Objectives Enumerate of Basic Tissues Define and mention the Epithelium Define and discuss the Connective Tissues Define and discuss the Muscular Tissues Define and describe the Nervous Tissues Basic Tissues of Body 1.Epithelium 2.Connective Tissues 3.Muscular Tissues 4.Nervous Tissues EPITHELIUM Definition: Layered collection of closely packed cells with very little intercellular material, usually covering the external or internal surface of body. Epithelium Epithelial cells also modified to form the glands which may be exocrine glands or endocrine glands. Epithelium Epithelium is avascular, but supported by connective membrane, called as Basement Membrane, which made up of loose connective tissues with blood vessels. Simple cuboidal Epithelium Cuboidal Cell Basement Membrane EPITHELIUM Epithelium may covered the body surfaces like outer surface of body, the Skin or they line the luminal surface of hollow tubes or viscera, for e.g. blood vessels or Urinary Bladder. CLASSIFICATION Epithelium can be classified in three ways: I- Shape 1. Squamous 2. Cuboidal 3. Columnar 4. Transitional II- Stratification 1. Simple 2. Stratified 3. Pseudostratified III- Specializations 1. Keratinized 2. ciliated Classification Description Location Drawing /Function /Sketch Simple Thin single cell Artery, veins Squamous layer where the and width is greater for exchange than the cell’s Bowman’s height Capsule barrier Simple Thin single cell Kidney Cuboidal Layer where the absorption and width, depth, secretion Pancreas and height of absorption and the cell are conduit Approximately the same Classification Description Location Drawing /Function /Sketch Simple Thin single cell Gall Bladder Columnar Layer where the absorption height of the cell Small Intestine is much greater Absorption And than the width secretion Pseudostratified Stratified but Trachea Some cells do secretion/conduit not reach the Epididymis free surface but absorption/ All cells reach conduit The basement membrane Classification Description Location Drawing /Function /Sketch Stratified Multiple layers of Keratinized- squamous cells but the top Skin and layer is squamous Non- Keratinized – layer Keratinized- of dead apical cells Esophagus Non-keratinized – Act as layer of living apical barrier/ cells protection Stratified Multiple layers of Sweat cuboidal cells but the top glands, large layer is cuboidal ducts in Exocrine glands Classification Description Location Drawing /Function /Sketch Stratified Multiple layers Largest ducts of Columnar of cells but the exocrine glands, top layer anorectal is columnar junction Transitional Stratified Urinary (Urothelium) Epithelium has bladder the ability to barrier, change form Distensible Quickly to property increase surface area Definition Connective tissues are also called as supporting tissue, these type of tissues support and connect the other body tissues. Connective tissues of the cells, which are scanty, embedded into ground substance, the Matrix (ground Substance and fibers), containing cells and fibers Components of Connective Tissue The connective tissue consists of:- 1. Cells 2. Fibers 3. Ground Substance Matrix is the combination of fibers and ground Substance CONNECTIVE TISSUE CELLS Many cells are found in different varieties of connective tissues. Cells are found in connective tissue proper are: 1. Fibroblast 2. Fat Cells 3. Histiocytes 4. Plasma Cells 5. Mast Cells 6. Some white blood cells The cells which are present in the connective tissue all the time are called as fixed connective tissue cell, these are Fibroblast and Fat cells remaining cells are appear on demand they are called as Wandering Cells. Only loose areolar connective tissue contains all varieties of cells, other connective tissue varieties contain one or more tissue cells types. FIBROBLASTS Most abundant variety of connective tissue cells. Fibroblasts appear as large, flattened, roughly ovoid cells with processes. Functions: Produce various connective tissue fibers Secret the Ground Substance HISTIOCYTES (Macrophages) Abundantly found in loose areolar connective tissue, being most numerous as fibroblast. They are derived from Monocytes. In inactive phase histiocytes do not easily differ from fibroblast. In resting condition, histiocytes appear as irregular cells with short blunt process. Activated histiocytes become clearly distinguishable