tag:blogger.com,1999:blog-68517756509963423022024-03-06T12:02:14.215-08:00Science, Biology,Human and Body Parts Best InformationIN THIS WEBSITE YOU CAN LEARN ABOUT Science, Biology,Human and Body Parts Best InformationAnonymoushttp://www.blogger.com/profile/07906956283015793204noreply@blogger.comBlogger20125tag:blogger.com,1999:blog-6851775650996342302.post-72449918208203906742013-10-10T01:40:00.001-07:002013-10-10T01:41:38.727-07:00The Nervous System<div dir="ltr" style="text-align: left;" trbidi="on">
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<tr><td class="tr-caption" style="text-align: center;">The Nervous System</td></tr>
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A complete understanding of the human nervous system remain s a challenge. Several billion cells remain associated with this system. The varying functions of these cells and the nervous system are responsible for human behaviour and activities. Hence, scientists from different fields collectively are interested in understanding the functioning of this system. Studies on brain and other related structures began several years ago. Even to-day thousands of scientists are involved in researches for knowing the structure and functioning of the brain. For a thorough knowledge of this system, further works in anatomy, physiology, molecular,biology, psychology, medicine and other related fields are needed. Basically the nervous system is formed of nerve cells or neurons. Neurons are responsible for transmission of impulses. They also help in realising, analysing and storing messages. They can stimulate muscles to work. The network of interconnected neurons in the nerves, brain and spinal cord have highly complicated ethods of functioning. A neuron has a basic cell structure called the cyton. The projections of the cyton are the dendrites and the dendrons. The inter communicating long projection is the axon. There are variations in the shape of the cyton, number of dendrons and nature of axon. A neuron is interconnected with the dendrite of the neighbouring neuron through the endplate of the axon. Such specialized connections are called as synapses. In the terminal regions of the effector nerves the axon of the nerve cells are in contact with the muscle tissue. These joints are named as neuro - muscular junctions.<br />
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<b>The structure of a peripheral nerve :</b><br />
A nerve is made up of several nerve fibres. A nerve fibre contains axons with their coverings called schwann cells. The fibres are grouped into fasciculi. The number and pattern of fasciculi vary in different nerves. Thus a nerve trunk possesses many such fasciculi. Such a trunk is surrounded by an epineuruium. The individual fasciculi are enclosed by a multilayered perineurium. The perineurium surrounds the endoneurium or intra fascicular connective tissue. In a peripheral nerve the epineurium constitutes 30 -70 % of the total cross sectional area of the nerve bundle. The thickness is more when there are more fasciculi. A layer of fat in the epineurium provides a ‘cushion’ effect to the nerve. The perineurium contains alternating layers of flattened polygonal cells. The endoneurium remains condensed around axons. The components of the endoneurium remain bathed in endoneurial fluid. The fasciculi of the nerve are supplied blood by vasa nervosum. These minute blood vessels radiate upto the endoneurium.<br />
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<b>Nervous System</b><br />
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The organs of the nervous system are continuous in nature. However,for study purposes it can be divided into systems and organs.<br />
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<b>A. Central Nervous System (C N S)</b><br />
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This system includes the brain and the spinal cord or medulla spinalis. They are protected by surrounding bones. While the brain is located within the cranium, the spinal cord is placed within the vertebral canal of the vertebrae. Through an opening called foramen magnum, the spinal cord descends down from the brain.<br />
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<b>B. Peripheral Nervous System.</b><br />
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It consists of nerves and ganglia. The nerves that are formed from the brain are called the cranial nerves. There are 12 pairs of cranial nerves and 31 pairs of spinal nerves.<br />
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<b>C. Autonomous Nervous System.</b><br />
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The nerves in this system transmit impulses from the C N S to smooth muscles, cardiac muscles and glands. It is also called the involuntary nervous system. It is subdivided into sympathetic and parasympathetic divisions.<br />
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Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-6851775650996342302.post-85010949142483022192013-09-15T03:54:00.002-07:002013-09-15T03:54:22.170-07:00Tonsils<div dir="ltr" style="text-align: left;" trbidi="on">
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These are the largest lymph nodules. They provide protection against bacteria and other harmful materials. In adults the tonsils decrease in size and may disappear. There are 3 groups of tonsils in the pharyngeal walls. Of the three, the palatine tonsils are usually refered to as “the tonsils”. These are larger lymphoid masses on each side of the junction between the oral cavity and the pharynx. The pharyngeal tonsil or adenoid are found near the junction between the nasal cavity and the pharynx. The lingual tonsil is a loosely associated collection of lymph nodules on the posterior surface of the tongue.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-38680942703394531802013-09-15T03:52:00.004-07:002013-09-15T03:52:51.594-07:00Spleen<div dir="ltr" style="text-align: left;" trbidi="on">
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The lymph enters the lymph nodes through afferent lymphatic vessels and exits through efferent vessels. The nodes contain open spaces called sinuses. The sinuses are lined with phagocytic cells. Spleen It is roughly the size of a clenched fist. It is located on the left side of the abdominal cavity. It has a fibrous capsule. The spleen contains two types of lymphatic tissues, namely the red pulp and the white pulp.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-90713753767911639912013-09-15T03:51:00.001-07:002013-09-15T03:51:11.594-07:00Lymph nodes<div dir="ltr" style="text-align: left;" trbidi="on">
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<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small; text-align: left;">Lymph nodes</span></td></tr>
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These are small round structures. Their size ranges from 1-25 mm. They are distributed throughout the course of the lymphatic vessels. These nodes are found all over the body. However they are concentrated as aggregations in 3 regions of the body. These are the inguinal nodes in the groin, the axillary nodes in the axillary region and the cervical nodes of the neck.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-56689760513128155222013-09-15T03:49:00.003-07:002013-09-15T03:49:36.941-07:00Thymus Gland<div dir="ltr" style="text-align: left;" trbidi="on">
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It is a roughly triangular, bilobed gland. It is located in the mediastinum (ie., between the lungs). It lies between the sternum and the pericardium. Its size varies with age. It is largest in the early part of life (upto 15 years). At birth it weighs 10 - 15 g. After puberty it greatly decreases in size. Each thymus lobe is surrounded by a thin capsule made of the connective tissue. It has 2 layers. The inner layer is the medulla, the outer layer is cortex. The lymphocytes are found only in cortex layer.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-1775320112348316522013-09-15T03:33:00.001-07:002013-09-15T03:46:49.125-07:00Lymphatic System<div dir="ltr" style="text-align: left;" trbidi="on">
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<tr><td class="tr-caption" style="text-align: center;">Lymphatic System</td></tr>
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Lymphatic circulation along with blood circulation plays a key role in maintaining the fluidity in all regions of the body. It helps to maintain fluid balance in tissues and it absorbs fat from the digestive tract. It also functions as body’s defence system against micro organisms and other harmful substances. This system includes lymph, lymphocytes, lymphatic vessels, lymph nodules, lymph nodes, tonsils, the spleen and the thymus gland.<br />
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<b>Lymphoid Cells And Tissues </b>:<br />
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Lymphatic organs contain lymphatic tissues.These tissues primarily consist of lymphocytes. They also contain macrophages, dendritic cells and reticular cells. Lymphocytes are a type of white blood cells. They originate from red bone marrow and are carried by blood to lymphatic organs and other tissues. There are several classes of lymphocytes. The B-lymphocytes or B cells synthesize antibodies for recognizing and neutralising alien macromolecules. T- lymphocytes can recognize and selectively kill cells infected with viruses. B and T lymphocytes are produced from stem cells present in the bone marrow. The T lymphocytes get matured only after entering into Thymus, a lymphoid organ through circulation. Maturation and differentiation of B cells will occur in the bone marrow itself. Thus the thymus and bone marrow are described as central or primary lymphoid organs.<br />
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<b>The Lymphatic Circulation :</b><br />
The lymph fluid from the tissues is drained by lymphatic capillaries. These capillaries though present in many tissues are absent in epidermis, hairs, nails, cornea, cartilages, CNS and bone marrow. The lymphatic capillaries join into larger vessels. The larger vessels pass to local or remote lymph nodes. These vessels and associated lymph nodes are arranged in regional groups. Each group has its region of drainage. Nodes within a group are interconnected. Such regional groups with nodes and vessels are organised in (1) Head and neck (2) Upper limbs (3) Lower limbs (4) Abdomen and pelvis (5) thorax. The regional vessels return to the venous blood circulation via the right and left lympho venous portals. Nearly eight lymphatic trunks converge at the site of the vertebral column and open into the venous portal nearer to the neck.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-83634527656558342632013-09-15T03:24:00.002-07:002013-09-15T04:01:13.220-07:00Blood Vessels <div dir="ltr" style="text-align: left;" trbidi="on">
