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Tissue level of organization.pdf

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Tissue level of organization.pdf

  1. 1. Tissue level of organization BY: Dr. Tanvi H. Desai (M.Pharm, Ph.D)
  2. 2. Introduction • A tissue is a group of similar cells that usually have a common embryonic origin and function together to carry out specialized activities. • Tissues may be hard (bone), semisolid (fat) or even liquid (blood) in their consistency. • Histology is the science that deals with the study of tissues. • Pathologist is a physician who specializes in laboratory studies of cells and tissues to help other physicians to make accurate diagnosis. • He examines tissues for any changes that might indicate disease.
  3. 3. Types of tissues and their origins • On the basis of structure and function, body tissues can be classified into four basic types: • 1. Epithelial tissue: It covers body surfaces and lines hollow organs, body cavities, and ducts. Glands are also formed by it. • 2. Connective tissue: It protects and supports the body and its organs. Various types of connective tissue bind organs together, store energy reserves as fat, and help provide immunity to pathogens. • 3. Muscular tissue: It generates the physical force needed to make body structures move.
  4. 4. • 4. Nervous tissue: It detects changes in a variety of conditions inside and outside the body and responds by generating action potentials (nerve impulses) that help maintain homeostasis. • All tissues of the body develop from three primary germ layers that differentiate in the human embryo called the ectoderm, endoderm and mesoderm. • Epithelial tissues develop from all three primary germ layers. • All connective tissue and most muscle tissues derive from mesoderm. • Nervous tissue develops from ectoderm.
  5. 5. Epithelial tissue • The subtypes of epithelia include covering and lining epithelia and glandular epithelia. • An epithelium consists mostly of cells with little extracellular material between adjacent plasma membranes. • The apical, lateral and basal surfaces of epithelial cells are modified various ways to carry out specific functions. • Epithelium is arranged in sheets and attached basement membrane. • Although it is avascular, it has a nerve supply. • Epithelia are derived from all three primary germ layers and have a high capacity for renewal.
  6. 6. • Epithelial layers can be simple (one layer) or stratified (several layers). • The cell shapes may be squamous (flat), cuboidal (cube like), columnar (rectangular), or transitional (variable). • Epithelial tissue may be divided into two types. (1) Covering and lining epithelium forms the outer covering of the skin and some internal organs. • It also forms the inner lining of blood vessels, ducts, and body cavities, and the interior of the respiratory, digestive, urinary, and reproductive systems. (2) Glandular epithelium makes up the secreting portion of glands such as the thyroid gland, adrenal glands, and sweat glands.
  7. 7. 1. Covering and Lining Epithelium • According to arrangement of cells into layers and shapes of the cells, the types of covering and lining epithelia are as follows: • A Simple Epithelium • 1. Simple Squamous Epithelium: It consists of single layer of flat cells having centrally located nucleus. • Location: It lines heart, blood vessels, lymphatic vessels, air sacs of lungs, glomerular (Bowman's) capsule of kidneys, and inner surface of the tympanic membrane (eardrum), forms epithelial layer of serous (lubricating) membranes, such as the peritoneum (tissue of abdomen wall). • Function: Filtration (eg., kidneys), diffusion (eg., oxygen in lungs) osmosis, and secretion in serous membranes.
  8. 8. • 2. Simple Cuboidal Epithelium: It consists of single layer of cube-shaped cells having centrally located nucleus. • Location: It covers surface of ovary, lines kidney tubules and smaller duct of many glands, and make up the secreting portion of some glands like thyroid gland and the ducts of some glands, eg., the pancreas. • Function: It performs the function of secretion and absorption.
  9. 9. 3. Simple columnar epithelium: • The cells of simple columnar epithelium appear like columns (taller than they are wide), with oval nuclei near the base. • Simple columnar epithelium exists in two forms: (I) Non ciliatedsimple columnar epithelium (II) Ciliated simple columnar epithelium. • I: Nonciliated Simple Columnar Epithelium: It consists of single layer of nonciliated column like cells with nuclei near base of cells. • It contains goblet cells (the primary site for nutrient digestion and mucosal absorption) and cells with microvilli in some locations. • Location: It lines the gastrointestinal tract, ducts of many glands, and gall bladder. • Function: Secretion and absorption.
