1. Chapter 2 Epithelium

2. 1.General feature: 1) contain more cells and less extracellular ground substance 2) Polarisaton: ---free outer surface: face air or other things ---basal surface: face underlying CT, havebasement membrane 3) Avascularity,but innervation: ---no blood vessels ---rich in nerve terminals 4) Having functions of protection, secretion, absorption excretion and sensory reception

3. 2.Classification 1) Covering epithelium: the epithelium which cover body surface or line the inner surface of body cavities, tubes and sac. 2) Glandular epithelium: the epithelium which main function is secretion. 3) Sensory epithelium: the epithelium which has special sensory function.

4. 3.Covering epithelium : According to the number of layer and shape of cells Simple epi.: ---simple squamous epi. ---simple cuboidal epi. ---simple columnar epi. ---pseudostratified ciliated columnar epi. Stratified epi.: ---stratified squamous epi. ---stratified columnar epi. ---transitional epi.

5. 1) simple squamous epi: ---structural feature: /one layer flattened cells, cell border are interdigitate /with flattened ellipsoid nucleus

6. ---distribution: mesothelium: the simple squamous epi. which line the inner surface of body cavities such as thoracic, pericardiac and abdominal cavities. endothelium: the simple squamous epi.which line the inner surface of cardiovascular and lymphatic system. other place: alveoli,parietal layers of renal capsule. ---function: a) transport of materials b) facilitates movement of viscera

7. 2) simple cuboidal epi.: ---structural feature: one layer of cells, with same height and width(in side view) and hexagonal outline in surface view. spherical centrally-located nucleus

8. ---distribution: /the renal tubule /thyroid /the some ducts of mang glands ---main function: covering and secretion

9. 3) simple columnar epi.: ---structural features: one layer of columnar cells,with basally lacated ovoid nucleus goblet cell: scattered, secreting granules- mucinogen granules-mucus

10. ---distribution: /gastrointestinal tract /gall bladder /uterus ---function: secretion and absorption

11. 4) pseudostratified ciliated columnar epi.: ---structural feature: four types of cells /columnar cell:ciliated /fusiform cell /basal cell:pyramid-shaped /goblet cell

12. ---distribution: inner surface of large duct of respiratory /trachea /bronchi /nasal

13. 5) stratified squamous epi.: ---structural features: deepest(basal)cells: one layer of cuboidal cells intermediate regions:several layers of polygonal – shaped cells to the surface: more and more flattened

14. ---distributon: non-karatinised:mouth,pharynx, oesophagus, urethra and vagina karatinised: the surface of body, make up the skin

15. 6) transitional epi.: ---structural feature: flexible-including the number of layers and shape of cells in the distended bladder: there are two to three layers of cells. The cells become flattened. in the contracted bladder : there are six to seven layers of cells. The surface cells are very large and cuboidal in shape, covering several deep cells. ---distribution: bladder

16. 4. Epithelial specializations

17. 1) Specialisations of free surface

18. ① cell coat: ---defination: a thick layer of extracellular glycoprotein ---function: adherence, supporting, protection, exchange of material and recognize

19. ② microvilli: ---defination: delicate finger-liked projections of cell-membrane and cytoplasm protruding from the free surface

20. ---structure: 0.1um in diameter, with different longth. surface: cell membrane with cell coat core: longitudinal microfilament-actin filament fixed on terminal web terminal web: made up of transverse-arranged filament at the apical side of cells

21. ---function: increase the surface areas ---distribution: /striated border: intestinal epi.cell /brush border: proximal renal tubule

22. ③ cilia: ---defination: elongated, mobile projections of cell membrane and cytoplasm protruding from free surface

23. ---structure: 5-10um long, 300-500nm in diameter surface: cell membrane core: microtubules, 9X2+2, dynein basal body: centrioles-connected with microtubules

24. ---function: swing to produce a forward-moving wave ---distribution: epithelial cells of respiratory tract

25. 2) specializations of the lateral surface

26. ---intercellular connection of adjacent cells: non-special: the minute space and cadherin-cell adherent molecules special: junctional structures

27. ① Tight junction( zonula occludens): ---structure: apical part point-liked fused between adjacent cells arranged in 2-4 thread-liked structures form anastomosing network ---function: seal the space between cells

28. ② intermediate junction(zonula adherens): ---structure: below the tight junction a gap of 15-20nm in width with medium electron-density filament material plaque of electron-dense materials, with attached microfilament-make up of terminal web ---function: /adherens /keep the cell shape /transfer cell contract force

29. ③ desmosome(macula adherens): ---structure: plate or spot-shaped a gap of 20-30 nm, with low electron-density filaments interdigitate to form intermediate line attachment plaque: with attached tonofilament(10nm)- intermediate filament(karatin) ---function: firmly connection

30. ④ gap junction(communicating junction): ---structure: the smallest gap of 2-3 nm connexons: -consist of protein -7~9nm in diameter -composed of 6-subunits of proteins- connexin -2nm channel: hydrophilic channel ---function: provide a pathway between cells

32. *junctional complex: four types of junctional structures(at least two types) get together.

33. 3) specialization of basal surface

34. ① basement membrane: ---defination: a sheet of membrane-liked amorphous material interposed between epi.cells and underlying CT. ---structure: HE: pink colour, hard to see

35. EM: three layers --lamina lucida: 10-50 nm, electron-lucent --basal lamina: 20-300 nm, electron-dense, thread-liked and amorphous ground substance, produced by epi. Cell --reticular lamina: RT+ground substance, produced by CT glycoprotein: laminin, type IV collagen, heparin sulfate proteoglycan and fibronectin

36. ---function: support, connection, fixaton semi-premeable membrane induce the movement, proliferation and differentiation of epi.cell

37. ② plasma membrane infolding(basal longitudinal striation): ---defination: the infolding of cell-membrane with many mitochondria at the basal surface of epi.cell

38. ---function: increase the basal surface areas facilitate the passage of water and ions ---distribution: mainly in proximal and distal renal tubule.

39. ③ hemidesmosomes ---is half of desmosome.

40. 5. Glandular epi. and gland glandular epi.: epi are specialized for secretion gland: organs composed mainly of glandular epi. 1)classification: exocrine gland: discharge the secretion through a duct system endocrine gland: release the secretion directly into blood steam

41. 2) structure of exocrine gland: ① acinus(secreting unit): according the nature of secretion a. serous acinus: serous secretory cells

42. ---structure: pyramid-shaped cell basally-located round nucleus acidophilic cytoplasm-eosinophilic zymogen granules-contain enzymes EM: RER,Golgi complex ---function: produce a serous secretion

43. b. mucous acinus: mucous secreting cells ---structure: pyramid-shaped cell flattened dark nucleus against the basal cell membrane slightly basophilic cytoplasm-large mucigen granules EM: some RER, Golgi complex ---function: secretes mucus

44. c. mixed acinus: two types of cells ---structure: mucous acinus with several serous cells attach on one side- serous demilune

45. ② ducts: ---from simple squamous epi to simple columnar or stratified epi. ---carry out the secretions ---secrete or absorb water and ions