<b>Structure of blood vessels<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
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<tr><td class="tr-caption" style="text-align: center;">Blood Vessels</td></tr>
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The blood vessels show a vast range of structural modifications. However a few basic patterns can be studied. A blood vessel consists of a wall and a lumen or cavity. The wall of the blood vessels is made up of 3 distinct layers or tunica. They are the tunica intima, tunica media and tunica externa or tunica adventitia. The tunica intima is formed of an endothelium, a delicate connective tissue and elastic fibres. The tunica media contains smooth muscle cells. It causes vasoconstriction and vasodilation. The tunica externa is composed of connective tissue. The composition and thickness of layers varies with the diameter of the blood vessels and the type.<br />
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<b>Types of blood vessels :</b><br />
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<b>1. Large elastic arteries :</b><br />
The walls of these arteries contain elastic fibres. The smooth wall measures about 1micron in thickness. It gets stretchedunder the effect of pulse and recoils elastically<br />
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<b>2. Muscular arteries :</b><br />
There are larger and smaller muscular arteries. The larger muscular arteries are inelastic and they have thick walls. The wall has 30-40microns in diameter in the layers of smooth muscles. Since they regulate blood supply, they are called distributing arteries. The small muscular arteries are capable of vasodilation and vasoconstriction.<br />
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<b>3. Arterioles :</b><br />
They conduct blood from the arteries to the capillary bed. These are small vessels capable of vasodilation and vasoconstriction.<br />
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<b>4. Capillaries :</b><br />
These are fine vessels found between arterioles and venules. They measure 5-8micron in diameter.<br />
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<b>5. Venules :</b><br />
These are tubes of flat, oval or polygonal endothelial cells. Each venule is formed by the convergence of two or more capillaries. Its diameter ranges upto 30micron.<br />
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<b>6. Veins : </b><br />
Veins seen in anatomy are medium veins. They run in between venules and large veins. Large veins transport blood to the heart. Veins with diameter above 2 mm have valves. They are of semilunar type. They allow movement of blood towards the heart. There are several valves in the medium veins.<br />
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<b>Branching of blood vessels :</b><br />
When an artery divides into two equal branches, the original artery ceases to exist. Hence the branches are called terminal branches. The smaller branching vessels formed on the sides are called the collateral branches. When arteries are joined to each other it is named as anastomosis.<br />
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<b>Blood supply to blood vessels </b>:<br />
As any other region, the cells and tissue on the wall of the blood vessel require nourishment. Some amount can diffuse from blood in the lumen. For vessels having diameter greater than 1 mm, diffusion of nutrients may not be possible. Such vessels have very minute vessels called vasa vasorum spread over them. They penetrate into the wall of the blood vessels.<br />
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<b>Innervation of blood vessels :</b><br />
The walls of the blood vessels are innervated by sympathetic nerve fibres. They regulate the contraction of the musculature. They effect vasoconstriction.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-81795957824415552902013-09-11T05:11:00.004-07:002013-09-15T03:58:44.118-07:00Portal Circulation<div dir="ltr" style="text-align: left;" trbidi="on">
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In the systemic circulation the venous blood passing through spleen, pancreas, stomach and interstine is not carried back directly to the heart. It passes through the hepatic portal vein to the liver. This vein begins as capilaries from the visceral organs and ends in the liver again as capillaries. These capillaries converge to form the hepatic vein which joins the inferior vena cava, conveying blood to right atrium. This route is the portal circulation. Components of Circulatory system Blood vessels The blood vessels carrying blood away from the heart are the arteries.<br />
The Veins carry blood towards the heart. The arteries and veins are named and classified according to their anatomical position. They can also be classified according to their size and wall structure. Functionally, arteries are subdivided into conducting, distributing and resistance vessels.<br />
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<b>1. Conducting vessels :</b><br />
These are large arteries from the heart and their main branches. the walls of these vessels are elastic in nature.<br />
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<b>2. Distributing vessels : </b><br />
These are smaller arteries reaching individual organs. They branch into the organs. They have muscular walls.<br />
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<b>3. Resistance vessels :</b><br />
These are mostly arterioles. While these vessels are smaller, their walls are highly muscular. Hence these vessels can reduce pressure of blood due to peripheral resistance.<br />
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<b>4. Exchange vessels :</b><br />
These are the capillaries. The walls of these vessels allow exchanges between blood and the tissue fluid surrounding the cells. The substances commonly exchanged are oxygen, carbon-di-oxide, nutrients, water, inorganic ions, vitamins, hormones, metabolic products and antibodies.<br />
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<b>5. Capacitance or reservoir vessels :</b><br />
These are the larger vessels and veins. These are of varying sizes. They collect and convey blood back to the heart. The higher capacitance of these vessels is due to their distensibility. Hence their blood content is more, even at low pressure. The number of such veins is also enormous.. Thus the veins are called as the “blood reservoirs”<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-37461863581331420562013-09-11T05:03:00.000-07:002013-09-11T05:04:09.297-07:00The Circulatory System <div dir="ltr" style="text-align: left;" trbidi="on">
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<tr><td class="tr-caption" style="text-align: center;"><b style="font-size: medium; text-align: left;">Circulatory System </b></td></tr>
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The multicellular organisation in animal world has resulted in the origin and evolution of circulatary system in animals. This arrangement facilitates internal transport of various substances to all organs and organ systems.Among majority of multicellular animals this system remains as a closed type. It has blood running inside closed blood vessels, the blood being pumped by heart. In man, as in all mammals there is a double circulation of blood. The primary circulation through pumping action of heart, supplies blood to all regions of the body. The blood later returns to the heart. It is called the systemic circulation or body circulation. A similar circulation carries blood to lungs for oxygenation and returns it back to the heart. It is called the pulmonary circulation. Systemic and Pulmonary circulations The most important component of this system is the heart. It is alarge, muscular, valved structure having four chambers. The chambers are the right atrium, left atrium, right ventricle and left ventricle. Each atrium opens into a corresponding ventricle. The right and left chambers are separated by septa.<br />
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<b>Systemic circulation :</b><br />
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The left atrium receives oxygenated blood from the lungs, through the pulmonary vein. When the atria contract, blood from the left atrium is forced into the left ventricle. Later by a contraction of the ventricle, the blood leaves the heart through the aorta. The aorta is the single systemic artery emerging from the heart. By successive branchings, the aorta gives rise to hundreds of arteries taking blood to all regions of the body. As the branchings happen, the arteries divide into numerous (4 × 106 ) arterioles. Inthe target organs they produce four times as many capillaries. A similar number of venules converge into each other forming veins of increasingly larger size. Finally, only two veins, the superior and inferior vena cavae return the blood to the right atrium. Thus the course of blood from left ventricles through the body organs and back to the atrium forms the systemic circulation. Pulmonary circulation :- The venous blood from right atrium is conducted to the right ventricle. The ventricle expels the blood via the pulmonary trunk to he lungs. The oxygenated blood later returns by the pulmonary veins to the left atrium. This circulation from right ventricle to the left atrium via the lungsis termed the pulmonary circulation<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-48236791534751718162013-09-07T05:24:00.003-07:002013-09-07T05:24:50.605-07:00Respiratory System<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
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The process of respiration involves movement of air in and out of the lungs, gas exchange between air in lungs and the blood, transport of O2and CO2.These processes are facilitated by working together of well developed respiratory organs and the circulatory system. The respiratory organs include nasal cavity, pharynx, larynx, trachea, bronchi and lungs. These organs are organised into upper and lower respiratory tracts. Upper respiratory tract.<br />
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<b>1. Nasal cavity :</b><br />
The nasal cavity follows the external nose. The nose is a visible prominent structure. Internally it is supported by cartilage plates. The bridge of the nose is formed of the nasal bones and extension of the skull bones(frontal and maxillary). The respiratary passage is divided into two chambers by a median partition. The nasal passage opens to the outside throughexternal nostrils. It opens inside by internal nostrils at the pharynx.<br />
