Body Tissues

1. Body Tissues Ch.3 (Part II)

2. Body Tissues • Cells are specialized for particular functions • Tissues • Groups of cells with similar structure and function • Four primary types • Epithelium • Connective tissue • Nervous tissue • Muscle

3. Body Tissues • If we had to assign a single term to each primary tissue type that would best describe its overall role, the terms would most likely be: • Covering (epithelium) • Support (connective) • Movement (muscle) • Control (nervous) • However, these terms only reflect only a tiny fraction of the functions that each of these tissues perform.

4. 1. Epithelial Tissues • Found in different areas • Body coverings • Body linings • Glandular tissue (forms glands in body) • Functions • Protection • Absorption • Filtration • Secretion

5. Special Characteristics of Epithelium: • Cells fit closely together (except for glandular) to form connective sheets • Tissue layer always has one free surface. This so called “apical surface” is exposed to the body’s exterior or to the cavity of an internal organ. • The lower surface of epithelium is bound by a basement membrane (a structure less material secreted by cells) • Avascular (have no blood supply) so they depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen • Regenerate easily if well nourished

6. Classification of Epithelium 1. Number of cell layers • Simple – one layer • Stratified – more than one layer Figure 3.17a

7. Classification of Epithelium 2. Shape of cells • Squamous – flattened (like fish scales) • Cuboidal – cube-shaped (like dice) • Columnar – column-like (like columns…duh) Figure 3.17b

8. Simple or Stratified… Simple Stratified Consist of two or more cell layers More durable than the simple epithelia Function primarily to protect • One layer of cells • Most concerned with absorption, secretion, and filtration • Because they are usually very thin, protection is not one of their specialties

9. Simple Epithelium • 1. Simple squamous • Single layer of flat cells • Usually forms membranes where filtration or exchange of substances by rapid diffusion occurs. • Lines body cavities • Lines lungs and capillaries Figure 3.18a

10. Simple Epithelium • 2. Simple cuboidal • Single layer of cube-like cells • Common in glands and their ducts • Forms walls of kidney tubules • Covers the ovaries Figure 3.18b

11. Simple Epithelium • 3. Simple columnar • Single layer of tall cells • Often includes goblet cells, which produce mucus • Lines the entire digestive tract from the stomach to the anus Figure 3.18c

12. Simple Epithelium • 4. Pseudostratified • Single layer, but some cells are shorter than others • Often looks like a double cell layer (false…hence the name pseudo) • Sometimes ciliated, such as in the respiratory tract • May function in absorption or secretion Figure 3.18d

13. Stratified Epithelium • 1. Stratified squamous • Cells at the free edge are flattened but closer to the basement membrane, are cuboidal or columnar • Found as a protective covering where friction/abuse is common • Locations • Skin • Mouth • Esophagus Figure 3.18e

14. Stratified Epithelium • 2. Stratified cuboidal • Two layers of cuboidal cells • 3. Stratified columnar • Surface cells are columnar, cells underneath vary in size and shape • Stratified cuboidal and columnar • Rare in human body • Found mainly in ducts of large glands

15. Stratified Epithelium • 4. Transitional epithelium • Shape of cells depends upon the amount of stretching (near basement: typically columnar or cuboidal, at surface: varies) • Lines organs of the urinary system like the bladder, ureters, and part of the urethra where considerable amounts of stretching occur. Figure 3.18f

16. Glandular Epithelium • Gland – one or more cells that secretes a particular product (secretion) • Two major gland types develop from epithelial sheets: • 1. Endocrine gland • Ductless (hormones diffuse directly into the blood vessels that weave through the glands) • Secretions are all hormones • Examples of endocrine glands: thyroid, adrenals, and pituitary • 2. Exocrine gland • Empty through ducts to the epithelial surface • Include sweat and oil glands, and liver and pancreas • Are both internal and external

17. Connective Tissue • Found everywhere in the body & connects body parts • Includes the most abundant and widely distributed tissues • Functions • Binds body tissues together • Supports the body • Provides protection

18. Connective Tissue Characteristics: • Variations in blood supply • Some connective tissue types are well vascularized (good blood supply) • Some have poor blood supply or are avascular like tendons and cartilages (these things heal slowly) • Extracellular matrix • Connective tissues are made up of many different types of cells plus varying amounts of non-living material that surrounds living cells (called the extracellular matrix)

19. Extracellular MatrixMakes connective tissue different from any other tissue. • Two main elements • Ground substance – mostly water along with adhesion proteins and polysaccharide molecules • Fibers • Produced by the cells • Three types • Collagen fibers • Elastic fibers • Reticular fibers

20. Extracellular Matrix Continued: • Allows connective tissue to • form a soft packaging tissue around other organs, • to bear weight, • and to withstand stretching and other abuses, such as abrasion that no other tissue could endure.

