Tissues

Tissues: Epithelial, connective, muscular and nervous tissues, their types and characteristics.

1. TISSUES By Gladys Stephen M.Pharm

2. TISSUES A tissue is a group of 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 The tissues in the human body contribute to homeostasis by providing diverse functions including protection, support Communication among cells, and resistance to disease By Gladys Stephen M.Pharm

3. TYPES OF TISSUES Body tissues can be classified into four basic types according to structure and function: Epithelial tissue Connective tissue Muscular tissue Nervous tissue By Gladys Stephen M.Pharm

4. Epithelial tissue: Covers body surfaces and lines hollow organs, body cavities, and ducts. It also forms glands. Connective tissue: 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 disease-causing organisms. Muscular tissue: Generates the physical force needed to make body structures move and generates body heat. Nervous tissue: Detects changes in a variety of conditions inside and outside the body and responds by generating action potentials (nerve impulses) that activate muscular contractions and glandular secretions. By Gladys Stephen M.Pharm

5. CELL JUNCTIONS Most epithelial cells and some muscle and nerve cells are tightly joined into functional units. Cell junctions are contact points between the plasma membranes of tissue cells. five main types of cell junctions are Tight junctions Adherens junctions Desmosomes Hemidesmosomes Gap junctions By Gladys Stephen M.Pharm

6. Epithelial Tissue Consists of cells arranged in continuous sheets, in either single or multiple layers. The cells are closely packed and are held tightly together by many cell junctions, there is little intercellular space between adjacent plasma membranes. Epithelial tissue forms coverings and linings throughout the body. It is never covered by another tissue, so it always has a free surface. Epithelial tissues have three major functions: Selective barriers that limit or aid the transfer of substances into and out of the body; Secretory surfaces that release products produced by the cells onto their free surfaces; and Protective surfaces that resist the abrasive influences of the environment. By Gladys Stephen M.Pharm

7. Apical (free) Lateral surfaces surface Epithelium Basal lamina Connective tissue Basement membrane Reticular lamina Basal surface Nerve Blood vessel By Gladys Stephen M.Pharm

8. The basement membrane is a thin extracellular layer consists of two layers basal lamina and Reticular lamina The basal lamina (lamina thin layer) is closer to—and secreted by—the epithelial cells It contains proteins such as laminin and collagen, as well as glycoproteins and proteoglycans. Laminin molecules adhere to integrins in hemidesmosomes and thus attach epithelial cells to the basement membrane. The reticular lamina is closer to the underlying connective tissue and contains proteins such as collagen produced by connective tissue cells called fibroblasts By Gladys Stephen M.Pharm

9. Epithelial tissue has its own nerve supply, but is avascular . The blood vessels that bring in nutrients and remove wastes are located in the adjacent connective tissue. Exchange of substances between epithelium and connective tissue occurs by diffusion. Epithelial tissue plays many different roles in the body; the most important are protection, filtration, secretion, absorption, and excretion. In addition, epithelial tissue combines with nervous tissue to form special organs for smell, hearing, vision, and touch . By Gladys Stephen M.Pharm

10. Epithelial tissue may be divided into two types. 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. Glandular epithelium makes up the secreting portion of glands such as the thyroid gland, adrenal glands, and sweat glands. Endocrine gland Exocrine gland By Gladys Stephen M.Pharm

11. Covering and Lining Epithelium Classified according to two characteristics: arrangement of cells into layers shapes of the cells Arrangement of cells into layers Simple epithelium Pseudostratified epithelium Stratified epithelium Based on the shapes of the cells Squamous cells Cuboidal cells Columnar cells Transitional cells By Gladys Stephen M.Pharm

12. Simple Pseudostratified Stratified Squamous Cuboidal Columnar Cell shape Arrangement of layers By Gladys Stephen M.Pharm

13. T ypes of covering and lining epithelia are as follows : I . Simple epithelium A. Simple squamous epithelium B. Simple cuboidal epithelium C. Simple columnar epithelium (nonciliated and ciliated) D. Pseudostratified columnar epithelium (nonciliated and ciliated) II. Stratified epithelium A. Stratified squamous epithelium (keratinized and nonkeratinized)* B. Stratified cuboidal epithelium* C. Stratified columnar epithelium* D. Transitional epithelium By Gladys Stephen M.Pharm