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<b>2. Pharynx : </b><br />
The buccal cavity and the nasal passage open into the pharynx. It is a common pathway that opens into the oesophagus of the alimentary canal and larynx of the respiratory system. The pharynx is divided into three regions, namely the nasopharynx, the oropharynx and the laryngopharynx.The nasopharynx extends from the internal nostril to the region of the uvula. The uvula is a soft outgrowth hanging in between the posterior part of the oral cavity and the pharynx. It prevents the entry of food into the nasal cavity. The wall of the nasopharynx is lined by ciliated columnar epithilium. The middle ear opens into the nasopharynx through two auditory tubes. This arrangement is meant for equalizing the air pressure between the atmosphere and the middle ear. The inner surface of the nasopharynx also contains the pharyngeal tonsil or adenoid meant for defence against infections. An enlargement of the tonsil can interfere with breathing. The oropharynx remains between the uvula and the epiglottis. The oral cavity opens into the oropharynx. Near the opening of the oral cavity 2 sets of palatine tonsils and lingual tonsils are present. The laryngopharynx extends in between the epiglottis and the oesophagus.<br />
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<b>3. Larynx : </b><br />
The larynx is seen just behind the pharynx and the buccal cavity. This region is surrounded by cartilages(3 unpaired and 6 paired). These are interconnected by muscles and ligaments. The unpaired cartilages are the thyroid, cricoid and epiglottis. The thyroid cartilage is the largest. It is also known as the Adam’s apple. The cricoid cartilage forms the base of the larynx. The other cartilages are placed above the cricoid. The epiglottis is attached to the thyroid. It projectsas a free flap over the opening of the larynx. It prevents food particles from saentering into the tracheal tube. The ligaments inside the larynx form the vocal folds or vocal cords. The vocal cords and the openings between them are called the glottis. The vocal cords are involved with sound production. The air moving past the vocal cords make them to vibrate. Louder sounds are made by increasing the amplitude of vibrations. Frequency of the vibrations can be altered by changing the length of the vibrating segments of the vocal c rds. The length is altered by muscles attached to the cartilage. Males usually have longer vocal cords than females. The sound made by the vocal cords can be altered by the tongue, lips and teeth to form words.<br />
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<b>4. Trachea (or wind pipe) </b><b>:</b><br />
It is a membranous tube. The wall is made up of connective tissue and smooth muscles. The wall is provided support by 15-20 ‘C’ shaped cartilage rings. They protect the trachea and keep it open all the time. The inner wall of the trachea is lined by mucous membrane. It consists of ciliated columnar epithelium. The cilia of this epithelium help to propel mucus and foreign particles towards the larynx. The length of the trachea is 10-12 cm. Its inner diameter is 12 mm. The trachea extends from the larynx to the level of the 5th thoracic vertebra. The basal part of the trachea divides to form 2 smaller tubes called the primary bronchi (sing : bronchus). The cartilage ring found at the basal region is called the carina. Foreign objects reaching carina stimulate a powerful cough reflex.<br />
5. Lungs : The pair of lungs are the actual organs of respiration. Each lung is conical in shape. The base of the lung rests on the diaphragm. The right lung is larger than the left and it weighs around 620g. The left lung weighs 560g. The right lung has three lobes and the left lung has two. The lungs are placed within the thoracic cavity. Each lung is surrounded by separate pleural membrane. The region inside the pleural membrane is named as the pleural cavity. This cavity is filled with pleural fluid. The region in between the two lungs is named as the mediastinum. It is a midline partition, being occupied by the heart, trachea and oesophagus. Structures such as the primary bronchi, blood vessels, nerves and lympatic vessels enter or exit the lungs at a specific region on the inner margin of the lungs. This region is known as the hilum. All structures passing through the hilum are referred to as the root of the lung. The primary bronchi on entering into each lung divide further into secondary bronchi. There are two secondary bonchi in the Left lung and three in the rightlung. The secondary bronchi inturn give rise to tertiary bronchi. They divide still further and finally give rise to bronchioles. The diameter of the bronchioles is less than 1 mm. These bronchioles divide several times to become still smaller terminal bronchioles. Like the trachea, the primary bronchi are supported by ‘C’. shaped cartilages and smooth muscles. As the bronchi become smaller the cartilages are replaced by smooth muscles. The terminal branchioles end in small air filled chambers called alveoli. The alveoli are thin walled pouches. They collectivelly provide the respiratory surface for gaseous exchange. The wall of the alveolus is very thin providing a minimal barrier to gaseous exchange between air and blood. The thickness of the wall of the alveolus is as little as 0.05m. Studies have shown that in human lungs there are about 300 million a veoli. They provide a mean total alveolar surface area value of 143 m2.<br />
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Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-6851775650996342302.post-31499801097890747372013-09-05T05:13:00.003-07:002013-09-05T05:20:11.446-07:00Human Digestive system<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
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<tr><td class="tr-caption" style="text-align: center;">Human digestive system</td></tr>
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The process of nutrition in man is holozoic. In this type of nutrition, the nutrients are made available to the body through digestion of food. In digestion, the macromolecules or biopolymers of food are hydrolysed to yield their corresponding monomers. This process is facilitated by enzymes. Thus the digestive system comprises the alimentary canal, associated glands and regions of absorption of food. The digestive tract comprises various organs from mouth to anus. Mouth or Buccal cavity The opening of the oral cavity is bounded by the lips. The lips are muscular folds covered internally by mucosa. The lateral walls of the oral cavity are the cheeks. The inner walls of the cheeks are lined by moist stratified squamous epithelium. The lips and cheeks are useful in the process of mastication and speech.<br />
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<b>Tongue : </b><br />
It is a large muscular organ. It is attached to the floor of the oral cavity. The anerior part of the tongue is free. A thin fold of tissue called the frenulum attaches the free end to the floor of the mouth. The tongue is divided into two parts by a groove called the terminal sulcus. About two thirds of the anterior surface is covered by papillae. Some of them contain taste buds.<br />
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<b>Teeth :</b><br />
There are 32 teeth in the mouth of a human adult. These are called as permanent teeth. There are 4 different types of permanent teeth seen. This nature is known as heterodontism. The types of teeth are incisors(8), canines(4), premolars(8) and molars(12). Since the teeth in the right and left side of the mouth are mirror images of each other, the dental arrangement is represented as follows.<br />
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i 2/2 : c 1/1 : pm 2/2 m 3/3 X 2<br />
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Each tooth consists of three regions. These are the upper crown, middle neck and basal root regions. The crown region has one or more cusps. The tooth is made up of a calcified tissue called dentine. The dentine of the tooth crown is covered by an extremely hard substance called enamel. The surface of the dentine in the root is covered with a bonelike substance called cementum. It helps to anchor the tooth in the jaw. In the centre of the tooth there is a pulp cavity. This cavity is also called as the root canal. This canal contains blood vessels and nerves. The canal opens at the base through apical foramen.<br />
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The teeth are set in sockets along the edges of the upper and lower jaws. This region of the jaw is covered by dense fibrous connective tissue and stratified squamous epithelium. It is called as the gingiva. <br />
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dentine<br />
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1 pulp cavity with nerve and<br />
2 blood vessels<br />
3 root canal<br />
4 apical foramen<br />
5 crown<br />
6 neck<br />
7 root<br />
8 enamel<br />
9 cementum<br />
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<b>Salivary glands :</b><br />
These are scattered throughout the oral cavity. Three pairs of glands are larger. They are the parotid, submandibular and sublingual glands. The Parotid glands are the largest.They are located just anterior to the ear on each side of the head. The submandibular glands are found on the inferior borders of the mandible. The sublingual glands are the smallest. They lie immediatly below the mucous membrane in the floor of the mouth. There are other numerous small, coiled, tubular glands in the mouth. They are the lingual (tongue), palatine(palate), buccal and labial(lips) glands.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-70632199058540401942013-09-02T03:29:00.000-07:002013-09-14T13:00:01.592-07:00Muscles of the head <div class="separator" style="clear: both; text-align: center;">
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There are two groups of muscles. They are craniofacial and masticatory muscles. The craniofacial muscles are related to eye orbital margins, eyelids, nose, nostrils, lips, cheeks, mouth, pinna, and the scalp. These musclesare also known as muscles of facial expression. Among these muscles those that are related to the lip movement are significant. The facial expression is mostly due to lip movement and positioning of the lips. Such thought related movements are caused by several muscles associated with lips and the skin around the mouth. Since orbicularis oris and buccinator muscles provide lip movement for kissing posture they are known as “kissing muscles”. Smiling is accomplished by zygomasticus major and minor, levator anguli oris and risorius. The muscles of the lips can also provide expressions such as sneering and frowning. The chin dimples are located between the mentalis muscles The masticatory (or speech) muscles move the mandible of the lower jaw. The muscles responsible for this movement are masseter temporalis and pterygoid. Tongue movements are caused by intrinsic and extrinsic muscles. Swallowing of food is facilitated by several muscles related to the mouth, roof of pharynx, uvula and other regions. II. Muscles of the Neck region. The movements of the neck region are caused by cervical, suprahyoid, infrahyoid and vertebral muscles.<br />