21. Connective Tissue Types: • Bone (osseous tissue) • Composed of: • Bone cells in lacunae (cavities) • Surrounded by a hard matrix of calcium salts • Large numbers of collagen fibers • Because of its rocklike hardness, bone is used to protect and support the body Figure 3.19a

22. Connective Tissue Types: • Hyaline cartilage • Most common cartilage (cartilage is found only in a few places in the body…is less hard and more flexible than bone.) • Composed of: • Abundant collagen fibers • Rubbery matrix • Blue-white appearance • Entire fetal skeleton is hyaline cartilage (turns to bone by birth)! • Also forms the supporting structure of the larynx (voicebox), attaches ribs to the breastbone, and covers the ends of bones where they form joints. Figure 3.19b

23. Connective Tissue Types: • Elastic cartilage • Provides elasticity • Example: supports the external ear

24. Connective Tissue Types: • Fibrocartilage • Highly compressible • Example: forms cushion-like discs between vertebrae Figure 3.19c

25. ConnectiveTissue Types: • Dense connective tissue • Main matrix element is collagen fibers • Cells are fibroblasts (fiber forming cells) • Forms strong ropelike structures (like the examples listed below) • Examples • Tendon – attach muscle to bone • Ligaments – attach bone to bone Figure 3.19d

26. Connective Tissue Types: • Areolar connective tissue • Most widely distributed connective tissue • Soft, pliable “cobwebby” tissue that cushions and protects the body organs • Helps hold internal organs together and in their proper positions • Contains all fiber types • Can soak up excess fluid Figure 3.19e

27. ConnectiveTissue Types: • Adipose tissue: Commonly called fat! • Matrix is an areolar tissue in which fat cells predominate • Many cells contain large lipid deposits • Functions • Insulates the body • Protects some organs • Serves as a site of fuel storage Figure 3.19f

28. Connective Tissue Types: • Reticular connective tissue • Delicate network of interwoven fibers • Forms stroma (internal supporting network) of lymphoid organs • Lymph nodes • Spleen • Bone marrow Figure 3.19g

29. Connective Tissue Types: • Blood (vascular tissue) • Blood cells surrounded by fluid matrix (called plasma) • Fibers are visible during clotting • Functions as the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, and many other substances throughout the body. Figure 3.19h

30. Muscle Tissue • Function is to produce movement • Three types • Skeletal muscle • Cardiac muscle • Smooth muscle

31. Muscle Tissue Types: • 1. Skeletal muscle • Can be controlled voluntarily • Form the muscular system • Cells attach to connective tissue • Cells are striated (striped) • Cells have more than one nucleus Figure 3.20a

32. Muscle Tissue Types • 2. Cardiac muscle • Found only in the heart • Function is to pump blood (involuntary) • Cells attached to other cardiac muscle cells at intercalated disks (have gap junctions …remember this mean info can pass freely from cell to cell….) • Cells are striated • One nucleus per cell • Under involuntary control Figure 3.20b

33. Muscle Tissue Types • 3. Smooth muscle • AKA: visceral muscle • Involuntary muscle • Surrounds hollow organs • Spindle-shaped (pointed at each end) • Attached to other smooth muscle cells • No visible striations (hence the name smooth) • One nucleus per cell Figure 3.20c

34. Nervous Tissue • Neurons and nerve support cells • Function is to send impulses to other areas of the body • Irritability • Conductivity Figure 3.21

35. Tissue Repair (Wound Healing) • Tissue repair occurs in two major ways… • 1. Regeneration • Replacement of destroyed tissue by the same kind of cells • 2. Fibrosis • Repair by dense fibrous connective tissue (scar tissue is formed) • Determination of method • Type of tissue damaged • Severity of the injury

36. Tissue injury sets a series of events into motion… • Capillaries become very permeable • Introduce clotting proteins • Wall off injured area • Formation of granulation tissue • Regeneration of surface epithelium

37. Regeneration of Tissues • Tissues that regenerate easily • Epithelial tissue • Fibrous connective tissue and bone • Tissues that regenerate poorly • Skeletal muscle • Tissues that are replaced largely with scar tissue • Cardiac muscle • Nervous tissue within the brain and spinal cord Read about Homeostatic Imbalance on pg. 98 and make notes….