TISSUES

1. TISSUES UNIT 3

2. I. Types of Tissues • Epithelial tissue • Covers body surfaces • Lines hollow organs, body cavities and ducts • Forms glands

3. Connective tissue • Protects and supports the body and its organs • Bind organs together • Store energy reserves as fat • Help provide immunity to disease-causing organisms

4. Muscular tissue • Generates the physical force needed to make body structures move

5. Nervous tissue • Detects changes in a variety of conditions inside and outside the body • Responds to changes by generating nerve impulses • Nerve tissue in the brain helps maintain homeostasis

7. 1. EPITHELIAL TISSUE • Consists of cells arranged in continuous sheets • in either single or multiple layers • There is little intercellular space between adjacent cells

8. A. Epithelial surfaces • Apical surface: the free surface that faces the “outside” The most superficial layer

9. Lateral surface: faces the adjacent cells • Basal surface: opposite the apical surface adhered to extracellular materials The deepest layer

11. B. Types of Epithelium • Covering and lining: form the outer covering of the skin and some internal organs also forms the inner lining of blood vessels, ducts and body cavities and the interior of many organ systems

12. a. Classification of covering and lining cells • C & L cells are classified according to two characteristics: • Arrangement of cells into layers • Cell shape

13. i. Arrangement in layers • Arranged in one or more layers depending on the function performed

14. Simple Epithelium • A single layer of cells that function in diffusion, osmosis, filtration, secretion (production and release) and absorption (intake)

15. Stratified Epithelium • Two or more layers of cells that protect underlying tissues • Found in locations of considerable wear and tear

16. ii. Cell shape • Squamous cells: thin and arranged like floor tiles allowing for the rapid movement of substances through them occur in cells in which diffusion or infiltration occurs

17. Cuboidal cells • Are as tall as they are wide • Shaped like cubes…or hexagons • May have microvilli on apical surface • Function in secretion or absorption

18. Columnar cells • Taller than they are wide • Protect underlying tissue • Apical surface may have microvilli or cilia • Function in secretion or absorption

19. Transitional cells • Cells that change shape from cuboidal to flat or visa versa • This occurs as organs stretch or collapse

24. Glandular Epithelium constitutes the secreting portion of glands such as: thyroid, adrenal and sweat glands. They are highly specialized to make and secrete products.

25. Most glandular epithelium can be classified based on how their products are distributed to the body: • Endocrine: secreted into extracellular spaces • Exocrine: secreted into ducts

26. 2. CONNECTIVE TISSUE • One of the most abundant and widely distributed tissues • Performs a variety of functions: • binds together, supports and strengthens other body tissues

27. protects and insulates internal organs • compartmentalizes structures such as skeletal muscles • is the major site of immune responses • is the major transport system (as blood is a fluid connective tissue)

28. Consists of cells and an extracellular matrix which is located between the widely spaced cells and consists of protein fibers and ground substance (the stuff between the cells and the fibers)

29. The ground substance: • supports cells, • binds cells together • stores water • provides a medium for exchange of materials between the blood and cells

30. Types of fibers include collagen fibers, elastic fibers and reticular fibers. They strengthen and support ct. • Collagen fibers are found in most types of ct and are made of the protein collagen. This is the most abundant protein in the body!

31. Collagen is used extensively in tissue repair • It is flexible but resists stretching which is important when structures need to be held stationary. It is the main component in scar tissue formed during the healing process

32. Reticular fibers provide support and resist physical stress. • Elastic fibers provide elasticity and extensibility: they are able to stretch and return to their original shape. Scar tissue does not contain elastic fibers!

33. Classification of CT I. Embryonic ct • Mesenchyme (tissue from which all ct arises) • Mucous ct (mainly in the umbilical cord)

34. Mesenchymal cells give rise to all tissue cells • The immature forms of tissue cells are • Fibroblasts (CT), chondroblasts (cartilage) and osteoblasts (bone)

35. Immature “blast” cells are able to divide and secrete the matrix of its tissue. • Mature “cyte” cells have a reduced capacity for cell division and are more involved in matrix maintenance

36. II. Mature ct A. Connective tissue proper (CTP) 1. Loose or Areolar ct 2. Adipose tissue 3. Reticular ct

37. CTP contains: • Extracellular fibers • Ground substance • Either fixed or wandering cells

38. Extracellular fibers support and bind other tissues • Ground substance holds body fluids providing a reservoir of water and salts for surrounding tissue. Inflammation/edema occurs when the areolar tissue soaks up excess fluid and swells.

39. Fixed cells are stationary and are responsible for local tissue maintenance and repair as well as energy storage

40. Fixed cells: • Fibroblasts: production and maintenance of CT fibers • Fixed macrophages: engulf damaged cells or pathogens that enter tissue • Adipocytes

41. Mesenchymal cells: stem cells that respond to injury or infection. They divided to produce daughter cells that become any CT cell • Melanocytes: provide tissue with dark color…found in CT of eyes as well as epithelium

42. Wandering cells can move to various location depending on the local conditions. They are primarily responsible for defense and repair of damaged tissue. Their numbers change as conditions necessitate.

43. Free macrophages: wander in response to infection. • Mast cells: found near blood vessels…their cytoplasm is filled with granules of histamine and heparin. They stimulate inflammation in response to injury and/or infection

44. Lymphocytes: increase in number when tissue damage occurs. Some of them become plasma cells which produce antibodies. • Microphages: a small number respond to chemicals released by the fixed macrophages and mast cells

45. B. Dense connective tissue: supports and connects body parts • Dense regular ct: collagen fibers are arranged parallel to one another, packed tightly and aligned with the forces applied to them.

46. Examples include: • Tendons: connect muscles to bones • Aponeuroses • Elastic tissue • Ligaments

47. 2. dense, irregular ct 3. elastic ct (found in the walls of blood vessels and lining respiratory passageways)

48. C. Supporting CT 1. Cartilage a. Hyaline cartilage b. Fibrocartilage c. Elastic cartilage

49. Areolar connective tissue is the most widely distributed ct and is the only kind that occurs on an external surface and is the tissue that lines joint cavities • Loose ct is located beneath epithelia, around organs and around capillaries.

50. C.T. is usually highly vascular therefore has a rich blood supply