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<b>Muscles Of The Trunk Region :</b><br />
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The muscles of the vertebral column help to bend and rotate the body.These are strong back muscles that help the trunk to maintain erect posture. The most prominent muscles of this region are the erector spinae, longissimus and spinalis.Four important thoracic muscle groups are associated with the process of breathing. While the process of inspiration is due to scalene and external intercostal muscles, the expiration is performed due to internalintercostals and transverse thoracis. Major breathing movement is due to diaphragm, a curved musculofibrous sheet that separates thoracic and abdominal cavities. Abdominal muscles can aid in forced expiration, vomitting, defaecation, urination and childbirth. The inferior opening of the pelvic bone is covered by pelvic diaphragm muscles. Below these muscles perineum is pressent. The perineum and other “subfloor” muscles form the urogenital diaphragm. Pelvic andurogenital diaphragm may get strecthed in pregnancy due to weight of the foetus. However by specific exercises they can be strengthened.<br />
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<b>Muscles of the upper limb :</b><br />
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The hands are attached to the pectoral girdle and to the vertebral column by large conspicuous muscles such as trapezius, rhomboid major and minor, levator scapulae and lattissimus dorsi. The trapezius is a flat, triangular muscle. It extends over the back of the neck and upper thorax. It maintains the level and poise of the shoulder. It helps to rotate the scapula forward, so that the arm can be raised above the head. It helps to bend the neck backwards and laterally. Latissimus dorsi is a lar e flat triangular muscle. It is a conspicuous muscle stretching over the lumbar region and lower thorax. This muscle isuseful in adduction, extension and medial rotation of the humerus. It helps in the backward swinging of the arm. By raising the arm above the head it helps to pull the trunk upwards and forwards. It is useful in violent expiratory activities such as coughing or sneezing. It helps in deep inspiration. Serratus anterior and pectoralis major connect the ribs to the scapula. Pectoralis major extends from the upper thorax and abdomen to act on the humerus. It is a fan shaped muscle. It spreads between the clavicle and the 7th costal cartilage in the front of the chest. It helps to swing the extended arm forward and medially. It helps in climbing. It is active in deep inspiration.The muscles of the upper arm are the coracobrachialis, biceps,triceps and brachialis. The coracobrachialis arises from the coracoid bone in the shoulder and ends in the humerus of the upper arm. It helps to move the arm forward and medially. The biceps brachii is a large fusiform muscle. Ithas two proximal heads for attachement. They are connected to the coracoid and shoulder joint. The lower head ends in the radius of the lower arm. It is apowerful muscle causing flexing of the hand. The triceps arises by three heads from scapula and upper part of humerus on the posterior side. Thewrist, hand and finger movements are caused by several extrinsic and intrinsic hand muscles. A detailed study of them could be made in higher classes. V. M scles of the lower limb.Thigh movements are caused by anterior, postereolateral and deep muscles. The anterior muscles are the iliacus and psoas major which help to flex the thigh. The gluteus maximus form the mass of the buttocks region.Leg movement is caused by the anterior thigh muscles, quadriceps femoris and sartorius. The sartorius is the longest muscle of the body. It runs from the hip to the knee. Muscle movement of ankle foot and toe are caused by several groups of extrinsic and intrinsic muscles. A detailed study of them could be made in higher classes.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-67613247390562877872013-08-29T01:12:00.002-07:002013-08-29T01:12:51.448-07:00Muscular System <div class="separator" style="clear: both; text-align: center;">
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Locomotion and bodily movements are characteristic features of the animals. The movements are effected by various cell organelles such as cilia,flagella and organs like muscles. Muscular movements are more powerful and energetic. The skeletal muscles apart from their role in smarter movements, provide beautiful shapes to the body. The inner smooth muscles of the visceral organs make them work like machines all through the life period. The muscle cells function like small motors to produce the forces responsible for the movement of the arms, legs, heart and other part of the body. Thus the highly specialized muscle tissues are responsible for the mechanical processes in the body. Based on structure, functioning and occurrence three different types of muscle tissues have been identified. They are the skeletal, visceral and cardiac muscles.<br />
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1). <b>Skeletal muscles or striped muscles : </b>These muscles are attached to the bones. The muscle cells are long and cylindrical. These voluntary muscles cause body movements.<br />
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2). <b>Visceral muscles or Nonstriated muscles:</b> These are found in the walls of the inner organs such as blood vessels, stomach and intestine. The muscle cells are spindle shaped. These are involuntary in nature.<br />
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3). <b>Cardiac muscle</b> : These are found in the wall of the heart. The muscle cells are cylindrical and branched. The muscles are involuntary in nature. Skeletal muscles. he skeletal muscles are attached to bones by tendons. The tendons help to transfer the forces developed by skeletal muscles to the bones. These muscles are covered by sheets of connective tissue called fascia. Tendons : These are connective tissue structures showing slight elasticity. They are like cords or straps strongly attached to bones. The tensile strength of tendons is nearly half that of steel. A tendon having 10 mm diameter can support 600 - 1000 kg.<br />
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Fascia : These are assemblages of connective tissues lining skeletal muscles as membranous sheets. The fascia may be superficial or deep. The superficial fascia is a layer of loose connective tissue found in between skin and muscles. The deep fascia are collagen fibres found as a tough inelastic sheath around<br />
the musculature. They run between groups of muscles and connect with the bones.<br />
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<b>Shapes of muscles:</b><br />
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There is a wide variety of shapes and sizes in muscles. Based on general shape and the orientation or muscle fibres in relation to the direction of pull, they can be grouped into two classes.<br />
1. Parallel : These muscle fibres are parallel to the line of pull. The muscles may be flat, short, quadrilateral or long and strap like. The individual fibres run the entire length of the muscle.<br />
2. Oblique : These muscle fibres are oblique to the line of pull. The muscles may be triangular or pennate (feather-like). The pennate forms may be unipennate, bipennate, multipennate or circumpennate. Some muscles have a spiral or twisted arrangement. Naming of muscles. The muscles are named according to their size, shape, position and action.<br />
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<b>Naming of muscles :</b><br />
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<b>Shape</b> <b>Size</b><br />
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deltoid - triangular major - large<br />
quadratus - square minor - small<br />
gracilis - slender longus - long<br />
lattismus - broadest<br />
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<b>Number of Heads Position</b><br />
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biceps - 2 heads dorsi - of the back<br />
triceps - 3 heads pectoralis - of the chest<br />
quandriceps - 4 heads brachii - of the arm<br />
anterior, posterior.<br />
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<b>Depth Action</b><br />
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superficialis - superficial extensor<br />
internus - internal, flexor constrictor<br />
profundus - deep Flexor<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-65385721251421400082013-08-23T10:06:00.004-07:002013-08-25T04:01:44.033-07:00Skeletal System <div class="separator" style="clear: both; text-align: center;">
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The skeletal system is constituted by bones, cartilages and ligaments. This system provides ‘the shape’ to the body. Further, bones remain as regions for the attachment of muscles. It also helps to hold weight. Structureslike skull, protect inner organs. This system is also useful in locomotion. The bones remain as reservoirs of fat and certain minerals. The bone marrow is the site for the production of erythrocytes.<br />
The bones can be long, short, flat or irregular in shape. Hands and legs have long bones. Short bones are broad in shape. Carpals (wrist bones) and tarsals (antkle bones) are shorter. Flat bones are thin and flattened. Skullbones, ribs, sternum and scapula (shoulder blade) are flat bones. Verterbral and facial bones are irregular in shape. Structure of a typical long bone bone is covered by a double layered sheath called the periosteum.<br />
The outer layer of the periosteum is fibrous in nature. It is a dense collagenous layer having blood vessels and nerves. A growing long bone has three regions. The long bony part is the diaphysis or shaft. It is made up of compact bone. The end of the bone consists of epiphysis. It is made up of spongy bone. The outer surface of epiphysis is formed of compact bone. In between the epiphysis and diaphysis epiphyseal or growth plate is found. It is made up of hyaline cartilage. Growth in length of bone occurs at this plate. The cavity inside the diaphysis is called the medullary cavity. Thiscavity is lined by a membrane called the endosteum. The cavity inside the diaphysis in adults contain yellow marrow. It is mostly adipose tissue. The<br />
