on either side of the neck and supply much of the head and neck. The left subclavian artery (arising from the aorta) and the right subclavian artery supply the arms. In the lower abdomen, the aorta divides into the common iliac arteries, which give rise to external and internal branches supplying the legs.

LUNGSEither of two light, spongy, elastic organs in the chest, used for

breathing.

Each is enclosed in a membrane (pleura). Contraction of the diaphragm and the muscles between the ribs draw air into the lungs through the trachea, which splits into two primary bronchi, one per lung. Each bronchus branches into secondary bronchi (one per lobe of lung), tertiary bronchi (one per segment of lung), and many bronchioles leading to the pulmonary alveoli. There oxygen in the inspired gas is exchanged for carbon dioxide from the blood in the surrounding capillaries. Adequate tissue oxygen supply depends on sufficient distribution of air (ventilation) and blood (perfusion) in the lungs. Lung injuries or diseases (e.g., emphysema, embolism, pneumonia) can affect either or both.

RESPIRATORY SYSTEM

In humans, the diaphragm and, to a lesser extent, the muscles between the ribs generate a pumping action, moving air in and out of the lungs through a system of pipes (conducting airways), divided into upper and lower airway systems. The upper airway system comprises the nasal cavity (see nose), sinuses, and pharynx; the lower airway system consists of the larynx, trachea, bronchi, bronchioles, and alveolar ducts (see pulmonary alveolus). The blood and cardiovascular system can be considered elements of a working respiratory system. See also thoracic cavity.

As air enters the nasal cavity through the nostrils, it is warmed and moistened by mucous membranes of the nasal turbinates before entering the pharynx. Stiff hairs lining the vestibule inside the nostrils help filter the entering air. The air-filled sinuses adjacent to the nasal cavity produce mucus. The larynx connects the pharynx with the trachea or windpipe. The cartilaginous epiglottis prevents food from entering the larynx during swallowing. A left and right primary bronchus supply each lung with air from the trachea. They divide into smaller secondary and tertiary bronchi; the smallest divisions, bronchioles, lead to the cup-shaped, thin-walled alveoli, which occur in clusters (alveolar sacs). Oxygen and carbon dioxide are exchanged between the alveoli and surrounding capillaries. Oblique fissures or grooves of each lung separate the upper lobe from the lower lobe. The horizontal, or transverse, fissure of the right lung forms a middle lobe. Movement of the diaphragm along with the ribs and rib muscles causes expansion and contraction of the lungs during breathing.

DIGESTION

Process of dissolving and chemically converting food for absorption by cells.

In the mouth, food is chewed, mixed with saliva, which begins to break down starches, and kneaded by the tongue into a ball for swallowing. Peristalsis propels it through the esophagus and the rest of the alimentary canal. In the stomach, food mixes with acid and enzymes, which further break it down. The mixture, called chyme, enters the duodenum, the first part of the small intestine. Bile from the liver breaks up fat globules. Enzymes from the pancreas and intestinal glands act on specific molecules, breaking carbohydrates down into simple sugars, proteins into amino acids, and fats into glycerol and fatty acids. These products are absorbed by the bloodstream. Indigestible substances, such as fibre, pass into the large intestine, where water and ions are reabsorbed and feces held for excretion.

DIGESTIVE SYSTEM

Major organs of the human digestive system. Food taken in by the mouth is guided by the tongue as it is sheared and ground by the teeth. The bolus of chewed food is moistened and lubricated with saliva secreted by the salivary glands. Enzymes in the saliva begin the breakdown of starches. The epiglottis, a flap of tissue, prevents food from the pharynx from entering the larynx during swallowing. Muscles in the esophagus wall contract in waves to move the food to the stomach. Gastric juices secreted by the stomach contain a mixture of substances (including enzymes and hydrochloric acid) that break down the food into a semiliquid mass called chyme. The chyme passes into the small intestine, where food molecules are broken down into sugars, amino acids, and fatty acids. These useful substances are absorbed into the bloodstream as the food passes through the duodenum, jejunum, and ileum. The pancreas secretes digestive enzymes into the duodenum. The liver secretes bile salts that make insoluble fats entering the small intestine water-soluble and vulnerable to enzymatic action. Excess bile salts are stored in the gallbladder. The large intestine (colon) serves to remove water and electrolytes from the digested chyme and to compact and store undigestible material, called feces. Fecal matter is moved by muscular contractions into the rectum and expelled from the anus.