  10. 10. • II. Ciliated Simple Columnar Epithelium: It consists of single layer of ciliated column like cells with nuclei near base; contains goblet cells in some locations. • Location: Lines a few portions of upper respiratory tract, uterine (fallopian) tubes, uterus, some paranasal sinuses, central canal of spinal cord, and ventricles of the brain. • Function: Moves mucus and other substances by ciliary action.
  11. 11. • 4. Pseudo-stratified Columnar Epithelium: It is not a true stratified tissue, nuclei of cells are at different levels; all cells are attached to basement membrane, but not all reach the apical surface. • Location: Pseudostratified ciliated columnar epithelium lines the airways of most of upper respiratory tract; pseudostratified nonciliated columnar epithelium lines larger ducts of many glands, epididymis, and part of male urethra. • Function: Secretion and movement of mucus by ciliary action.
  12. 12. B. Stratified Epithelium • 1. Stratified Squamous Epithelium : It consists of several layers of cells; layers possess cuboidal to columnar cells. • Squamous cells form the apical layer and several layers deep to it. • Cells from the basal layer replace surface cells as they are lost regularly. • Location: Keratinized variety forms superficial layer of skin; nonkeratinized variety lines wet surfaces, such as lining of the mouth, esophagus, part of the epiglottis, part of pharynx and vagina, and covers the tongue. • Function: Protection and limited secretion. • 2. Stratified Cuboidal Epithelium : It consists of two or more layers of cells in which the cells in the apical layer are cube shaped. • Location: Ducts of adult sweat glands and esophageal glands and part of male urethra.
  13. 13. • Function: Protection and limited secretion and absorption.
  14. 14. • 3. Stratified Columnar Epithelium : It consists of several layers of irregularly shaped cells; only the apical layer has columnar cells. • Location: Lines part of urethra, large excretory ducts of some glands, such as esophageal glands, small areas in anal mucous membrane, and part of the conjunctiva of the eye. • Function: Protection and secretion.
  15. 15. • 4. Transitional Epithelium: Its appearance is variable (transitional); shape of cells in apical layer ranges from squamous (when stretched) to cuboidal (when relaxed). • Location: Lines urinary bladder and portions of ureters and urethra. • Function: Permits distention (expansion).
  16. 16. Connective tissue • 1. Functions of Connective Tissue: Connective tissue is one of the most abundant and widely distributed tissues in the body. • In its various forms, connective tissue have a variety of functions :- • It binds together, supports and strengthens other body tissues. • It protects the internal organs. • It compartmentalizes structures such as skeletal muscles. • It serves as the major transport system within the body eg., blood and lymph. • It is the primary location of stored energy reserves (adipose or fat tissue). • It is the main source of immune responses.
  17. 17. • 2. General Features of ConnectiveTissue • Connective tissue consists of two basic elements: extracellular matrix and cells. • Connective tissue consists of relatively few cells and an abundant extracellular matrix (ECM) secreted by the widely spaced cells. • The ECM consists of protein fibres and ground substance (gel-like structure), and determines the tissue's qualities, eg., stable and flexible in cartilage but hard and inflexible in bone. • Connective tissue does not usually occur on free (body) surfaces. • It has a nerve supply (except for cartilage), and is highly vascular (except for cartilage, tendons, and ligaments).
  18. 18. 3. Classification of Connective Tissues: Connective tissues may be classified as follows: I. Embryonic connective tissue A. Mesenchyme B. Mucous connective tissue II. Mature connective tissues A. Loose connective tissue 1. Areolar connective tissue 1. Adipose tissue 1. Reticular connective tissue B. Dense connective tissue 1. Dense regular connective tissue 1. Dense irregular connective tissue 1. Elastic connective tissue C. Cartilage 1. Hyaline cartilage 1. Fibrocartilage 1. Elastic cartilage D. Bone tissue E. Liquid connective tissue 1. Blood tissue 1. Lymph
  19. 19. • I. Embryonic connective tissue A. Mesenchyme: It consists of irregularly shaped mesenchymal (proliferate) cells embedded in a semi fluid ground substance that contains reticular fibers. Location: skin and along developing bones of embryo; some mesenchymal cells occur in adult connective tissue, especially along blood vessels. Function: Forms all other types of connective tissue. B. Mucous Connective Tissue (Wharton's jelly): It consists of widely dispersed fibroblasts (having collagen and fibers) embedded in a viscous, jelly like ground substance that contains the collagen fibers. Location: Umbilical cord of fetus. Function: Support.