medullary cavity of the epiphysis contains red marrow concerned with blood cell formation.<br />
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Dried, prepared bones are used to study skeletal anatomy. The bones are named according to their position in the body. The named bones are divided into two categories: (1) the axial skeleton and (2) the appendicular skeleton. The axial skeleton consists of the skull, hyoid bone, vertebral column and thoracic cage. The appendicular skeleton consists of the limbs and<br />
their girdles. In human body, there are 206 bones, of these 80 are in the axial skeleton, 126 in the appendicular skeleton. Among the bones of the axial skeleton 28 bones are in the skull, 26 bones in the vertebral column, 25bones in the thoracic cage and one remains as the hyoid bone. (details as found below)<br />
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<span style="font-size: large;">Axial skeleton :</span><br />
It forms the upright axis of the body. It protects the brain, the spinal cord and the vital organs found within the thorax. a Skull - The human cranial capacity is about 1500 cm3 . It consists of 22 bones. It protects the brain. It supports the organs of vision, hearing, smell and taste. The lower jaw or mandible remains specially attached to the skull.<br />
The skull or cranium is covered by eight bones. They are one pair each of parietal and temporal, individual bones as frontal,sphenoid, occipital and ethmoid. These bones are joined by sutures to form a compact box like structure. The sutures are immovable join<br />
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<span style="font-size: large;">Skull - Lateral view :</span><br />
In the front there are 14 facial bones. Of these maxilla, zygomatic,palatine, lacrymal, nasal and inferior nasal koncha remain as pairs. Mandible or lower jaw and vomer are unpaired bones .The parietal and occipital bones are major bones on the posteriorside of the skull. The parietal bones are joined to the occipital bone at the back. The side of the head is formed of the parietal and the temporal bones.The large hole in the temporal bone is the external auditory meatus. Thisopening is meant for transmitting sound waves towards the eardrum. On thelateral side immediately anterior to the temporal, the sphenoid bone is seen. Anterior to the sphenoid bone is the zygomatic bone or cheek bone. It is a prominent bone on the face. The upper jaw is formed of the maxilla. Themandible constitutes the lower jaw.The major bones seen from the frontal view are the frontal bone, zygomatic bone the maxillae and the mandible. The most prominent openings in the skull are the orbits and the nasal cavity. The two orbits are meantfor accommodating the eyes. The bones of the orbits provide protection for the eyes and attachment points for the muscles that move the eyes. The bones forming the oribits are the frontal, sphenoid, zygomatic, maxilla, lacrymal, ethmoid and palatine. The head region also contains 6 ear ossicles. They are Maleus (2), incus (2) and stapes (2).<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-31821533220829100062013-08-23T09:46:00.004-07:002013-08-23T09:46:37.797-07:00Human Anatomy <span style="font-size: large;">History Of Human Anatomy :</span><br />
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The term ‘anatomy’ is Greek in origin. It takes its root from ‘ana’ and ‘tome’ (ana-up ; tome-cutting). Thus anatomy is the science of physical structure of an animal or plant studied by dissection. The Human Anatomy provided the necessary knowledge for surgery and medicine. The study of human anatomy dates back to 2500 BC, when the Egyptians prepared mummies. They removed internal organs of cadavers being mummified. They also did surgery for wounds and broken bones. In India during 500 - 491 BC Susruta performed cataract operation. In 1st century AD, Celsus, a Roman physician wrote about surgical procedures. The year 1543 AD was significant due to publication of an accurate book on Anatomy by Andreas Vesalius. In 1628 William Harvey described the functioning of heart and the movement of blood in animals. These earlier works were followed by the discovery and accurate account of each and every organ system and organs in human body. In the recent times, attempts are being made to understand the molecular arch tecture in every cell of our body. The Integumentary SystemThe word integument means covering. The integumentary system covers the outside of the body. It protects internal structures, prevents the entry of infectious agents, reduces water loss, regulates body temperature, produces vitamin D and detects stimuli such as touch, pain and temperature. Since the integument performs several functions, it is commonly referred to as Jack of all trades.</div>
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The skin or integument rests on layers of cells called hypodermis. The hypodermis attaches the skin to underlying bones and muscles. It supplies blood vessels and nerves to the skin. The skin is composed of two major tissues, namely dermis and epidermis. The dermis is mostly formed of connective tissue having fibroblasts, adipose cells and macrophages. It provides the structural strength tothe skin. The dermis accommodates nerve endings, hair follicles, smooth muscles and glands.</div>
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It is divided into two layers, namely the superficial papillary layer and deeper reticular layer. The papillary layer has projections called papillae. The reticular layer is the major layer of the dermis. It is dense in nature. It is continuous with the hypodermis.</div>
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<span style="font-size: large;">Epidermis:</span></div>
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The epidermis is made up of stratified squamous epithelium. It is separated from the dermis by a basement membrane. It contains meanocytes giving colour to the skin. Many of the cells of the epidermis produce</div>
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a protein substance called keratin. Hence they are called as keratinocytes. The deepest layers of the epidermis produce nerve cells by mitosis. As new cells are formed, the older cells are pushed to the surface. The surface cells will protect the inner new cells. Gradually the shape and chemicalnature of the surface cells will get altered. Slowly they get filled with keratin. This process is called keratinization. During this process the epidermis gets divided into five distinct regions or strata. They are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and stratum corneum.</div>
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Stratum basale is in the deeper region of the epidermis. It consists of one layer of columnar cells. Keratinization of cells begins in this region. Above this layer stratum spinosum is seen. It has 8-10 layers of polygonal cells. The stratum granulosum is the next upper layer. It has 3-5 layers of flattened cells. Above this layer stratum lucidum occurs. It is a thin zone having several layers of dead cells. The top most layer is called the stratum corneum. It consists of more than 20 layers of dead cells. These cells get filled with keratin. They are said to be cornified. The cornified cells are surrounded by a hard protective envelope. The skin can be either thick or thin. All five epithelial layers are seen in the thick skin. However stratum corneum contains more number of cells.</div>
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Thick skin is formed in the soles of the feet, the palms of hands and tips of fingers. The general body surface has thin skin. In the thin skin each epithelial layer inturn has few layers of cells. There are only one or two layers of cells in stratum granulosum.</div>
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<span style="font-size: large;">Callus :</span></div>
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The regions of skin subjected to constant friction or pressure are thickened to form the callus. The callus has several layers of cells in the stratum corneum.</div>
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<span style="font-size: large;">Skin colour :</span></div>
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The colour of the skin is due to pigments in the skin. The thickness of the stratum corneum and blood circulation can also cause skin colour. Normally the colour is caused by the pigment melanin. It provides colour to skin, hair and eye. It protects the body from sun’s ultraviolet rays. Melanin is produced by melanocytes. Melanin production is genetically determined. However, hormones and exposure to light can also alter the colour.</div>
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<span style="font-size: large;">Skin Dervatives :</span></div>
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<span style="font-size: large;">Hair :</span></div>
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The hairs are integumentary structures. A hair has a root and a shaft. While the shaft projects above the skin, the root remains well below the surface. The base of the root has a hair bulb. It is an expanded region. The shaftand most of the root of the hair are formed of dead keratinized epithelial cells. These are arranged in three concentric layers called the medulla, the cortex and the cuticle. The central axis of the hair is formed of the medulla. Major part of the hair is formed of a single layer of cells. According to the amount and types of melanin, the hair colour may vary. The colour of the hair is genetically determined. During old age the amount of melanin decreases causing white hair. Grey hair has a mixture of faded, unfaded and white hairs.</div>
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The hair growth is due to addition of cells at the base of the hair root. The growth stops at specific stages. After a resting period, new hair replaces old hair. The hairs on the head grow for a period of three years and rest for 1-2 years. </div>
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The muscle cells found associated with hair follicles are called the arrector pili. Contraction of these muscles cause ‘goose flesh’ making the hairs to ‘stand on end’.The skin has sebaceous glands and the sweat glands. The sebaceous glands are located in the dermis. They produce an oily substance called the sebum. These glands are connected by a duct to the upper part of the hair follicles. The mammary glands are the modified sweat glands.</div>