LARYNXVoice BoxHollow, tubular structure connecting the pharynx with the

trachea, through which air passes on the way to the lungs.

The larynx consists of a framework of cartilage plates, with a ridge in front (Adam's apple); the epiglottis, a flaplike projection up into the throat that covers the airway during swallowing to keep food and liquid from entering; and the vocal cords, whose vibration produces the sound of the voice

LARYNX STRUCTURE

(A) Frontal view and (B) cutaway side view of the human larynx. The larynx is composed of cartilage plates that are joined together by muscles and ligaments. The thyroid cartilage, the largest, forms a prominence in front called the Adam's apple. The leaf-shaped epiglottis, attached to the upper part of the thyroid cartilage, closes during swallowing. The vocal cords in the cavity of the larynx are large folds in the mucous membrane lining the larynx. They stretch between the thyroid cartilage in front and the arytenoids cartilages in the back. As air passes between them, they vibrate to emit sound.

KIDNEYOne of a pair of organs that maintain water balance and expel

metabolic wastes.

Human kidneys are bean-shaped organs about 4 in. (10 cm) long, in the small of the back. They filter the entire 5-quart (about 4.5-liter) water content of the blood every 45 minutes. Glucose, minerals, and needed water are returned to the blood by reabsorption. The remaining fluid and wastes pass into collecting ducts, flowing to the ureter and bladder as urine. Each kidney has over 1 million functional units (nephrons) involved in the process of filtration and reabsorption. The kidneys also secrete renin, an enzyme involved in blood pressure regulation. Disorders include kidney failure, kidney stones, and nephritis

KIDNEY STRUCTURE

Cross section of a kidney. The kidney is made up of an outermost cortex, a middle medulla, and an inner pelvis. Blood enters via the renal artery, which branches into smaller vessels, each of which terminates in a tuft of capillaries (glomerulus). Fluids from the blood are forced out of the glomerulus into the surrounding Bowman's capsule during filtration. The glomerulus, Bowman's capsule, and associated renal tubule make up the nephron. Any important substances filtered from the blood (including glucose, minerals, and much of the water) are returned to it by reabsorption in the renal tubule. The medulla is divided into conical masses of tissue (renal pyramids) that contain the collecting ducts for the fluid (urine) not reabsorbed into the blood. Water is further removed from the urine as it passes through the collecting ducts into the funnel-shaped renal pelvis, which leads to the ureter.

URINARY SYSTEM

System that produces and discharges urine to rid the body of waste products.

It consists of the kidneys, which balance electrolytes in blood, retaining and adding needed ones and removing unneeded or dangerous ones for excretion; the ureters, two thin muscular tubes 10–12 in. (25–30 cm) long that move the urine by peristalsis; the hollow, muscular bladder, which receives and stores it; and the urethra, through which it leaves the body. In women the urethra is 1.5 in. (4 cm) long. In men it is longer (since it passes through the penis), about 8 in. (20 cm), and carries semen from the prostate gland as well as urine. Urinary disorders, which can lead to dehydration or edema and to a dangerous buildup of waste and toxic substances, include kidney failure, tumours, and bladder and kidney stones.

ENDOCRINE SYSTEMGroup of ductless glands that secrete hormones necessary for normal

growth and development, reproduction, and homeostasis.

