Tissues

1. Tissues

2. Tissues • Groups of cells that share a similar function are called tissues. There are many types of tissues that are designed to perform a variety of functions.

4. Epithelial Tissues • Characteristics: • Sheets of cells that line the body’s surface or a body cavity. • Surface of cell exhibits polar properties. Exposed surface called apical surface. Anchored surface is called basal surface. Most apical surfaces have microvilli.

5. Designed to fit close together. Includes tight junctions and desmosomes. Tight junctions keep proteins in the apical region from diffusing to the basal region, thus maintaining polarity.

6. Epithelial sheets are usually supported by connective tissues. • Avascular (no blood vessels) but innervated (infused with nerve tissues). • Highly regenerative.

7. Types of Epithelium • Simple: Single cell layer. • Stratified: more than one cell layer.

8. Squamous • Flattened scale-like cells.

9. Cuboidal • Cube shaped, as wide as it is tall.

10. Columnar • Long Column shaped cells.

11. Simple Squamous Epithelium • Structure: • Single layer of flattened cells with disc shaped central nucleus and sparse cytoplasm. • Function: • Allows passage of materials by diffusion and filtration in sites where protection is not important, secretes lubricating substances into serosae.

12. Simple Squamous Epithelium

13. Simple Cuboidal Epithelium • Structure: • Single layer of cube like cells with large spherical central nucleus. • Function: • Secretion and absorption.

14. Simple Cuboidal Epithelium

15. Simple Columnar Epithelium • Structure: • Single layer of tall cells with round and oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands. • Function: • Absorption; secretion of mucus, enzymes, and other substances, ciliated types propel muscles and sometimes reproductive cells, through ciliary action.

16. Simple Columnar Epithelium

17. Pseudostratified Columnar Epithelium • Structure: • Single layer of cells of differing heights. Some not reaching the surface. Nuclei seen at different levels; may contain mucus-secreting cells and bear cilia. • Function: • Secretion, particularly of mucus; propulsion of mucus by ciliary action.

19. Stratified Squamous Epithelium • Structure: • Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous). Squamous cells shouldn’t just be found, usually always anchored to other cell types. • Function: • Protects underlying tissue areas subject to abrasion.

21. Stratified columnar&stratified cuboidal epithelium • Structure: • Thick multi-layered tissues. Usually junctions between other epithelium. Rare in the human body. • Function: • supports for other tissues. Usually found in ducts or glands.

22. Columnar Cuboidal

23. Transitional Epithelium • Structure: • Looks like stratified squamous and stratified cuboidal. Basal cells cuboidal or columnar; surface cells dome shaped or squamous like. • Function: • Stretches readily and permits distension of urinary organ by contained urine.

25. Glandular Epithelia • Glands- one or more cells that secrete or make a particular product. Things secreted are called secretions. Usually always aqueous.

26. Endocrine Glands • Endocrine glands produce hormones. • There are too many to go into detail on right now because they all vary in size, shape, and function. • (whole chapter devoted to this later on)

27. Exocrine glands • Numerous and vary in function. • All secrete on the surface of the skin or in a body cavity. • We will discuss these more when we cover integument.

28. Connective tissue • Most abundant of the tissues. • Four main classes of connective tissues: • Blood • Connective tissue proper • Cartilage • Bone tissue

29. Characteristics of Connective Tissue • Common origin: all come from mesinchyme (an embryonic tissue) • Degrees of vascularity: range from avascular (cartiladge), to highly vascularized (bone) • Extracellular matrix: nonliving tissues form the extracellular matrix. Can bear pressure, withstand tension, and handle abuse.

30. Functions of connective tissue • Functions: • Binding and support • Protection • Insulation • Transportation (blood)

31. Structural Elements of Connective tissue • Ground substance: fills gaps b/w cells and contains fibers. Made of interstitial fluid, cell adhesion proteins and proteoglycans.

32. Fibers: provide support. • Collagen fibers- made of collagen, provide strength. • Elastic Fibers: made of protein elastin, rubbery, and allows connective tissues to snap back to place after tension is relieved in the tissue. • Reticular fibers: collagen like fibers that form networks that then form around blood vessels.

33. Cells: • Fibroblasts-forms connective tissue proper • Chondroblasts- cartilage • Osteoblasts- forms bone cells • Hematopeotic stem cells- undifferentiated blood blast cell.

34. Connective tissue proper: loose connective tissue, areolar • Structure: • Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells. • Function: • Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid.

36. Connective tissue proper: loose connective tissue, adipose • Structure: • Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet. • Function: • Provides reserve food fuel; insulates against heat loss; supports and protects organs.

38. Connective tissue proper: loose connective tissue, reticular • Structure: • Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network. • Function: • Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.

40. Connective tissue proper: dense connective tissue, dense regular • Structure: • Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast. • Function: • Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile strength when pulling force applied in one direction.

42. Connective tissue proper: dense connective tissue, dense irregular • Structure: • Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast. • Function: • Able to withstand tension exerted in many directions; provide structural strength.

44. Connective tissue proper: dense connective tissue, elastic • Structure • Dense irregular connective tissue containing a high proportion of elastic fibers. • Function • Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following respiration.

46. Hyaline Cartilage • Structure: • Amorphus but firm matrix; collagen fibers form an imperceptible (hard to perceive) network; chondroblasts produce the matrix and when mature, will lie in lacunae. • Function: • Support and reinforce, resist compression.

48. Elastic Cartilage • Structure: • Like hyaline cartilage, but more elastic. • Function: • Maintains structure while allowing great flexibility. (like your ear)

50. Fibrocartilage • Structure: • Matrix similar to but less firm than hyaline cartilage. Has thick collagen fibers. • Function: • Tensile strength with the ability to absorb compressive shock.