from fibroblast. HISTIOCYTES (Macrophages) Entire cell becomes larger with bigger, cytoplasm filled with granules and vacuoles containing ingested material. Function: Related to defense mechanism, act as scavenger cells, because of their mobility and engulf dead cells, extravasated red blood cells, bacteria and foreign bodies Plasma cells These cells are rare in connective tissue but mostly present at the sites where subject to penetration to bacteria and foreign proteins occur, like intestinal mucosa. They are frequently found in the lymphoid organs. Plasma cells are large and ovoid cells. The nucleus is spherical and eccentric in position. Plasma cells Within the nucleus, chromatin occurs as coarse granules arranged in a regular manner near the nuclear membrane, called as cart-wheel “appearance” Function: Production of antibodies MAST CELLS Mast cell is large, round or ovoid cell with centrally placed nucleus. The cytoplasm is full of coarse granules, presence of these nucleus gives these cells their name mast means well fed. MAST CELLS Mast cells are widely distributed in connective tissue but are more abundant in the loose connective tissue around the blood vessels. Functions: Secret Heparin, a powerful anticoagulant Histamine, potent Vasodilator FAT CELLS or ADIPOCYTES Fat cells are large, have an ovoid or spherical shape. The cytoplasm is displaced to the peripheral region of cell by a single large fat droplet. The nucleus, flattened and surrounded by a small amount of cytoplasm, is usually found pressed against the cell membrane. FAT CELLS or ADIPOCYTES In ordinary histological preparation, the fat is dissolved out of the cell and is represented by a large vacuole. Thus after staining the peripheral rim of cytoplasm and eccentric, flattened and nucleus collectively give a characteristic appearance “Signet Ring Appearance”. WANDERING CELLS Wandering cells are not normally present in the connective tissue but they are temporary shifted the blood and lymph. These include lymphocytes, eosinophils and neutrophils CONNECTIVE TISSUE FIBERS Connective tissue fibers are long, slender protein polymers . Connective Tissue fibers are three Major Varieties. Collagen Fibers Reticular Fibers Elastic Fibers These three types are found in different proportions in various types of connective. CONNECTIVE TISSUE FIBERS The predominate fiber type is responsible for the specific properties of connective tissue and specific tissue. For e.g. a connective tissue contains more collagenous fibers than this type is called as dense connective tissue, if a connective tissue contains abundant of Reticular fibers than this is called as loose connective tissue, if a connective tissue contains abundant of elastic fibers than it is called as Elastic connective tissue. CONNECTIVE TISSUE FIBERS Collagenous (white) fibers: are secreted by fibroblast. There are Bundles of Collagen Fibers different varieties of collagenous fibers, but most commonest Varieties are Type I & III (which is also called as Reticular Fibers) CONNECTIVE TISSUE FIBERS Reticular (thin) Fibers: are thin collagenous fibers of type III variety, they also secreted by the fibroblast. Both varieties usually take part in formation of Basement Membrane. CONNECTIVE TISSUE FIBERS Elastic (Yellow) Fibers: These fibers have elasticity, they Elastic Fibers can be stretched like rubber than come back to its original position. ELASTIC FIBERS Found in the connective tissues through out the body but they are particular abundant in the organs those are subject of constant pressure or pulling force and than return to their Elastic Fibers original size and shape for e.g. Lungs and large Arteries. Certain Ligaments are rich in elastic fibers and called as Yellow Elastic Ligament. Wall of Aorta GROUND SUBSTANCE The cells and fibers of connective issue are embedded in highly hydrated gel which is called as ground substance. The water contents in ground substance serves as the medium through which metabolites and gases are exchange between cells and blood vessels. GROUND SUBSTANCE Ground substance is an amorphous material contains Proteoglycans (rich in carbohydrates and less in Proteins) and Glycoproteins (less in Carbohydrates & rich in proteins). Mucopolysaccharide Ground Substance Ground substance Ground substance is found in all cavities and clefts between the fibers and