1. Chapter 2 Epithelium

2. What is epithelium?
Conception: Epithelium is a tissue composed of closely aggregated polyhedral cells and very little extracellular matrix.
Distribution: Cells cover body surfaces, line body cavities, and constitute glands.

3. 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

4. 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.

5. 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.

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

7. ---distribution: Three types:
1.mesothelium: the simple squamous epi. which line the inner surface of body cavities such as thoracic, pericardiac and abdominal cavities.
2. endothelium: the simple squamous epi. which line the inner surface of cardiovascular and lymphatic system.
3. other place: alveoli, parietal layers of renal capsule.

8. Mesothelium on abdominal cavity

9. Vascular endothelium

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

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

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

13. ---distribution: gastrointestinal tract gallbladder uterus
---function: secretion and absorption
goblet cell: scattered, secreting granules-mucinogen granules-mucus
simple columnar epi
goblet cell
striated border

14. 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 membrane : Simple epi.
four types of cells

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

16. 5) Stratified squamous epi.:
Three layers
---structural features:
1. Deepest (basal) cells: one layer of cuboidal cells
2. The cells in intermediate regions: several layers of polygonal –shaped cells
3. To the surface: more and more flattened cells

17. non-keratinised: mouth, pharynx, esophagus, and vagina
---distributon:
non-keratinised: mouth, pharynx, esophagus, and vagina
keratinised: the surface of body, make up the skin
non-keratinised
keratinised

18. keratinised
non-keratinised

19. 6) Transitional epi.: Two condition:
flexible-including the number of layers and shape of cells
Two condition:
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.

20. in the contracted bladder
in the distended bladder

21. ---distribution: Urinary tract (ureters, bladder, urethra)
The surface cells are very large and cuboidal in shape,
covering several deep cells.
Superficial cells

22. Summary 1 General feature of ep.:
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)  ---no blood vessels
---rich in nerve terminals
4) Having many functions

23. According to the number of layer and shape of cells
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.

24. 4. Epithelial specializations

25. Specialisations of free surface
specializations of the lateral surface
specialization of basal surface

26. 1) Specialisations of free surface
Microvilli
Cell coat
Cilia

27.      ①    microvilli:
defination: Microvilli are finger-like cytoplasmic projection on the free surface of most epithelial cells.
Distribution: striated border: intestinal epi. cell
brush border: proximal renal tubule

28. 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
Function:
increase the surface areas

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

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

31. ---structure:
5-10um long, 0.2um in diameter
surface: cell membrane
core: microtubules, 9X2+2
basal body: centrioles-connected with microtubules

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

34. 2) specializations of the lateral surface

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

36. junctional structures
Tight junction (zonula occludens)
Intermediate junction (zonula adherens)
Gap junction (communication junction)
Desmosome (macula adherens)

37. ① Tight junction (zonula occludens):
---structure:
apical part
point-liked fused between adjacent cells
form anastomosing network
---function: seal the space between cells

38. 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

39. ③ 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

41. ---structure: ④desmosome(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

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

43. 3) specialization of basal surface

44. 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

45. ---function:
support, connection, fixation
semi-permeable membrane
induce the movement, proliferation and differentiation of epi. cell

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

47. 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.

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

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

50. 1)classification:
exocrine gland: discharge the secretion through a duct system
endocrine gland: release the secretion directly into blood steam, no duct system

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

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

54. 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

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

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

57. Questions 1. Describe the characteristics of epithelial tissue
2. Compare the structure of microvilli with cilia

58. The composition of final score:
1. Lecture and Lab attendence: 10 %
2. Quiz: 15% （3 quizes，each quiz 5%）
3. Lab test: 25%
4. Final written examination：50%
Histology： 35-40%
Embryology：10-15%
*. If you want to pass this course:
final written examination score must be more than 50 and
final score>60
Preparation of laboratory work
Have the tools ready:
Pencils (red-blue pencil)
rubber, ruler and so on

59. Thanks!