14. Simple Squamous Epithelium Description : Single layer of flat cells; centrally located nucleus. Location : 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 membranes, such as the peritoneum, pericardium, and pleura. Function : Filtration, diffusion, osmosis, and secretion in serous membranes. By Gladys Stephen M.Pharm

15. Peritoneum Nucleus of simple squamous cell Cytoplasm Plasma membrane Surface view of simple squamous epithelium of mesothelial lining of peritoneum Small intestine Flat nucleus of simple squamous cell Connective tissue Muscular tissue Simple squamous cell Basement membrane Connective tissue By Gladys Stephen M.Pharm

16. Simple Cuboidal Epithelium Description: Single layer of cube-shaped cells; centrally located nucleus. Location: Covers surface of ovary, lines anterior surface of capsule of the lens of the eye, forms the pigmented epithelium at the posterior surface of the eye, lines kidney tubules and smaller ducts of many glands, and makes up the secreting portion of some glands such as the thyroid gland and the ducts of some glands such as the pancreas. Function: Secretion and absorption. By Gladys Stephen M.Pharm

17. Sectional view of simple cuboidal epithelium of intralobular duct of pancreas Pancreas Duodenum Connective tissue Nucleus of simple cuboidal cell Lumen of duct Simple cuboidal epithelium Simple cuboidal epithelium Connective tissue Basement membrane Simple cuboidal cell By Gladys Stephen M.Pharm

18. Nonciliated Simple Columnar Epithelium Description: Single layer of nonciliated column-like cells with nuclei near base of cells; contains goblet cells and cells with microvilli in some locations. Location: Lines the gastrointestinal tract (from the stomach to the anus), ducts of many glands, and gallbladder. Function: Secretion and absorption. By Gladys Stephen M.Pharm

19. Small intestine Mucus in goblet cell Sectional view of nonciliated simple columnar epithelium of lining of jejunum of small intestine Nucleus of goblet cell Basement membrane Nonciliated simple columnar epithelium Nonciliated simple Columnar epithelium By Gladys Stephen M.Pharm

20. Ciliated Simple Columnar Epithelium Description: Single layer of ciliated column-like cells with nuclei near base; contains goblet cells in some locations. Location: Lines some bronchioles (small tubes) of respiratory tract, uterine (fallopian) tubes, uterus, efferent ducts of the testes, some paranasal sinuses, central canal of spinal cord, and ventricles of the brain. Function: Moves mucus and other substances by ciliary action. By Gladys Stephen M.Pharm

21. Cilia Mucus in goblet cell Basement membrane Connective tissue Ciliated simple columnar epithelium Uterine tube By Gladys Stephen M.Pharm

22. Pseudostratified columnar epithelium Description: 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 . By Gladys Stephen M.Pharm

23. Trachea Pseudostratified ciliated columnar epithelium Ciliated columnar cell Pseudostratified ciliated columnar epithelium Cilia Mucus in goblet cell By Gladys Stephen M.Pharm

24. Stratified squamous epithelium Description: Several layers of cells; cuboidal to columnar shape in deep layers; squamous cells form the apical layer and several layers deep to it; cells from the basal layer replace surface cells as they are lost. Location: Keratinized variety forms superficial layer of skin; nonkeratinized variety lines wet surfaces, such as lining of the mouth, esophagus, part of larynx, part of pharynx, and vagina, and covers the tongue. Function: Protection. By Gladys Stephen M.Pharm

25. Vagina Flattened squamous cell at apical surface Stratified squamous epithelium Basement membrane Connective tissue By Gladys Stephen M.Pharm

26. Stratified cuboidal epithelium Description : 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 . Function : Protection and limited secretion and absorption. By Gladys Stephen M.Pharm

27. Esophagus Stratified cuboidal epithelium Stratified cuboidal epithelium By Gladys Stephen M.Pharm

28. Stratified columnar Epithelium Description : 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. By Gladys Stephen M.Pharm

29. Stratified columnar epithelium Esophagus Stratified columnar epithelium By Gladys Stephen M.Pharm

30. Transitional Epithelium Description : 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 distension. By Gladys Stephen M.Pharm

31. Urinary bladder Relaxed transitional epithelium Transitional epithelium By Gladys Stephen M.Pharm

32. Glandular Epithelium The function of glandular epithelium is secretion, which is accomplished by glandular cells that often lie in clusters deep to the covering and lining epithelium. A gland may consist of a single cell or a group of cells that secrete substances into ducts (tubes), onto a surface, or into the blood. All glands are classified into Endocrine glands Exocrine glands By Gladys Stephen M.Pharm