  20. 20. II. Mature Connective Tissue • A. Loose Connective Tissue • 1. Areolar Connective Tissue: It consists of fibres (collagen, elastic and reticular) and several kinds of cells (fibroblasts, macrophages, plasma cells, adipocytes, and mast cells) embedded in a semifluid ground substance. • Location: Subcutaneous layer deep to skin; papillary (superficial) region of dermis of skin; lamina propria of mucous membranes; and around blood vessels, nerves, and body organs. • Function: Strength, elasticity, and support.
  21. 21. • 2. Adipose Tissue: It consists of adipocytes, with a large centrally located droplet off triglycerides (fats); nucleus and cytoplasm are peripherally located. • Location: Subcutaneous layer deep to skin, around heart and kidneys, yellow bane marrow, and padding around joints and behind eyeball in eye socket. • Function: Reduces heat loss through skin, serves as an energy reserve, supports, and protects. In newborns, brown adipose tissue (BAT) generates considerable heat that helps to maintain proper body temperature.
  22. 22. • 3. Reticular Connective Tissue: It is a network of interlacing reticular fibres and reticular cells. • Location: Stroma (supporting framework) of liver, spleen, lymph nodes; red bone marrow, which gives rise to blood cells; reticular lamina of the basement membrane; and around blood vessels and muscles. • Function: Forms stroma (net like structure) of organs, binds together smooth muscle tissue cells, filters and removes worn out blood cells in the spleen and microbes in lymph nodes.
  23. 23. • B. Dense ConnectiveTissue • 1. Dense Regular Connective Tissue: Its extracellular matrix looks shiny white; consists mainly of collagen fibres arranged in bundles; fibroblasts present in rows between bundles. • Location: Forms tendons (attach muscle to bone), most ligaments (attach bone to bone),and aponeuroses (sheet like tendons that attach muscle to muscle or muscle to bone). • Function: Provides strong attachment between various structures. • 2. Dense Irregular Connective Tissue: It consists mainly of randomly arranged collagen fibres and a few fibroblasts.
  24. 24. • Location: Fasciae (tissue beneath skin and around muscles and other organs), reticular (deeper) region of dermis of skin, periosteum of bone, perichondrium of cartilage, joint capsules, membrane capsules around various organs (kidneys, liver, testes, lymph nodes), pericardium of the heart, and heart valves. • Function: Provides strength. • 3. Elastic Connective Tissue: It consists mainly of freely branching elastic fibres; fibrobalsts are present in spaces between fibres. • Location: Lung tissue, walls of elastic arteries, trachea, bronchial tubes, true vocal cords, suspensory ligament of penis, and ligaments between vertebrae. • Function: Allows stretching of various organs.
  25. 25. C. Cartilage: • Cartilage consists of a dense (thick) network of collagen fibres and elastic fibers firmly embedded in chondroitin sulphate, a gel-like component of the ground substance. • Cartilage can tolerate considerably more stress than loose and dense connective tissues. • The strength of cartilage is due to its collagen fibres, and its resilience (ability to assume its original shape after deformation) is due to chondroitin sulphate. • The cells of mature cartilage, called chondrocytes, occur singly or in groups within spaces called lacunae in the extracellular matrix. • A covering of dense irregular connective tissue called the perichondrium surrounds the surface of most cartilage.
  26. 26. • The perichondrium is composed of two layers: • an outer fibrous layer that consists of collagen fibers, blood vessels, and fibroblasts, and • an inner cellular layer that consists of cells involved in the growth of cartilage. • Unlike other connective tissues, cartilage has no blood vessels or nerves, except in the perichondrium. • Cartilage does not have a blood supply because it secretes an anti- angiogenesis factor, a substance that prevents blood vessel growth. • Because of this property, anti angiogenesis factor is being studied as a possible cancer treatment to stop cancer cells from promoting new blood vessel growth that supports their rapid rate of cell division and expansion. • Since cartilage has no blood supply, it heals poorly following an injury.
  27. 27. • 1. Hyaline Cartilage : It consists of a bluish-white, shiny ground substance with fine collagen fibres and many chondrocytes; most abundant type of cartilage. • Location: Ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, and embryonic and fetal skeleton. • Function: Provides smooth surfaces for movement at joints, as well as flexibility and support.