cells of connective tissues. Water, salts and other low molecular substances are contained within the ground substance, but its main structural constituent are proteoglycans. Ground substance is soluble in most of the solvents used to prepare histological sections and therefore not visible in ordinary sections. Proteoglycans are responsible for the highly viscous character of the ground substance. Proteoglycans consist of proteins (~5%) and polysaccharide chains (~95%), which are covalently linked to each other. The polysaccharide chains belong to one of the five types of glycosaminoglycans, which form the bulk of the polysaccharides in the ground substance. Proteoglycans Different types of Proteoglycans are Glycosaminoglycan Hyaluronic acid s Non-sulfated Glycosaminoglycan chondroitin-4-sulfate, chondroitin-6- Sulfated sulfate, dermatan sulfate, heparan sulfate, heparin Glycoproteins fibronectin, laminin, Non Sulphated Glycosaminoglycans Properties Distributions Hyaluronic acid is the dominant Synovial fluid, glycosaminoglycan in connective umbilical cord, viterous tissues. Hyaluronic acid serves as humor, loose connective a "backbone" for the assembly of tissues other glycosaminoglycans in connective and skeletal tissue. Sulfated Glycosaminoglycan Chondroitin Cornea Chondroitin 4-sulfate Aorta, bone, cartilage, cornea Chondroitin Sulfate A Chondroitin 6-sulfate Cartilage, nucleus Pulposus, Chondroitin Sulfate C Sclera, tendon, umbilical cord Dermatan Sulfate Aorta, heart valve, Chondroitin Sulfate B ligamentum nuchae, sclera, skin, tendon Keratan sulfate Bone, cartilage, Cornea, nucleus pulposus, kidney glomerulus Sulfated Glycosaminoglycan Heparin Mast Cells Heparan Sulfate Lung, Arterial wall, cell surface Glycoproteins Fibrillar proteins Fibronectin: mediates adhesion between cells and extracellular matrix components Fibrillin: main component of microfibrils Elastin: hydrophobic protein which is the main component of elastic fibres Collagen: More than 19 different collagens have been identified Structural •Laminin: major component of basement glycoproteins membranes •Entactin: binds laminin to type iv collagen Basement Membrane The most important function of connective tissue is to support and nourish other tissue of body (Epithelia, Nervous and muscle tissues). The Basement Membrane is a thin layer of extracelluar material. The basement membrane is formed by the collagen fibers and proteoglycane. It supports the epithelia, muscles fibers and nerve fibers. Basement Membrane CLASSIFICATION OF CONNECTIVE TISSUE The connective tissues are classified into various types depending on the following Four Factors. 1. Relative proportion of the various fibers present 2. Compactness and arrangement of fibers 3. Nature of ground substance (matrix) 4. Types of cells On these ground the connective tissues are divided into basic Groups A. Embryonal Connective Tissue B. Adult Connective Tissues Connective Tissue Embryonal Adult Proper Cartilage Bone Mucous Mesenchyme Hyaline Fibro Elastic Regularly Arranged Dense Loose Irregularly Arranged Areolar Reticular Adipose Embryonal Connective Tissue Mesenchyme: developmentally, the connective tissue are derived from mesoderm which one of the three Primary embryonic Layers (others two are ectoderm and Endoderm). Immature connective tissue of embryo derived from the mesoderm is called as Mesenchyme. Embryonal Connective Tissue Mucous Tissue: At the later stages of development of foetus the mesnechmye acquired abundant of fibers, the increased number of fibers in mesenchyme now called as Mucous, which widely distributed through out the body of embryo. Mucous Tissue 1-LOOSE CONNECTIVE TISSUE Loose Areolar connective Tissue: This type is widely distributed through out the body. All three basic components of connective tissue (cells, fibers and ground substance) are best represented in the loose Green Lines - Collagen Fiber Blue Circle - Mast Cells aerolar connective tissue. Yellow arrows - Elastic Fiber 1- Loose Areolar connective Tissue: The two most common cell types, fibroblast and histiocytes are present but other varieties of cells also present. Collagenous fibers are more abundant but elastic fibers are also present. Reticular fiber are few in number. Distributions: Subcutaneous Tissue (Superficial & deep fascias) Mesentery Green Lines - Collagen Fiber Omentum Blue Circle - Mast Cells Yellow arrows - Elastic Fiber 2- RETICULAR CONNECTIVE TISSUE This variety of loose connective tissue consists of reticular cells and reticular fibers. Reticular cells have a stellate shape and possess long processes which pass indifferent directions to make contact with neighboring cells. Reticular Tissue 2- RETICULAR CONNECTIVE TISSUE Distributions: Forms the supporting network of the liver, spleen, bone marrow and lymphoid organs. Functions: Precursor for Fibroblast Producing Reticular fibers Phagocytic Properties 3- ADIPOSE TISSUE This variety of loose connective consists of entirely of fat cells, organized into lobules which are separated from each other by fibrous septa. Within a lobule, the individual fat cells are supported by a mesh work of delicate reticular fibers. 3- ADIPOSE TISSUE Distributions: Functions: Food reserve for the body Chief site for energy storage Mechanical functions for shock absorbing pad for e.g. sole of foot. Temperature Regulation By production heat as a result of metabolism of fat. By acting as the insulator under the skin & preventing the heat loss. DENSE CONNECTIVE TISSUE This variety of connective tissue proper is characterized by close packing of fibers. It contains fewer cells and lesser amount of amorphous ground substance but the number of fibers are more. DENSE CONNECTIVE TISSUE According to the arrangement of its component fibers, the dense connective tissue is subclassify into two categories: 1. Regularly Arranged connective Tissue 2. Irregularly Arranged connective Tissue REGULARLY ARRANGED CONNECTIVE TISSUE They are three types:- a- Tendons: composed of almost entirely of closely packed collagen fibers. A few fibroblasts are present b- Aponeuroses: have same structure as the tendon, but they are broad and thin. c- Ligaments: same as tendons but more sronger. IRREGULARLY ARRANGED CONNECTIVE TISSUE This type of dense connective tissue occurs in the form of sheets. It mainly consists of collagenous fibers, but elastic and reticular fibers are also present Distributions: Dermis of skin Capsules of some organs (liver, spleen, lymph nodes Fibrous Sheaths of cartilage (Perichondrium) Fibrous Sheaths of bone (periosteum) Composition of Blood Blood (about 5.5 L in a man) consists of the cells and fluid. Blood is made up of two parts: formed elements, or blood cells, and plasma, the liquid in which the formed elements are suspended. The formed elements are erythrocytes (red blood cells), platelets, and leukocytes (white blood cells). Composition of Plasma A typical sample of plasma is composed of 90% water, 8% protein, 1% inorganic salts, 0.5% lipids and 0.1% sugar, the rest being made of lesser components. The three main groups of protein in plasma are albumin, globulins & fibrinogen. Erythrocytes Erythrocytes contain large amounts of oxygen- carrying haemoglobin, are primarily involved in the transport of oxygen and carbon dioxide, and function exclusively within the vascular system. The whole mass of red blood cells and their precursors in the bone marrow is called the erythron. Leucocytes The leucocytes constitute an important part of the defence and immune systems of the body and, as such, act mainly outside blood vessels in the tissues; thus the leucocytes found in circulating blood are merely in transit between their various sites of activity. Types of Leucocytes Five types of leucocyte are normally present in the circulation. These are traditionally divided into two main groups based on their nuclear shape and cytoplasmic granules: Granulocytes Neutrophils Eosinophils Basophils Mononuclear leucocytes Lymphocytes Monocytes Platelets Platelets play a vital role in the control of bleeding (haemostasis) by plugging defects in Figure blood vessel walls and contributing to the activation of the blood- clotting cascade. Electron micrograph of human platelets. CONSTITUENTS OF BLOOD Blood is also a sub-variety of connective tissue. Blood consist of: • Formed Elements: Erythrocytes 3-5 million cells / cubic millimeter Leucocytes 4000 -1100 cells / cubic millimeter Platelets 150,000-400,000 cells / cubic millimeter • Plasma: the plasma is the liquid intercellular material that impart the fluid properties to the blood. The relative volume of the formed element and plasma is 45% and 55% respectively. PLASMA Although blood is a fluid but it may be taken as