The major endocrine glands are the hypothalamus, pituitary, pineal, thyroid, parathyroids, adrenals, islets of Langerhans in the pancreas, ovaries, and testes. Secretion is regulated either by regulators in a gland that detect high or low levels of a chemical and inhibit or stimulate secretion or by a complex mechanism involving the hypothalamus and the pituitary. Tumours that produce hormones can throw off this balance. Diseases of the endocrine system result from over- or underproduction of a hormone or an abnormal response to a hormone.

ENDOCRINE SYSTEM, HUMAN: MAJOR GLANDS OF THE HUMAN ENDOCRINE SYSTEMMajor glands of the human endocrine system. The hypothalamus stimulates the pituitary gland and influences food intake, weight regulation, fluid intake and balance, thirst, body heat, and the sleep cycle. Pituitary hormones stimulate growth, egg and sperm development, milk secretion, and release of hormones by other glands. The pineal gland may play a significant role in sexual maturation and the circadian rhythm. Thyroid hormones regulate the metabolic rate of tissues, stimulate the contraction of heart muscle, and are necessary for normal growth and brain development before birth and during infancy. Parathyroid hormone regulates calcium, phosphorus, and magnesium levels. The adrenal glands regulate salt and water retention, some reactions of the immune system, and blood pressure. The islets of Langerhans regulate blood sugar levels. The ovaries and testes produce hormones that regulate the reproductive system and that produce male and female secondary sex characteristics.

Bones of Human Body

THE BRAINConcentration of nerve tissue in the front or upper end of a body.

It handles sensory information, controls motion, is vital to instinctive acts, and in higher vertebrates is the centre of learning. Vertebrate brains consist of the hindbrain (rhombencephalon), midbrain (mesencephalon), and forebrain (prosencephalon). The hindbrain comprises the medulla oblongata and the pons, which connects the spinal cord with higher brain levels and transfers information from the cerebral cortex to the cerebellum. The midbrain, a major sensory integration centre in other vertebrates, serves primarily to link the hindbrain and forebrain in mammals. Large nerve bundles connect the cerebellum to the medulla, pons, and midbrain. In the forebrain the two cerebral hemispheres are connected by a thick bundle of nerve fibres (corpus callosum) and are divided by two deep grooves into four lobes (frontal, parietal, temporal, and occipital). The cerebrum, the largest part of the human brain, is involved with its more complex functions. Motor and sensory nerve fibres from each hemisphere cross over in the medulla to control the opposite side of the body.

Side view of the brain showing its major structures. The large cerebrum is divided into two halves, or hemispheres, connected by the corpus callosum, a band of nerve fibres. Two grooves divide the hemispheres into four lobes: frontal, temporal, parietal, and occipital. Many nerve cells are found in the convoluted cerebrum's outer surface, or cerebral cortex, which controls sensory and motor activities. The thalamus relays incoming sensory impulses from the spinal cord to the cortex. The hypothalamus's many functions include control of breathing, blood flow, temperature regulation, and emotions. The pituitary gland is attached to and regulated by the hypothalamus. The midbrain relays signals between the forebrain and hindbrain. The cerebellum, along with the cerebrum, plays a role in voluntary movement as well as balance. The pons serves as a relay point linking the medulla oblongata, midbrain, cerebellum, and cerebrum. The medulla, lying between the pons and the spinal cord and continuous with both, plays a role in essential involuntary regulatory and reflexive responses (including breathing, swallowing, and heartbeat) and relays signals between the spinal cord and other brain regions

PARTS OF BRAIN

1. Cerebrum : Largest part of the brain.

The two cerebral hemispheres consist of an inner core of myelinated nerve fibres, the white matter, and a heavily convoluted outer cortex of gray matter (see cerebral cortex). Nerve fibres in the white matter connect functional areas of the cortex in the same hemispheres, connect functional areas of the cortex in opposite hemispheres, and connect the cerebral cortex to lower centres (e.g., the spinal cord). A front-to-back fissure divides the cerebrum's two hemispheres. Each hemisphere controls the opposite side of the body. The corpus callosum, a thick band of white matter, connects them, allowing integration of sensory data and responses from both sides of the body. Other important cerebral structures include the hypothalamus and the thalamus.