  28. 28. • 2. Fibrocartilage: It consists of chondrocytes distributed among bundles of collagen fibers within the extracellular matrix. • Location: Pubic symphysis (where hip bones join anteriorly), intervertebral discs, menisci (cartilage pads) of knee, and portions of tendons that insert into cartilage. • Function: Support and fusion. • 3. Elastic cartilage: It consists of chondrocytes located in a threadlike network of elastic fibres within the ECM. • Location: Lid on top of larynx (epiglottis), part of external ear (auricle), and auditory (eustachian) tubes. • Function: Gives support and maintains shape.
  29. 29. D. Bone Tissue • Compact bone: Compact(dense, solid) bone tissue consists of osteons (cylindrical vascular tunnels formed by an osteoclast-rich tissue- haversian systems) that contain lamellae, lacunae, osteocytes, canaliculi, and central (haversian) canals. • By contrast spongy bone an issue consists of thin columns called trabeculae; spaces between trabeculae are filled with red bone marrow. • Location: Both compact and spongy bone tissue make up the various parts of bones of the body. • Function: Support, protection, storage; houses blood forming tissue; serves as levers that act with muscle tissue to enable movement. • E. Liquid ConnectiveTissue: • 1. Blood: It consists of blood plasma and formed elements: red blood cells (erythroyctes), white blood cells (leukocytes), and platelets (thrombocytes).
  30. 30. • Location: Within blood vessels (arteries, arterioles, capillaries, venules and veins) and within the chambers of the heart. • Function: RBCs transport O2 and some CO2; WBCs carry on phagocytosis and are involved in allergic reactions and immune system responses; platelets are essential for the clotting of blood. • 2. Lymph: It consists of plasma like liquid component and lymphocytes as formed elements. • Location: Within lymphatic vessels. • Function: It is concerned with the defense of the body against infection. It also transports fats in the form of chylomicrons from intestine to blood circulation.
  31. 31. Muscular tissue • Muscular tissue consists of fibres that are specialized for contraction. • It provides motion, maintenance of posture, heat production and protection. • Classification • Based on its location and certain structural and functional features, muscular tissue is classified into 3 types - skeletal, cardiac, and smooth. • A. Skeletal Muscle Tissue: It consists of long, cylindrical, striated fibers with many peripherally located nuclei; voluntary control. • Location: Usually attached to bones by tendons. • Function: Motion, posture, heat production and protection.
  32. 32. • B. Cardiac Muscle Tissue: It consists of branched, striated fibers with one or two centrally located nuclei; contains inserted discs; involuntary control. • Location: Heart wall. • Function: Pumps blood to all parts of the body. • C. Smooth Muscles Tissue: It consists of spindle shaped (thickest in middle and tapering at both ends), nonstriated fibres with one centrally located nucleus; involuntary control. • Location: Iris of the eyes, walls of hollow internal structures such as blood vessels, airways to the lungs, stomach, intestines, gall bladder, urinary bladder, and uterus. • Function: Motion (constriction of blood vessels and airways, propulsion of food through GI tract, contraction of urinary bladder and gall bladder).
  33. 33. Comparison of different type of muscles: Characteristic Skeletal muscle Cardiac Muscle Visceral Muscle Location: Usually attached to bone Walls of heart Walls of visceral organs Nature: Under Control of will Voluntary muscles Under Control of ANS Involuntary muscles Not under Control of will Involuntary muscles Cell type: Long cylindrical fibres arranged in bundles short cylindrical fibres forming branch network Spindle shape fibres arranged in bundlesor sheets
  34. 34. Cell membrane: Distinct double layered sarcolemma Sarcolemma forms intercalated discs Delicate sarcolemma fused with adjacent fibres cytoplasm Sarcoplasm limited Organelles numerous Sarcoplasm large amount Organelles numerous Sarcoplasm small amount Organelles fewer myofibrils Striated Distinct longitudinal striations Striated Fewer than in skeletal muscle Non Striated Filament fill the cell
  35. 35. nuclei Multiple Flatted nuclei scattered over cell periphery just under sarcolemma One or two Oval At centre of each cell One oval or rod shape At centre of each cell Vascular supply Good blood supply Lymph capillaries restricted to epimysium and permysium Dense blood capillary beds Some lymph capillaries Fair supply of blood And lymph capillaries Nerve supply Somatic autonomic Autonomic
  36. 36. NERVOUS TISSUE AND ITS FUNCTIONS • It consist of the two principle kinds of cells: 1) neurons (nerve cells) and 2) neuroglia. • 1) Neurons: The neurons consists of three basic portion : • a) Cell body: Cell body contains a nucleolus surrounded by cytoplasm that includes typical organelles such as lysosomes, mitochondria and Golgi complex. • In the cytoplasm it also contains the Chromatophilic substance (Nissl bodies) which is ordinary arrangement of endoplasmic reticulum, the site of protein synthesis and it also contain neurofibrils which forms the cytoskeleton and provide the support and shape of the cells. • b) Dendrites: Dendrites are the receiving or input portion of the neurons. They are usually short, tapering (narrowing, pointed) and highly branched.