a connective tissue which consists of a ground substance, blood plasma, and cell elements, blood corpuscles. The only difference with the other connective tissues is that it does not contain fibers elements . The blood is slightly alkaline in nature (pH 7.4). Plasma is a yellowish, straw-coloured liquid which consists mainly of water (>90%). The other 10% of the blood plasma consists of dissolved substances of which the following are the most important: Organic constituents (2%) which include nutrients such as glucose, fats, amino acids and vitamins. PLASMA Inorganic salts and ions which include ions such as bicarbonates, phosphates, sulphates, chlorides, calcium potassium, sodium and magnesium. Secretions such as enzymes and hormones. Dissolved gases such as oxygen and carbon oxide, i.e. gases involved with respiration. Antibodies which are protective protein compounds. Plasma proteins (7%), the most important of which are fibrinogen, albumen and globulin. ERYTHROCYTES (RED BLOOD CORPUSCLES). In humans there are about 5 million erythrocytes per cubic millimetre of blood (3 to 5 million / cu mm) . Erythrocytes are small, round, bi- concave discs which float in the blood plasma. Each adult red blood cell represents a cell without a nucleus, which is surrounded by a thin, elastic membrane. They are soft, flexible and elastic and therefore move easily through the narrow blood capillaries. In living state each erythrocytes measures about 8 mm in diameter and 2 mm in maximum thickness. ERYTHROCYTES (RED BLOOD CORPUSCLES) Approximately 90% of the content of each erythrocyte is haemoglobin which supplies the characteristic colour of the red corpuscles. Red blood cells are formed in the red marrow of long and flat bones, especially in the spongy regions in the heads of the long bones. The life span of an erythrocyte is approximately 4 months. LEUCOCYTES (WHITE BLOOD CELLS) Leucocytes are far less numerous than red blood corpuscles. Leucocytes are larger than red blood corpuscles and have a definite nucleus. They are irregular in shape, slightly translucent and nearly colourless. They are able to change their shape because of the fact that they move by means of pseudopodia (false feet). Many are phagocytic, i.e. they are able to engulf micro-organisms and foreign intruders into their cytoplasm by flowing around them. There are five types of leucocytes which can be divided into two groups, namely granular white blood cells where the cytoplasm is granular, and non-granular white cells where the cytoplasm does not contain granules. VARIETIES OF LEUCOCYTES • Granular white blood cells Neutrophils 40-75% Eosinophils 1-6% Basophils 0.5-1% • Non-granular white cells Lymphocytes 20-40% Monocytes 2-10% NEUTROPHILS Neutrophils, are the most abundant type of white blood cells and form an integral part of the immune system. Their name arrives from staining characteristics on Hematoxylin and Eosin (H&E) histological preparations, cells stained as salmon pink (a shade of pink tinged with yellow ). These phagocytes are normally found in the blood stream. However, during the acute phase of inflammation, particularly as a result of bacterial infection, neutrophils leave the blood vessels and migrate toward the site of inflammation in a process called chemotaxis. NEUTROPHILS Neutrophils has polymorph nucleus that means nucleus has characteristic multilobulated shape. Neutrophils are the most abundant white blood cells; they account for 70% of all white blood cells. Function: Neutrophils are active phagocyte, capable of ingesting microorganisms or particles. EOSINOPHILS Eosinophil: A type of leukocyte with coarse round granules of uniform size within its cytoplasm and typically a bilobate (two-lobed) nucleus. Eosinophils are so named because their cytoplasmic granules stain red with the dye eosin. Eosinophils normally constitute 1 to 3% of the peripheral blood film. EOSINOPHILS Functions: Responsible for combating infection by parasites in the body. Play role in allergy and asthma. Locations: Thymus Gastrointestinal track, Ovary Uterus Spleen Lymph nodes. BASOPHILS Basophils are the least common of the granulocytes, representing about 0.0% to 0.3% of circulating leukocytes (white blood cells). They contain large cytoplasmic granules. The nucleus is visible and it usually has 2 lobes. The mast cell, a cell in tissues, has many