2. Cerebellum

Part of the brain that integrates sensory input from the inner ear and from proprioceptors in muscle with nerve impulses from the cerebrum (see cerebral cortex), coordinating muscle responses to maintain balance and produce smooth, coordinated movements.

Located below the cerebral hemispheres and behind the upper medulla oblongata and pons, each of its two connected hemispheres has a core of white matter within a cortex of gray matter. Disorders usually produce neuromuscular disturbances, in particular ataxia.

EYES

Organ that receives light and visual images.Non-image forming, or direction, eyes are found among worms, mollusks, cnidarians, echinoderms,

and other invertebrates; image-forming eyes are found in certain mollusks, most arthropods, and nearly all vertebrates. Arthropods are unique in possessing a compound eye, which results in their seeing a multiple image that is partially integrated in the brain. Lower vertebrates such as fish have eyes on either side of the head, allowing a maximum view of the surroundings but producing two separate fields of vision. In predatory birds and mammals, binocular vision became more important. Evolutionary changes in the placement of the eyes permitted a larger overlap of the two visual fields, resulting in the higher mammals in a parallel line of direct sight. The human eye is roughly spherical. Light passes through its transparent front and stimulates receptor cells on the retina (cones for colour vision, rods for black-and-white vision in faint light), which in turn send impulses through the optic nerve to the brain. Vision disorders include near- and farsightedness and astigmatism (correctable with eyeglasses or contact lenses), colour blindness, and night blindness. Other eye disorders (including detached retina and glaucoma) can cause visual-field defects or blindness

1. EYES-STRUCTURE

Structure of the human eye. The outer portion consists of the white protective sclera and transparent cornea, through which light enters. The middle layer includes the blood-supplying choroid and pigmented iris. Light passing into the interior through the pupil is regulated by muscles that control the pupil's size. The retina comprises the third layer and contains receptor cells (rods and cones) that transform light waves into nervous impulses. The lens, lying directly behind the iris, focuses light onto the retina. The macula lutea, in the centre of the retina, is a region of high visual acuity and colour discrimination. Nerve fibres pass out through the optic nerve to the brain's visual centre. The eye's anterior and posterior chambers contain a watery fluid that nourishes the cornea and lens. The vitreous humour helps maintain the eye's shape. A thin layer of mucous membrane (conjunctiva) protects the eye's exposed surface. External muscles, including the medial rectus and lateral rectus muscles, connect and move the eye in its socket.

TOOTHAny of the hard structures in the mouth used for biting and chewing and in

speech.

Each consists of a crown above the gum and one or more roots below it, embedded in the jaw. Its inner pulp contains the blood and nerve supply for the bonelike dentin, covered in the crown by enamel, the hardest tissue in the body. Twenty primary (baby) teeth come in by age 2 1/2 and fall out between ages 5 and 13 to be replaced by 32 permanent teeth. The incisors, in front, are shaped mostly for biting, the pointed canines for tearing, and the premolars and molars for grinding food. The teeth are subject to caries (decay), caused by acid from bacteria in plaque, a yellowish film that builds up on teeth. Misalignment of teeth between the upper and lower jaws can grind down the teeth and cause problems in chewing. Elsewhere, it is a cosmetic problem. Both can be treated with braces

STRUCTURE OF TOOTHCross section of an adult molar. The crown (the part of the tooth above the gum) is protected by a hard outer layer of enamel. The roots sit in a socket in the jawbone and are covered with cementum, a bonelike material. The periodontal ligament anchors the cementum in the jaw and cushions the tooth from the pressures of chewing. The tooth's main portion, the dentin, surrounds the soft pulp, which carries the blood vessels and nerves. Specialized cells of the pulp project threadlike extensions into the dentin through narrow channels and serve to form new dentin from minerals in the blood.

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Name : MUKUL

Class : X ‘B’

K.V.S sec-14 Gurgaon

Second shift