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The most common type of sweat gland on the skin are the merocrine glands. They are simple coiled tubular glands. They open directly on to the skin through sweat pores. The gland has two parts. They are the deep coiled portion and the duct which passes to the surface of the skin. The number ofsweat glands are more in the palms of the hands and soles of the feet.</div>
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<span style="font-size: large;">Nails :</span></div>
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Each nail is made up of two parts. They are the nail root and the nail body. The nail body is the visible part. The nail root is covered by the skin. The proximal and lateral edges of the nail are covered by nail fold.The stratum corneum of the nail fold grows onto the nail body as the eponchium. The free edge of the nail body is the hyponchium. The nail is found placed on the nail matrix and nail bed. A small white region seen at the base of the nail is the lunula. It contains the nail matrix. The nails grow at an average rate of 0.5-1.2 mm per day.</div>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-54384021328675998562013-08-23T09:43:00.004-07:002013-08-23T09:43:40.770-07:00Causes for Cancer (Etiology):<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuppsAX7GI2wyerahxYuuI02sIhuhyS7Wu5CqmCOPLSALrei-WaSrzoIOyEpJ0SEQw_Nv3daBLaKVKSbqa3Gl3Hq9KWuOQzVtZjiUIjzS8f__F02WZd1o7pHzcQnay8GBIyCkzzPVA0d4/s1600/cancer-lambert_2469736b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuppsAX7GI2wyerahxYuuI02sIhuhyS7Wu5CqmCOPLSALrei-WaSrzoIOyEpJ0SEQw_Nv3daBLaKVKSbqa3Gl3Hq9KWuOQzVtZjiUIjzS8f__F02WZd1o7pHzcQnay8GBIyCkzzPVA0d4/s400/cancer-lambert_2469736b.jpg" width="400" /></a></div>
<br />
Majority of the cancers are caused by living habits and environmental factors.<br />
<br />
1. Tobacco :- Nearly 35% of all cancer deaths are due to usage of tobacco in some form. Atleast 90% of lung cancer deaths are due to smoking. Smoking can also affect gastro-intestinal tract, pancreas, genito-urinary tract and upper respiratory passage. Snuff and chewing tobacco can affect mouth and respiratory tracts. Smoke inhaled by non-smokers (passive smoke) can also cause lung cancer and blood cancer.<br />
2. Exposure to ionising radiations such as x-rays, gamma rays, uv rays can produce cancer. These radiations rupture DNA strands, causing mutations.Solar radiations can cause skin cancers.<br />
3. Physical irritants, such as continued abrasion of the linings of the intestinal tract by some types of food can also lead to cancer. Dietary substances such as fat, high calorie intake of animal proteins, salted or smoked food can cause cancer in Breast, Colon, Stomach and Oesophagus.<br />
4. Certain drugs if taken without medical advice can cause cancer.<br />
5. Viruses and parasitic organisms like schistosoma, liverfluke can also affect.<br />
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<span style="font-size: large;">Cancer And Death :</span><br />
<br />
A severe onset of cancer ends in the death of a person. It is because of the unique characteristics of the cancer cells. The growth of normal cells is controlled by certain factors. However the cancer cells do not require the growth factors. Hence these cells do not respect usual cellular growth limits.Normal cells have a nature of remaining together in tissues. But the cancer cells are less adhesive to each other. Hence they wander through the tissues and enter the blood. They can be transported to all parts of the bodyand cause new cancer growths.<br />
The cancer cells rapidly multiply. Some cancers also produce angiogenic factors that cause many new blood vessels to grow into the cancer.<br />
Thus these cells will drain all the nutrients and normal cells get deprived of food. Ultimately the normal cells and tissues suffer nutritive death.<br />
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<span style="font-size: large;">Management Of Cancer :</span><br />
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The treatment or management of cancer depends on an accurate diagnosis. Diagnosis is made through microscopic observations(tissue biopsy), study of markers on the surface of cells, cytochemical methods, cytogenetics and various scanning and ‘x’ ray diagnostic methods. In order to compare results and for communicating treatment<br />
programme among medical personnel staging systems are essential (Ex: stage1, stage2) staging defines tumours as either confined to the tissue of origin or having spread to local tissues and organs and finally as having metastasized. After diagnosis, treatment of cancer involves surgery, chemotherapy, radiotherapy and hormonal treatments. Till last century, surgery was the only effective method of treatment. Even to-day through surgery biopsy can be effected for diagnosis. If the tumour is restricted to the primary site, through surgery it can be removed. In latest treatment procedures surgery is restricted to affected region, rather than amputation or removal of the entire organ.<br />
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<span style="font-size: large;">Radiotherapy :</span><br />
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Discovery of x-rays by Roentgen(1895) and of radioactivity by Curies in 1899 opened new ways of treating cancer. In Radiotherapy high energy ionising radiations are used. The radiations used are x-rays and gamma rays or subatomic particles such as beta particles, high energy electrons and neutrons or charged particles like helium ions. Ionising radiations can penetrate tissues. They can damage DNA leading to cell death and mutagenesis. The basis of radiation therapy depends on the differential sensitivity of the tumour tissue and the normal tissue. Hence the aim of radiotherapy is to prescribe sufficient radiation dose to the tumour, sparing as much of the normal tissue as possible.<br />
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<span style="font-size: large;">Chemotherapy : </span><br />
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The purpose of chemotherapy is to prevent cancer cells from multiplying, invading and metastasizing. The chemicals used in treatment affect cell multiplication and tumour growth. Several drugs are now available for usage. They can used singly or in combination. Some cancers like breast cancer are hormone dependent. Hence hormones are used in their management. Inspite of all advances in diagnostics and treatment, the death rate due to cancer is greater. Primary prevention of cancer will be a better alternative to diagnosis and treatment. 70% to 80% of cancers result from environmental causes. Hence public awareness towards environmental issues is a need. 33% of cancers in India are tobacco related. Hence smoking cessation and other measures to reduce tobacco usage are to be insisted upon. Consumption of fibrous food and avoidance of fatty food will avoid tumours related to alimentary canal. Thus it is apparent that fight against cancer will be successful with early detection and appropriate education for avoidance.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-54630381618666022152013-08-23T09:39:00.000-07:002013-08-23T09:39:00.875-07:00 Cancer <div class="separator" style="clear: both; text-align: center;">
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Cancer is a proliferation of cells which grow in an uncontrolled manner, invading local tissues and spreading widely through the blood or lymphatics to produce secondary deposits, or metastases in distant parts of the body.<br />
The word ‘cancer’ comes from Latin, meaning a crab. A tumour was called a cancer because of swollen veins around the area resembling a crab’s limbs. The study of cancer is called Oncology. Oncology is a word derived from the Greek, onchos, a lump, or tumour. The abnormal tissue growth is called neoplasm. If a neoplasm can cause harm by spreading, it is said to be malignant.<br />
Cancer was known to ancient civilizations. However the disease as it would be defined today was established as an entity by German pathologistsof 19th century. They described cellular nature of cancer and classified cancer. At the beginning of the 20th century, most major forms of cancer had been described. Further, attention was focused on finding the cause and introducing treatment. In 1775 Pott recognised cancer in chimney sweeps. He associated soot with cancer. From this time onwards environmental and occupational hazards were recognised as follows :<br />
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shale oil<span class="Apple-tab-span" style="white-space: pre;"> </span> skin cancer in workers<br />
radio active ores<span class="Apple-tab-span" style="white-space: pre;"> </span>lung cancer in miners<br />
beta-naphthylamine <span class="Apple-tab-span" style="white-space: pre;"> </span>bladder cancer in rubber industry workers<br />
cigarettes <span class="Apple-tab-span" style="white-space: pre;"> </span> <span class="Apple-tab-span" style="white-space: pre;"> </span>lung cancer<br />
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Later it was discovered that certain viruses can also cause cancer.One of the earliest virus, causing cancer, described was Rous sarcoma virus. Recently, human T-cell leukaemia has been found to be due to the virus HTLV-1.<br />
Some forms of cancer can also be inherited. A rare eye tumour, retinoblastoma is inherited. It is a dominant character showing Mendelian inheritance.<br />
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<span style="font-size: large;">Cancer In Biology :</span><br />
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The knowledge of cancer biology is growing rapidly. Researches are being conducted to fully understand the development of cancer at the cellular or molecular level. The available information is not sufficient for satisfactory<br />
treatment of cancer. During normal development and growth the cells in our body divide mitotically and get differentiated to specialized cells of the tissues. The processes of cell mitosis, growth and differentiation are controlled by cellular<br />
genes. Cancer is caused due to mutation or abnormal activation of such genes. such a mutation can happen in a single cell. Thus it may be monoclonal in origin. With further growth of cancer, additional mutations may occur in the daughter cells giving rise to subclones. The mutated cells may remain as heterogeneous cancer cells. Among these subclones some may have greater capacity and metastasize to distant tissues. They may also remain more resistant to damage from various anticancer treatments. The cancer cells have characteristic properties. They can be differentiated from normal cells under microscopic observation. These cells have<br />