similar characteristics. Like all circulating granulocytes, basophils can be recruited out of the blood into a tissue when needed. BASOPHILS Function Basophils play a role in acute allergic reactions. Their granules contain histamine and heparin, that are released in response to the presence of allergens. These substances cause increased vascular permeability, smooth muscle spasm, vasodilatation. LYMPHOCYTES • Lymphocytes are present in blood and also in the lymphoid tissues and organs too, as well as the lymph circulating in the lymphatic vessel. The lymphoid organs include thymus, bone marrow, spleen, lymphoid nodules, palatine tonsils, Peyer's patches and lymphoid tissue of respiratory and gastrointestinal tracts. • Most lymphocytes circulating in the blood is in a resting state. They look like little cells with a compact round nucleus which occupies nearly all the cellular volume. As a consequence, the cytoplasm is very reduced. In the blood, lymphocytes are 20-40 % of all leukocytes. LYMPHOCYTES The two major classes of lymphocytes are: B cells and T cells, which are processed in the thymus. Both B cells and T cells recognize specific antigen targets. B cells work chiefly by secreting soluble substances called antibodies into the body's fluids. (This is known as humoral immunity.) Antibodies typically interact with circulating antigens such as bacteria and toxic molecules. T cells, in contrast, interact directly with their targets, attacking body cells that have been commandeered by viruses or warped malignancy. (This is cellular immunity.) MONOCYTES Monocytes are the largest cells found in normal blood. The nucleus is centrally or peripherally located, indented, and ovoid or horseshoe- shaped; the nuclear chromatin is not as dense as that of lymphocytes. They consist of between 3 to 8 percent of the leukocytes in the blood. In the tissues monocytes mature into different types of macrophages at different anatomical locations. MONOCYTES A monocyte is a leukocyte, part of the human body's immune system that protects against blood- borne pathogens and moves quickly (aprox. 8-12 hours) to sites of infection in the tissues. Monocytes are usually identified in stained smears by their large bilobed nucleus. PLATELETS These are small, colourless, plate-like discs. No nucleus is visible. They are not true cells but are cytoplasmic fragments of large cells (megakaryocytis) found in red bone marrow. When tissue is damaged and the platelets leave the blood vessels, they release a substance which transforms soluble fibrinogen in the plasma to a network of fibrin threads. MUSCULAR TISSUE Consists of the muscular Tissue cells and intercellular substance. The cells of muscle tissue are very much elongated and therefore they are called as fibers. The muscle cells are specialized cells as they have got the property for contraction, as they are shorten and thickened actively. This property is due to presence of specialized contractile element, the myofibril, in the cytoplasm of muscle cells. CLASSIFICATION OF MUSCLES Muscle tissue may be classified as Morphological classification (based on structure) There are two types of muscle based on the morphological classification system 1. Striated Skeletal muscle Cardiac muscle 2. Non striated or smooth Smooth muscle CLASSIFICATION OF MUSCLES Functional classification There are two types of muscle based on a functional classification system 1. Voluntary Skeletal muscle 2. Involuntary Cardiac muscle Smooth muscle Properties of Skeletal Muscle Skeletal muscle consists of very long tubular cells (also called muscle fibers). Skeletal muscle fibers contain many peripherally placed nuclei. Skeletal muscle fibers show in many preparations characteristic cross- striations. It is therefore also called striated muscle. Properties of Skeletal Muscle Skeletal muscle is innervated by the somatic nervous system. Skeletal muscle makes up the voluntary muscle. HISTOLOGY OF SKELETAL MUSCLE • The striated skeletal muscle cell is an elongated multinucleate cell, which is commonly called a "muscle fiber". The cytoplasm (also called sarcoplasm) of the fiber is packed with longitudinal myofibrils, and also contains numerous mitochondria, a smooth-surfaced endoplasmic reticulum (called the sarcoplasmic reticulum), a small Golgi complex. The term sarcolemma refers to the plasma membrane of the muscle