33. Endocrine Glands Description: Secretory products (hormones) diffuse into blood after passing through interstitial fluid. Location: Examples include pituitary gland at base of brain, pineal gland in brain, thyroid and parathyroid glands near larynx (voice box), adrenal glands superior to kidneys, pancreas near stomach, ovaries in pelvic cavity, testes in scrotum, and thymus in thoracic cavity. Function: Produce hormones that regulate various body activities. By Gladys Stephen M.Pharm

34. Thyroid gland Endocrine gland (thyroid gland) Hormone-producing (epithelial) cell Stored precursor of hormone By Gladys Stephen M.Pharm

35. Exocrine Glands Description: Secretory products released into ducts. Location: Sweat, oil, and earwax glands of the skin; digestive glands such as salivary glands, which secrete into mouth cavity, and pancreas, which secretes into the small intestine. Function: Produce substances such as sweat, oil, earwax, saliva, or digestive enzymes. By Gladys Stephen M.Pharm

36. Exocrine gland (sweat gland) Skin Skin Lumen of duct of sweat gland Basement membrane Nucleus of secretory cell of sweat gland Secretory portion of sweat gland By Gladys Stephen M.Pharm

37. CONNECTIVE TISSUE most abundant and widely distributed tissues in the body. has a variety of functions. It binds together, supports, and strengthens other body tissues; protects and insulates internal organs; compartmentalizes structures such as skeletal muscles; serves as the major transport system within the body (blood, a fluid connective tissue); is the primary location of stored energy reserves (adipose, or fat, tissue); and is the main source of immune responses. By Gladys Stephen M.Pharm

38. General Features of Connective Tissue Consists of two basic elements: Extracellular matrix and cells Extracellular matrix is the material located between its widely spaced cells. It consists of protein fibers and ground substance, the material between the cells and the fibers. It is secreted by the connective tissue cells and determines the tissue’s qualities. E.g. in cartilage, the extracellular matrix is firm but pliable. But the extracellular matrix of bone, by contrast, is hard and inflexible. Do not usually occur on body surfaces, are highly vascular. By Gladys Stephen M.Pharm

39. Connective Tissue Cells The types of connective tissue cells are Fibroblasts Adipocytes Mast cells White blood cells Macrophages Plasma cells By Gladys Stephen M.Pharm

40. Reticular fiber Fibroblast Eosinophil Mast cell Neutrophil Plasma cell Adipocyte Blood vessel Ground substance Elastic fiber Collagen fiber Macrophage By Gladys Stephen M.Pharm

41. Extracellular Matrix The extracellular matrix consists of two major components: (1 ) ground substance (2) fibers. Ground substance is the component of a connective tissue between the cells and fibers. It may be fluid, semifluid, gelatinous, or calcified. supports cells, binds them together, stores water, and provides a medium through which substances are exchanged between the blood and cells. It plays an active role in how tissues develop, migrate, proliferate, and change shape, and in how they carry out their metabolic functions. By Gladys Stephen M.Pharm

42. FIBERS Three types of fibers are embedded in the extracellular matrix between the cells: Collagen fibers Elastic fibers Reticular fibers By Gladys Stephen M.Pharm

43. Classification of Connective Tissues I . Embryonic connective tissue A. Mesenchyme B. Mucous connective tissue II. Mature connective tissue A. Loose connective tissue 1. Areolar connective tissue 2. Adipose tissue 3. Reticular connective tissue B. Dense connective tissue 1. Dense regular connective tissue 2. Dense irregular connective By Gladys Stephen M.Pharm

44. C. Cartilage 1. Hyaline cartilage 2. Fibrocartilage 3. Elastic cartilage D. Bone tissue E. Liquid connective tissue 1. Blood tissue 2. Lymph By Gladys Stephen M.Pharm

45. Embryonic connective tissue Embryo Sectional view of mesenchyme (connecting tissue ) Ground substance Nucleus of mesenchymal cell Reticular fiber By Gladys Stephen M.Pharm

46. Mucous connective tissue Umbilical Cord Foetus Mucous connective tissue By Gladys Stephen M.Pharm

47. CARTILAGE Hyaline Cartilage Description: Consists of a bluish-white, shiny ground substance with thin, fine collagen fibers 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. By Gladys Stephen M.Pharm

48. Foetus Sectional view of hyaline cartilage of a developing foetal bone and details of several chondrocytes skeleton By Gladys Stephen M.Pharm