  37. 37. • Usually dendrites are not myelinated. Their cytoplasm contains chromatophilic substance, mitochondria and other organelles. c) Axon: It is a long, thin and cylindrical in shape. It is joined with cell body by axon hillock. • The first portion of axon is known as initial segment where the nerves impulse are arise. • It also contains mitochondria, microtubules and neurofibrils but no rough endoplasmic reticulum so it does not synthesize protein. • Its cytoplasm known as axoplasm which is surrounded by membrane known as axolema. • The side branch of axon is known as axon collaterals. • At the end of axon it divides branch like structure known as axon terminals. • The tip of some axon terminals swell in to bulb shaped known as synaptic end bulbs.
  38. 38. • Classification of neurons: • According to functional classification it is divided in to: • i) Sensory neurons or afferent neurons: It transmits nerve impulse from receptors of skin, sense organ, muscles, and joints into the CNS. • ii) Motor or Efferent Neurons: It conveys motor nerve impulse from the CNS to the effectors which may be either muscles or glands. • According to structural it can be classified in to : • i) Multi polar neurons: It has several dendrites and one axon. Most neurons of brain and spinal cord are of this type. • ii) Bipolar neurons: It has one main dendrites and one axon. It is found in the eye, inner ear and olfactory areas of the brain.
  39. 39. • iii) Unipolar neurons: It's originated as bipolar neurons in the embryo but during the development axon and body get fuse into a single process that divides in to two branch and consist one cell body. • It is always sensory neurons.
  40. 40. • 2) Neuralgia: Neuroglia or glia fills about half of the CNS. • Its have the glue like characteristics so it held nervous tissue together. • Neuroglias are generally smaller than neurons. • Neuroglia can multiply and divide in the mature nervous systems. • Classification of Neuroglia: There are mainly six types of Neuroglia in which four astrocytes, olegodendrocytes, microglia and ependymal cells are found in the CNS. • While neurolemmocytes (schwann cells) and satellite cells found in peripheral nervous system. • i) Astrocytes: They are star shaped. It produces the metabolism of neurotransmitters maintain the proper balance of K+ for generation of nerves impulse, and participate in brain development. • It forms the blood brain barrier which regulates entry of substance in to the brain.
  41. 41. • ii) Olegodendrocytes: It is the most common glial cells in the CNS. It is smaller than astrocytes. • They coil around neurons and produce supporting structure to the neurons. It produces protein and lipid covering known as myelin sheath. • iii) Microglia: It is the small and phagocytic Neuroglia derived from monocytes. They protect the CNS from the disease by engulfing invading microbes and clearing away debris from dead cells. • iv) Ependymal: It is the epithelial cells. The cells have different shaped from cuboidal to columnar and many are ciliated. Ependymal cells line the fluid filled ventricles, cavity within the brain and central canal means a narrow passage from spinal cord. It forms the fluid which is known as cerebrospinal fluids.
  42. 42. • b) Neuroglia found in peripheral nervous system: • i) Neurolemmocytes (schwann cells): Each cell produces myelin sheath around PNS Neurons. • ii) Satellite cells: Which supports neurons in ganglia in PNS. • Myelination: The axons of most mammalian neurons are surrounded by a multilayered lipids and proteins of Neuroglia and this covering is known as myelin sheath and the axon with such a covering are said to be a myelinated. • Whereas those without covering are known as unmyelinated axon. • The sheath electrically protects the axon of neurons and increases the speed of nerve impulse conduction.
  43. 43. • Function of Nervous tissue: • a) Sensory function: It sense certain changes both within body (the internal environment) such as stretching of your stomach or increase the acidity and out side the body (the external environment) such as rain drop landing on your arm or the aroma of rose. • b) Integrative Function: It analyzes the sensory information, store some aspect and make some decision regarding appropriate behavior. • c) Motor function: It may respond to stimuli by initiating muscular contraction or glandular secretion.

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