cell. UNITS OF MUSCLE CELLS whole muscle if made up of many smaller bundles known as fascicles. Each fascicle is made up of many muscle cells (myofibers). Myofibers contain cylindrical bundles of myofibrils which in turn contain many smaller bundles of myofilaments (Actin & Myosin). DIFFERENT UNIT OF SKELETAL MUSCLE Myofilament- Actin Myofilament- Myosin SKELETAL MUSCLES ARRANGEMENT OF MYOFILAMENTS A muscle cell or fiber is of consists a several myofibrils. Myofibrils are composed of individual contractile proteins called myofillaments. These myofilaments are generally divided into thick and thin myofilaments. The thin myofilaments are composed mainly of a protein known as actin. The thick myofilaments are composed mainly of the protein myosin. It is the orderly overlapping of the actin and myosin filaments that give cardiac and skeletal muscle their striated appearance (light and dark bands). Properties of Cardiac Muscle Cardiac muscle consists of muscle cells with one centrally placed nucleus. Nuclei are oval, and located centrally in the muscle cell. Cardiac muscle is innervated by the autonomic nervous system. Cardiac muscle exhibits cross- striations. Cardiac muscle is also called involuntary striated muscle. HISTOLOGY OF CARDIAC MUSCLE Although equal in ultra structure to skeletal muscle, the cross-striations in cardiac muscle are less distinct. In contrast to skeletal muscle cells, cardiac muscle cells often branch at acute angles and are connected to each other by specializations of the cell membrane in the region of the intercalated discs. Intercalated discs invariably occur at the ends of cardiac muscle cells HISTOLOGY OF CARDIAC MUSCLE This is a longitudinal section of cardiac muscle. The yellow arrows are indicating the Cardiac muscle fiber. It is different from muscle fibers in a couple ways. It is made up of more than one cell, it is not very symetrical and has intercelated discs. The blue arrows are pointing to the structure that gives away that this is a section of cardiac muscle which is the centrally located nuclei. yellow arrow - Cardiac Muscle Fiber Blue arrow - Centrally located nuclei CARDIAC MUSCLE Cardiac muscle closely resembles skeletal muscle, but has certain special features. Cardiac muscle is composed of separate cells and that intercalated discs are the sites of their end-to-end attachment. Cardiac muscle is striated but, unlike skeletal striated muscle, it is made up of a continuous, morphologically distinct network of branching and anastomosing cells. Cardiac muscle, like striated muscle, has actin and myosin microfilaments. Cardiac cells has centrally placed nucleus Properties of Smooth Muscle Smooth muscle consists of spindle shaped cells of variable size. The largest smooth muscle cells occur in the uterus during pregnancy. The smallest are found around small arterioles. Smooth muscle cells contain one centrally placed nucleus. The innervation of smooth muscle is provided by the autonomic nervous system. Centrally Located Smooth muscle makes up the Nucleus visceral or involuntary muscle. STRUCTURE OF SMOOTH MUSCLE Smooth muscle cell are described as spindle shaped. That is they are wide in the middle and narrow to almost a point at both ends. Smooth muscle cells have a single centrally located nucleus. Smooth muscle cells do not have visible striations although they do contain the same contractile proteins as skeletal and cardiac muscle, these proteins are just laid out in a different pattern. SMOOTH MUSCLE Smooth muscle is found in the walls of many hollow organs, Like the small intestine, the urinary bladder, uterus, arteries and veins. The cytoplasm of the tapered smooth muscle cell contains longitudinally arranged myofilaments. Smooth Muscle fibers • The green arrow is showing the Width of the smooth muscle tissue. While the yellow arrows are pointing to the nuclei of the smooth muscle cells. • Yellow Arrow - Nuclei of Smooth Muscle Cell • Green Arrow - Width of Smooth Muscle Tissue NERVOUS SYSTEM Nervous System The Nervous System consists of two types of cells the “Excitable Cells” the Neurons and “Supporting Cells” Glial Cells. Neurons are the structural and functional units of nervous system. About 100 million neurons present in nervous system. Neurons connected to each other like electric circuit, they can generate the impulse and propagate to other nerve