49. Fibrocartilage Description: Consists of chondrocytes scattered among thick bundles of collagen fibers within the extracellular matrix. Location: Pubic symphysis (point where hip bones join anteriorly), intervertebral discs (discs between vertebrae), menisci (cartilage pads) of knee, and portions of tendons that insert into cartilage. Function: Support and fusion . By Gladys Stephen M.Pharm

50. Portion of right lower limb Sectional view of fibrocartilage of tendon Tendon of quadriceps femoris muscle By Gladys Stephen M.Pharm

51. Elastic cartilage Description: Consists of chondrocytes located in a threadlike network of elastic fibers within the extracellular matrix. Location: Lid on top of larynx (epiglottis), part of external ear (auricle), and auditory (eustachian) tubes. Function: Gives support and maintains shape. By Gladys Stephen M.Pharm

52. ELASTIC CARTILAGE Auricle of ear Sectional view of elastic cartilage of auricle of ear By Gladys Stephen M.Pharm

53. BONE TISSUE Compact Bone Description: Compact bone tissue consists of osteons (haversian systems) that contain lamellae, lacunae, osteocytes, canaliculi, and central (haversian) canals. By contrast, spongy bone tissue (see Figure 6.3 on page 180) 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. By Gladys Stephen M.Pharm

54. Femur Details of an osteocyte By Gladys Stephen M.Pharm

55. LIQUID CONNECTIVE TISSUE Blood Description: Consists of blood plasma and formed elements: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Location: Within blood vessels (arteries, arterioles, capillaries, venules, and veins) and within the chambers of the heart . Function: Red blood cells transport oxygen and some carbon dioxide; white blood cells carry on phagocytosis and are involved in allergic reactions and immune system responses; platelets are essential for the clotting of blood. By Gladys Stephen M.Pharm

56. Blood smear Platelet White blood cell (leukocyte) Red blood cell (erythrocyte) Blood plasma By Gladys Stephen M.Pharm

57. MUSCULAR TISSUE consists of elongated cells called muscle fibers or myocytes that can use ATP to generate force . muscular tissue produces body movements, maintains posture , and generates heat It also provides protection . By Gladys Stephen M.Pharm

58. Based on its location and certain structural and functional features, muscular tissue is classified into three types: Skeletal muscle tissue Cardiac muscle tissue Smooth muscle tissue By Gladys Stephen M.Pharm

59. SKELETAL MUSCLE TISSUE Description: 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. By Gladys Stephen M.Pharm

60. Cardiac muscle Tissue Description : Branched striated fibers with one or two centrally located nuclei; contains intercalated discs; involuntary control. Location: Heart wall. Function: Pumps blood to all parts of the body. By Gladys Stephen M.Pharm

61. SMOOTH MUSCLE CELL Description: Spindle-shaped (thickest in middle and tapering at both ends), nonstriated fibers 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 , gallbladder , urinary bladder, and uterus. Function: Motion (constriction of blood vessels and airways, propulsion of foods through gastrointestinal tract, contraction of urinary bladder and gallbladder). By Gladys Stephen M.Pharm

62. NERVOUS TISSUE Consists of only two principal types of cells: neurons and neuroglia (glial cells). Neurons, or nerve cells, are sensitive to various stimuli. They convert stimuli into electrical signals called action potentials (nerve impulses) and conduct these action potentials to other neurons, to muscle tissue, or to glands. Most neurons consist of three basic parts: a cell body and two kinds of cell processes— dendrites and axons. By Gladys Stephen M.Pharm

63. Neuron of spinal cord Axon Dendrite Nucleus By Gladys Stephen M.Pharm

64. GLIAL CELLS non-Neuronal cells Maintains homeostasis, forms myelin and provides support and protection for neurons in central and peripheral nervous systems. The types of glial cells in CNS are Oligodendrocytes Astrocytes Ependymal cells Microglia The types of glial cells in CNS are Schwann cells Satellite cells By Gladys Stephen M.Pharm

65. GLIAL CELLS Ependymal cells astrocytes Microglial cells oligodendrocytes By Gladys Stephen M.Pharm

66. FAQs Write notes on: Enumerate the functions of epithelial tissue Characteristic features of muscular tissues Give the classification of connective tissue. What are its functions? Name the primary tissues. Give the salient features of any one of them. Connective tissues. By Gladys Stephen M.Pharm