1. Chapter 2 Epithelium

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

3. 2.Classification of Epithelium
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. According to the number of layer and shape of cells
3. Classification of 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. Vascular endothelium

8. Mesothelium on abdominal cavity

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

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

11. 3)      simple columnar epi.:
---structural features:
one layer of columnar cells, with basally located ovoid nucleus

12. ---distribution: gastrointestinal tract gall bladder uterus
---function: secretion and absorption
goblet cell: scattered, secreting granules-mucinogen granules-mucus
goblet cell
simple columnar epi

13. 4) pseudostratified ciliated columnar epi.:
---Structural feature:
1, Four types of cells
columnar cell (ciliated); goblet cell
fusiform cell; basal cell:pyramid-shaped
2, Every cell locate on basement membrance: Simple epi.
four types of cells

14. ---distribution: inner surface of large duct of respiratory trachea
bronchi
nasal
The epithelium of trachea

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

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

17. 6)      transitional epi.:
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.

18. ---distribution: bladder

19. in the contracted bladder
in the distended bladder

20. 4. Epithelial specializations

21. 1) Specialisations of free surface

22.      ①    microvilli:
---defination: delicate finger-liked projections of cell-membrane and cytoplasm protruding from the free surface

23. ---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

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

25. ② cell coat:
---defination: a thick layer of extracellular glycoprotein
---function: adherence, supporting, protection, exchange of material and recognize

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

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

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

30. 2) specializations of the lateral surface

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

32. 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

34. 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

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

36. 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

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

39. 3) specialization of basal surface

40. 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

41. EM:
--basal lamina: nm, electron-dense, thread-liked and amorphous ground substance, produced by epi. Cell
--reticular lamina: RT+ground substance, produced by CT

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

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

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

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

46. 5. Glandular epi. and gland
glandular epi.: epi are specialized for secretion
gland: organs composed mainly of glandular epi.

47. 1)classification:
exocrine gland: discharge the secretion through a duct system
endocrine gland: release the secretion directly into blood steam

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

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

51. flattened dark nucleus against the basal cell membrane
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

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

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