cells. Glial Cells, the supporting cells the they are present between neuron act like the insulator and perform a number of functions in nervous system Anatomical Division of Nervous system Central Nervous System • Brain • Spinal Cord Peripheral Nervous System • Peripheral Nerves • Ganglia NEURONS Nerve cells or neurons, are responsible for the reception, transmission, and processing of stimuli; triggering of certain cell activities; release of neurotransmitters and gathering the informations. Different Parts of a Neuron: • Dendrites, have the multiple processes, specialized to stimuli from environment, sensory epithelial cells, or other neurons • Cell Body or Perikaryon, the trophic center for the whole cells and receives the stimuli. • Axon, a single Process specialized in generating or conducting nerve impulses to other cells, like Nerve, muscle and gland cells. AXON Axons may receive the informations from other Neuron, this informations only modified the transmission of action potential to other neurons. The distal part of axon is usually branched and constitutes Terminal Aborization. Each branch of this aborization terminates on the next cell in dilatation called End Bulbs or Boutons, which interact with other neurons or non-nerve cells, forming physiological communication, the Synapses. Synapses transmit information to next cell in the circuit. Structure of Neuron Neuron and their processes are variable in size and shape. The cell bodies can be spherical, ovoid or angular. Some of neuron are very large, measuring up to 150 mm in diameter. Other nerve cells are smallest nerve cells in the body, measuring 4-5 mm. Calcification of Neuron on the Basis of Number of Processes • Unipolar Neurons: Have only one Process. e.g. Mesencephalic Nucleus of V Nerve, Amacrine cells • Pseudo- unipolar neurons; Have got single processes which divided into a Peripheral and a Central Processes. e.g. Dorsal Root ganglia and Sensory ganglion of Trigeminal Nerve • Bipolar Neurons: have two Processes one each pole of cell body. e.g. Bipolar Neurons of Special Senses • Multi-polar Neurons: have got many Processes out of which one long, the axon and remaining the dendrites. e.g. most of the neurons of the body, Anterior Horn cells, Purkinje cells, Pyramidal cells. Calcification of Neuron on the Basis of Function • Motor (efferent) Neurons: control the organs such as muscles fibers, and exocrine and endocrine glands. • Sensory (afferent) Neurons: are involved in the reception o sensory Stimuli from the environment and from within body. • Interneurons: Establish relationship among other neurons, forming complex network. Calcification of Neuron on the Basis of Length of Axons • Golgi Type I Neurons: have got many Dendrites and very long Axon, take part in formation of Peripheral nerve. e.g. are pyramidal cells of cerebral cortex and anterior horn cells of the Spinal Cord. • Golgi Type II Neuron: have got many branched dendrites and short neuron. These neurons are numerous in cerebral and cerebellar cortices. Most of the Inter-neurons are Golgi type II variety. CELL BODY OR PERIKARYON Cell body is the part of neuron that contains the Nucleus and surrounding the cytoplasm without cell processes. The cell body is the trophic center maintaining integrating of all parts of Neuron. The Perikaryon of most of neuron receives a great number of nerve endings that convey excitatory or inhibitory stimuli generated in other nerve cells. Most of nerve cells have a spherical, larger, pale staining nucleus with prominent nucleolus. Binuclear nerve cells are seen in sympathetic and sensory ganglia. The chromatin is finely dispersed, reflecting the intense synthetic activity of these cells. CELL BODY OR PERIKARYON The cell body contains highly developed Rough Endoplasmic Reticulum organized into aggregates of parallel Cisternae. In the cytoplasm between cisternae are numerous polyribosomes, suggesting that the cells synthesize and both structural proteins and proteins for transport. When appropriate stains are used, Rough Endoplasmic reticulum and free Ribosomes appear under the light microscope as basophilic Granular areas called as NISSL BODIES. The number of Nissl bodies varies according to type of neuron and functional state. They are abundant in large nerve cell such as Motor neurons.
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