large nuclei. In each cancer cell, the ratio of nucleus to cytoplasm is high. They have prominent nucleoli. The cells can grow indefinitely in culture medium. As component cell of a tissue they remain less differentiated. Even after getting organised into tissues unlike other cells they do not lose their replicative capacity. Cancer cells have the ability to invade surrounding<br />
tissues. The sequence of events that convert a normal cell into a cancer cell is called carcinogenesis. The process of carcinogenesis includes, intiation, growth, promotion, conversion, propagation and progression. Progression<br />
includes the processes of invasion and metastasis. Mature cancers have relatively uncontrolled growth, behaviour. As other normal cells they do not show any of the normal intracellular and extracellular growth control mechanisms. Initially the cancer cells have an<br />
exponential growth. Gradually their growth surpasses blood vascular supply. This results in slowing down of growth.<br />
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<span style="font-size: large;">Molecular Biology of Cancer :</span><br />
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Techniques in molecular biology have helped in understanding the most intimate structure of the cancer cell. It has been found that at molecular level two mechanisms operate.<br />
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1. The parts of genome involved in cell growth become activated. These are called the ‘proto-oncogenes’. These strands of DNA induce malignant growthtranformation in the cells. The conversion of proto-oncogenes into oncogenes can happen due to ‘point mutations’ on DNA. Further such cancer cells dis play chromosomal abnormalites such as duplication, deletions and translocations. Thus such alterations in gene arrangement can lead to generation of oncogenes. Oncogenes of human tumours gr hox11 Acute T-cell leukemia Translocation erbB-2 Breast and ovarian carcinomas Amplification L-myc Lung carcinoma Amplification ret Thyroid carcinoma DNA rearrangement. A distinct mechanism by which oncogenes are activated in human tumors is amplification. It results in elevated gene expression. Gene amplification is very common in cancer cells. It occurs a thousand times more frequently than in normal cells. Molecular biologists are now working on the products of oncogenes.<br />
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2. The growth of normal cells is controlled by suppressor genes. In cancer, parts of the genome functioning as the suppressor gene are either lost or inactivated. Hence, negative regulators of cell proliferation are removed. It contributes to the abnormal proliferation of cells.<br />
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<br />
Gene Type of cancer<br />
<br />
APC Colon / rectum carcinoma<br />
BRCA 1 Breast and ovarian carcinoma<br />
1 NK 4 Melanoma, lung carcinoma, brain tumors, leukemias, lymphoma<br />
Rb Retinoblastoma<br />
PTEN Brain tumors, kidney and lung carcinomas.<br />
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The protein products of the tumor suppressor genes normally inhibit cell proliferation. Inactivation of such genes therefore leads to tumor development. The complete sequence of events required for the development of any human cancer is not yet known. But it is clear that both the activation of oncogenes and the inactivation of tumor suppressor genes are critical steps in tumor initiation and progression. Simultaneous effect on both the genes will result in multiple genetic defect. It results in the increased proliferation, invasiveness and metastatic potential of cancer cells.<br />
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<span style="font-size: large;">Types of cancer:</span><br />
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Cancers are named according to the tissues from which they arise.<br />
1. Sarcoma - Malignancy in structural tissues Ex: Osteosarcoma (bones), liposarcoma (fa).<br />
2. Carcinoma - Epithelial cancers. Ex : Lung carcinoma, breast carcinioma.<br />
3. Lymphoma - Lymphatic tissues<br />
4. Leukemia - White blood cells.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-81775338680497688212013-08-23T09:21:00.000-07:002013-08-23T09:21:41.668-07:00Lysosomes<div class="separator" style="clear: both; text-align: center;">
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Lysosomes :<br />
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These are tiny vesicles surrounded by a membrane. Lysosomes are involved in intracellular digestion and are primarily meant for destroying unwanted and aged organelles inside the cells. Lysosomes were initially named as ‘perinuclear dense bodies’. Thename ‘lysosome’ was coined by C.de Duve in 1955. Lysosomes occur in all animal cells. However they are not found inmature mammalian erythrocytes. Muscle cells contain very few lysosomes.They are numerous in epithelial cells of secretory and excretory organs. Each lysosome is a round structure. It is filled with a dense material.Their shapes and densities vary. Their size ranges from 0.2 to 5 µm. Recent studies reveal that lysosomes may contain upto 40 types ofhydrolytic enzymes. The enzymes are mostly proteases, nucleases, glycosidases, lipases, phospholipases, phosphatases and sulphatases. Lysosomes originate either from the Golgi apparatus or directly from the endoplasmic reticulum. The enzymes they contain are used in the dissolution and digestion of redundant structures or damaged macromolecules from within or outside the cell. For example, when an animal cell ingests food into a food vacuole, lysomes fuse with the vacuole and break down the contents. Their enzymes digest carbohydrates, fat and proteins. The glands in some digestive organs package their digestive enzymes in lysosomes before releasing them outside the membrane. When a cell dies its own lysosomes release the enzymes that digest the remains of the cell in a process known as autolysis.<br />
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Peroxisomes :<br />
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These are spherical organelles bounded by a single membrane. They are found in the cells of Protozoa, fungi, plants, liver and kidney of vertebrates. The name peroxisomes was coined by C.de Duve and P. Baudhuin (1966)Peroxisomes contain catalase, an enzyme that catalyses the decomposition of hydrogen peroxide to the harmless products, water and oxygen. Hydrogen peroxide is a by- product of certain reactions of metabolism. It is potentially a very harmful oxidising agent.<br />
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Centrioles :<br />
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The centrioles are two cylindrical, microtubular structures found near the nucleus. When a centriole supports a flagellum or cilium, it is called the basal body. The centrioles occur in most of the animal cells, algal cells and some fern cells. They are absent in prokaryotes, red algae, yeast cells and flowering plants and some non -flagellated or non-ciliated protozoans. The centrioles range in size from 0.15-0.25 µm in diameter. They are usually 0.3-0.7 µm in length. Each centriole and basal body is formed of nine triplet microtubules equally spaced around a perimeter. Each microtubule has a diameter of 200- 260 Å in diameter.The microtubules are made up of a structural protein, tubulin, along with lipid molecules. It was initially considered that new centrioles arise by the division of existing centrioles.This idea is no longer accepted. It appears that new centrioles are produced de novo or are synthesized using an existing centriole asa template. In most of the animal cells the centrioles are the focal point for the centrosome. The centrosome organizes cytoplasmic microtubules during interphase in mitosis. It provides the two poles of the mitotic spindle. The centrioles form the basal body and the cilia. In spermatozoon one centriole gives rise to the tail fibre or flagellum. The centrioles are also involved in ciliary and flagellar activity.<br />
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Nucleus :<br />
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The nucleus is the most important organelle of cell. It controls all metabolic processes and hereditary activities of the cell. The nucleus was first discovered and named by Robert Brown in 1833. The occurrence of a nuclear membrane was first revealed by O. Hertwig in 1893. The nucleus is found in all the eukaryotic cells of plants and animals.However some eukaryotic cells such as the sieve tubes of higher plants and mammalian erythrocytes have no nucleus. Usually the cells contain single nucleus (mononucleate). However certain cells may have more than one nuclei. Accordingly they may be called binucleate or polynucleate cells. The polynucleate cells of the animals are called syncytial cells (Osteoblast cells)The shape of the nucleus may be spherical, elliptical or discoidal. In certain cells the nucleus is irregular in shape.The size of the nucleus may vary from 3 µm to 25 µm in diameter. Thesize is directly propotional to that of the cytoplasm. Nuclear size may also be determined by the number of chromosomes or ploidy. The nucleus of the haploid cells are smaller than that of the diploid cells. The nucleus is surrounded by a nuclear envelope. This envelope is comprised of two membranes of 5-10 nm thickness. The inner nuclear membrane supports a fibrous sheath called the nuclear lamina.The innernuclear membrane is surrounded by the outer nuclear membrane. The space between the inner and outer membranes is known as perinuclear space. It is a 10 to 50 nm wide fluid filled compartment.The nuclear lamina is a protein meshwork. It is a very dynamic structure.<br />
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The nuclear envelope is perforated by nuclear pores. Each pore hasa diameter between 10 nm to 100 nm. It has been calculated that the nuclear pores account for 5 to 15 percent of the surface area of the nuclear membrane. There is continous movement of molecules across the nuclear envelope through the pores. The nucleus is filled with a transparent semisolid matrix known asnucleoplasm or nuclear sap. The chromatin threads and the nucleolus remain suspendended in the nucleoplasm. The nucleoplasm is composed of nucleoproteins, proteins, enzymes and minerals. The nucleoplasm contains several thread like coiled structures. Theseare the chromatin fibres. During the cell division they become thick ribbon like structures known as chromosomes. The chromatin is made up of Deoxy - ribose nucleic acid (DNA) and proteins.<br />
