1. Tissue

2. Tissue • Tissue - A group of closely associated cells that are similar in structure and perform related functions • Four primary types • Epithelium • Connective tissue • Nervous tissue • Muscle

3. Tissue • Epithelium: epithe = laid on, covering

4. Epithelial Tissue • Boundary: covers body surface or lines a body cavity (i.e.: digestive and respiratory) • Forms parts of most glands *Nearly all substances given or received by the body must pass through epithelium

5. Epithelial Tissue • Functions of epithelium • Protection: body’s first line of defense • Absorption – gas exchange • Ion transport • Filtration • Secretion – sweat, digestive juices, mucous, lubricant • Sensory input: skin, nose, eyes, ears

6. Special Characteristics of Epithelia CELLS, CELLS, CELLS • Cellularity –close/tight fit cells, forming sheets, bound at many points & separated by minimal extra cellular material • Specialized contacts - esp tight j’ns & desmosomes • Polarity - cell regions of the apical surface differ from the basal surface

7. Special Characteristics of Epithelia • Polarity • Apical surface - unattached, exposed to body’s exterior or organ cavity – often slick or covered w/cilia or villi • Basal surface – anchors to basement membrane

8. Special Characteristics of Epithelia 3 layers of basement membrane • Secreted by both epithelium & connective tissue • Functions • Filters molecules from capillaries entering epithelium • Anchors epithelium to underlying connective tissue • Non-cellular • Lamina lucida + Lamina densa = Basal lamina • Extracellular matrix composition varies: clear, delicate, structureless sheet, includes proteins • Lamina reticularis • Collagenous/protein fibers

11. Special Characteristics of Epithelia Basal surface/Basement membrane epithelia Lamina lumina Basal lamina Lamina densa Reticular fibers Lamina reticularis Anchoring fibers Anchoring plaque

12. Apical surface features • Microvilli – fingerlike extensions of plasma membrane • Abundant in small intestine and kidney • Maximize surface area across which small molecules enter or leave • Act as stiff knobs that resist abrasion

13. Cilia • Whiplike, highly motile extensions of apical surface membranes • Microtubules in cilia – arranged similarly to cytoplasmic organelles called centrioles • Movement of cilia – in coordinated waves Figure 4.8

14. Special Characteristics of Epithelia • Support by connective tissue • Avascularnutrients diffuse from underlying connective tissue • Innervated infiltrated with nerves • Regeneration - lost cells are quickly replaced by cell division if well nourished

15. Classifications of Epithelia • Classification includes 2 names (except transitional) • First name of tissue indicates number of cell layers • Simple – one layer of cells • Stratified – more than one layer of cells (named for cells at free/apical surface)

16. Classifications of Epithelia • Last name describes cell shape • Squamous (“scale-” or plate-like) • Hexagonal cells are wider than tall • Nuclei: central & flat (bumps in cross section) • Very little cytoplasm

17. Classifications of Epithelia • Last name of tissue describes shape of cells • Cuboidal • Cells are as wide as tall • Nuclei: large, central, round • May have microvilli, cilia

18. Classifications of Epithelia • Last name of tissue describes shape of cells • Columnar • Cells are taller than they are wide • Round to oval nuclei, near base • May have microvilli, cilia

19. Unicellular Exocrine Glands: Goblet Cells • Goblet cells - unicellular exocrine glands that produce mucin • Mucin + water  mucus • Protects and lubricates many internal body surfaces • May be embedded in epithelial tissue

20. Unicellular Exocrine Glands: Goblet Cells

21. Simple Squamous Epithelium • Description – single layer, flat cells • Function • Diffusion • Filtration • Friction reduction: secretes lubricating substances in serosae • Location • Endothelium: Lines heart, blood & lymph vessels • Mesothelium: Lines serous membranes - peritoneal, pleural, pericardial cavities • Covers visceral organs (3 major body cavities) • Small ducts, alveoli, loops of Henle (kidney) • Inner surface of eardrum

22. Simple Squamous Epithelium

23. Simple Squamous Epithelium

24. Simple Cuboidal Epithelium • Description - single layer of cube-like cells • Function - secretion and absorption • Location – kidney tubules, secretory portions of small glands & ducts (thyroid, salivary, pancreas), ovary surface

25. Simple Cuboidal Epithelium

26. Simple Columnar Epithelium • Description – single layer of column-shaped, some w/microvilli, goblet cells • Function • Absorption • Secretion of mucus, enzymes, and other substances • Ciliated type propels mucus or reproductive cells by ciliary action

27. Simple Columnar Epithelium • Nonciliated - digestive tract [stomach (protects stomach from acid) to anus], gallbladder, ducts of some glands • Microvilli (ABSORB!) & goblet cells (secrete mucous)

29. Simple Columnar Epithelium • Ciliated form - • In respiratory tract, goblet cells are interspersed among ciliated columnar epithelia of bronchi • Secreted mucus on the surface traps inhaled foreign particles. Beating cilia moves particles to the throat for removal by coughing, swallowing, or sneezing • Cilia also moves oocytes to the uterine tubes

30. Simple Columnar Epithelium • Ciliated form - small bronchi, fallopian tubes

31. Simple Columnar Epithelium

32. Simple Columnar Epithelium

33. Pseudostratified Columnar Epithelium • Description • All cells originate at basement membrane, but only tall cells reach the apical surface • May contain goblet cells and bear cilia • Nuclei lie at varying heights within cells, giving false impression of stratification

34. Pseudostratified nonciliated columnar epithelium • Nonciliated – no cilia, no goblet cells • Location: ducts of epididymis, vas deferens, urethra, ducts of large glands

35. Pseudostratified nonciliated Columnar Epithelium

36. Pseudostratified nonciliated Columnar Epithelium

37. Pseudostratified Ciliated Columnar Epithelium • Ciliated (MOST) – cilia & goblet cells • Location: lines trachea and most of upper respiratory tract

38. Pseudostratified Ciliated Columnar Epithelium

39. Pseudostratified Ciliated & Nonciliated Columnar Epithelium

40. Stratified Epithelia • Properties • Regenerate from basal layer • Major role is protection – more layers

41. Stratified Squamous Epithelium • Description • Most common stratified epithelial tissue • Thickest epithelial tissue, adapted for protection from abrasion • Base layers are metabolically active • Deeper layers of cells appear cuboidal or columnar • Cells dehydrate (become squamous), harden, die as pushed toward apical surface

42. Stratified Squamous Epithelium • Two types • Keratinized – forms epidermis, surface cells are dead and full of keratin, a protective protein, waterproof • Nonkeratinized - forms moist lining of body openings of mouth, esophagus, rectum, vagina,

43. Stratified Squamous Epithelium Figure 4.3e

44. Stratified Squamous Epithelium Figure 4.3e

45. Stratified Squamous Epithelium Figure 4.3e

46. Stratified Cuboidal Epithelium • Description – rare in humans; generally two layers of cube-shaped cells • Function – protection, secretion • Location • Egg-producing vesicles (ovaries) • Sperm -producing ducts (seminiferous tubules) • Forms ducts of • Mammary glands • Salivary glands • Largest sweat glands

47. Stratified Cuboidal Epithelium Figure 4.3f

48. Stratified Cuboidal Epithelium Figure 4.3f

49. Stratified Cuboidal Epithelium Figure 4.3f

50. Stratified Cuboidal Epithelium Figure 4.3f