The nucleus contains one or more spherical colloidal structures called nucleoli. The size of nucleolus is related to the synthetic activity of the cell The number of nucleoli in the cells may be one, two or four. Chemically, nucleolus contains DNA of nucleolar origin, four types rRNA, 70 types of ribosomal proteins, RNA binding proteins and RNA splicting nucleoproteins. Ribosomal subunits are synthesized in the nucleolus. Initiation, production and maturation stages of ribosomal formation happen in three distinct regions of the nucleolus. Chromosomes<br />
The chromatin fibres get condensed into chromosomes during cell divisions. They are capable of self-reproduction and they play an important rloein heredity. The nucleus was first observed and described by karl Nagli (1842) in the nuclei of plant cells. Chromosomes and their role in cell division was first explained by A. Schneider (1873). In 1887 Benden and Bovery reported that the number of chromosomes for each species is constant. T. H Morgan and H. Muller in 1922 revealed the occurrence of nearly 2000 genetic factors on four chromosomes of Drosophila. In 1924, Robert Feulgen showedthat chromosomes contain DNA.<br />
The number of chromosomes is constant for a particular species.The reproductive cells such as sperm or ovum has one set of chromosomesand it is known as the haploid set(n). It is also known as the genome. The somatic or body cells contain two haploid set or genomes and are known as the diploid cells (2n). The diploid condition is arrived at by the union of the haploid male and female gametes in the sexual reproduction.<br />
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Number of Chromosomes<br />
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Common name Scientific name Chromosome Number<br />
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Paramoecium P. aurelia <span class="Apple-tab-span" style="white-space: pre;"> </span> 30-40<br />
Hydra H. vulgaris <span class="Apple-tab-span" style="white-space: pre;"> </span> 32<br />
Housefly Musca domestica <span class="Apple-tab-span" style="white-space: pre;"> </span> <span class="Apple-tab-span" style="white-space: pre;"> </span> 12<br />
Fruit fly Drosophila sps<span class="Apple-tab-span" style="white-space: pre;"> </span> 8<br />
Pigeon Columba livia 80<br />
Gorilla Gorilla gorilla 48<br />
Man Homo sapiens 46<br />
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The size of a chromosome can be measured during mitotic metaphase. It may range from 0.25 µm to 30 µm.<br />
The shape of the chromosome changes from phase to phase. Each chromosome has a clear zone, known as centromere or kinetocore along their length. The centromere divides the chromosome into two parts. Each part is called the chromosome arm. Thus according to the position of the centromere and nature of the chromosome arm, the chromosomes may be Telocentric, Acrocentric, Submetacentric and Metacentric.<br />
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-51574743222065348522013-08-23T04:44:00.000-07:002013-08-23T08:09:03.740-07:00Endoplasmic Reticulum <div class="separator" style="clear: both; text-align: center;">
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Electron microscopic study of sectioned cells has revealed the presence of a three dimensional network of sac-like and tubular cavities called cisternae bounded by a unit membrane inside the cell. Since these structuresare concentrated in the endoplasmic portion of the cytoplasm, the entire organisation is called the endoplasmic reticulum. This name was coined by Porter in 1953. The occurrence of ER varies from cell to cell. They are absent in erythrocytes, egg cells and embryonic cells. The ER is the site of specific enzyme controlled biochemical reactions. Its outer surface carries numerous ribosomes. The presence of ribosomes gives a granular appearance. In this condition ER is described as rough endoplasmic reticulum (RER). RER is the site of synthesis of proteins. Ribosomes are absent on smooth endoplasmic reticulum (SER). SER is concerned with lipid metabolism.<br />
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<span style="font-size: large;">Lamellar form or Cisternae :</span><br />
These are long, flat, sac like tubules. Their diameter is about 40-50 µm. The RER has a synthetic role. It is mostly seen in cells of pancreas, notochord and brain.<br />
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<span style="font-size: large;">Vesicles :</span><br />
These are oval, vacuolar structures. Their diameter is about 25-500 µm. They occur in most of the cells.<br />
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<span style="font-size: large;">Tubules :</span><br />
These are branched structures forming the reticular system along with the cisternae and vesicles. They have a diameter of 50-190 µm. They occur in almost all cells.<br />
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<span style="font-size: large;">Functions :</span><br />
1. It provides skeletal framework to the cell.<br />
2. It facilitates exchange of molecules by the process of osmosis, diffusion and active transport.<br />
3. Enzymes of ER control several metabolic activities.<br />
4. They serve as intracellular transporting system.<br />
5. It conducts intra-cellular impulses.<br />
6. It helps to form nuclear membrane after cell division.<br />
7. SER synthesises lipids.<br />
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<span style="font-size: large;">Golgi apparatus</span> :<br />
The Golgi apparatus was discoverd by an Italian neurologist, Camillo Golgi in 1873.The Golgi apparatus occurs in almost all animal cells except red blood cells. Animal cells usually have a single Golgi apparatus. Some cells have more of Golgi apparatus. In most of the ectodermal and endodermal cells it occurs in between the nucleus and the periphery. In nerve cells it occupies a circum-nuclear position.<br />
The simplest unit of the Golgi apparatus is the cisterna. A cisterna is about 1 µm in diameter. It has a membrane bound space. This space accumulates secretions. Numerous such cisternae are associated with each other and appear in a lamellar arrangement. In the lamellar arrangement the space between each cisterna is 20-30 nm. A group of these cisternae is called the dictyosome. A group of dictyosomes constitute the Golgi apparatus.Typically a Golgi apparatus appears as a complex arrangement of interconnecting tubules, vesicles and cisternae.<br />
The Golgi apparatus is the site of synthesis of biochemicals.They also collect proteins and lipids made in the ER and add additional substances.<br />
<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6851775650996342302.post-53915940516299508302013-08-23T04:34:00.000-07:002013-08-23T04:40:05.404-07:00Mitochondria:<div class="separator" style="clear: both; text-align: center;">
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The mitochondria are filamentous or granular cytoplasmic organelles of all aerobic cells of higher animals and plants. They are also found in micro organisms including Algae, Protozoa and Fungi. They were first observed by Kolliker in 1850 as granular structures in the striated muscles. The name ‘mitochondria’ was given to them by Benda (1897-98). Various steps of glycolysis in mitochondria was discovered by two German biochemists Embden and Meyerhof. Embden got the Nobel Prize in 1922. Sir Hans Adolph Krebs, in 1937 found out various reactions of citric acid cycle. Kennedy and Lehninger (1948-50) showed that Citric acid cycle, oxidative phosphorylation and fatty acid oxidation took place inthe mitochondria. The number of mitochondria in a cell depends on the type and functional state of the cell. Certain cells contain large number of mitochondriae.g., eggs of sea urchin contain 140,000-150,000 mitochondria. Oocytes of amphibians contain 300,000 mitochondria. Liver cells of rat contain only 500-1600 mitocho dria. Some algal cells may contain only one mitochondrion.The mitochondria may be filamentous or granular in shape. They vary in size from 0.5 µm to 2.0 µm. Due to their minute nature they can not be seen under light microscope. Each mitochondrion is bound by two highly specialized membranes.<br />
The outer membrane is smooth. It is separated from the inner membrane by a 6-8 nm wide space. The inner membrane is highly convoluted, forming a series of inflodings known as cristae.<br />
Thus mitochondria are double membrane envelopes. The inner membrane divides the mitochondrial space into two distinct chambers. The outer compartment is the peri-mitochondrial space. It is found between outer and inner membranes. The inner compartment is the matrix space. It is filled with a dense gel like substance called mitochondrial matrix. The matrix contains lipids, proteins and circular DNA molecules. The outer and inner membranes, intermembrane space and mitochondrial matrix contain several enzymes. Hence the mitochondria perform several important functions such as oxidation, dehydrogenation, oxidative phosphorylation and respiratory chain of the cell. Since mitochondaria play a key role in the oxidation of carbohydrates and fats, they are considered as the actual respiratory organs of the cells. During such biological oxidations large amount of energy is released. The energy is utilized by the mitochondria for synthesis of the energy rich compound known as adenosine tri phosphate or ATP. Due to this function, the mitochondria are also known as “power houses” of the cell. In animal cells mitochondria produce 95 % of ATP molecules.<br />
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<b><span style="color: #3d85c6; font-size: x-large;"><u>Ribosomes</u>:</span></b></h2>
The ribosomes are small dense, rounded and granular particles. They contain ribonucleoprotein. They occur either freely in the matrix of the mitochondria, chloroplast and cytoplasm or remain attached with the membrane of the endoplasmic reticulum and nucleus. The ribosomes were described by G.E.Palade in 1952. The name ‘ribosome’ was coined by R. B. Roberts in 1958. The ribosomes occur in both prokaryotic and eukaryotic cells. In the cells in which active protein synthesis takes place, the ribosomes remain attached with the membranes of the endoplasmic reticulum. The cells where such active synthesis happens are pancreatic cells, hepatic cells, osteoblasts, serous cells of submaxillary gland, chief cells of the glandular stomach, thyroid cells and mammary gland cells. The ribosomes are spheroid structures with a diameter of 150 to 250 Å. Each ribosome is composed of two subunits. One subunit is large in size and has a dome like shape. The other ribosomal subunit is smaller in size and it occurs above the larer subunit forming a cap-like structure. The ribosomes are chemically composed of RNA and proteins. The ribosomal RNA (rRNA) play a central role in the process of protein synthesis.The ribosomal proteins enhance the catalytic function of the rRNA. The functioning of rRNA is under genetic control.<br />
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