1. Chapter 2 Epithelium

2. 1.General feature:
1) contain more cells and less extracellular ground substance
2) Polarisaton:
---free surface: face air or other things
---basal surface: have basement membrane, to
face underlying connective tissue (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, e.g. 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

33. 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
terminal web

34. cilia
Tight junction
desmosome
intermediate junction

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

37. connexons

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. Under EM:
--basal lamina: nm, electron-dense, thread-liked and amorphous ground substance, produced by epi. cell
--reticular lamina: reticular tissue + ground substance, produced by CT

42. ---function:
support, connection, fixation
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 renal tubule 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
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

54. √ Multichosen question
1.The lining epithelium of the serous body cavities (pericardial, pleural and peritoneal) is
endothelium
mesothelium
simple cuboidal epithelium
stratified squamous epithelium
transitional epithelium √

55. √ 2. An endocrine gland passes its secretion directly into the
blood or lymph
duct
body surface
digestive tract
lumen of acinus √

56. 3. The nucleus is flattened against the basal plasma memberane of the cells, the cytoplasm is filled with large mucigen droplets, it is the
serous cell
mucous cell
serous demilune
goblet cell
myoepithelial cell √

57. Fill in the blanks Hematoxylin Eosin
In H.E. stain sections, the cytoplasm is stained pink by ___________, the nucleus is stained purple-blue by___________________________.
Hematoxylin
Eosin

58. The procedure of preparation of histologic slides includes mainly______________________, ___________,_________________,
_____________, ______________,and sectioning.
Obtaining the specimen
Fixation
Dehydration
Clearing
Embedding

59. The 4 basic types of tissue are ______________,_________________,_________________ and _________________.
epithelium
connective tissue
muscular tissue
nervous tissue

60. Epithelia are mainly classified into 2 groups: ______________and_______________.
Simple epi.
Stratified epi

61. The intercellular junctions of epithelial cells are (1) _______________,
(2) ___________________,
(3) _____________, and (4)______________. When 2 or more kinds of them are present together, we called it __________________.
Tight junction
Intermediate junction
Desmosome
Gap junction
Junctional complex

62. 7. Specialized structures on basal surface of epithelial cells are ________________________________,_____________________________ and ______________________.
basement membrane
plasma membrane infolding
hemidesmosomes

63. 8. Pseudostratified columnar ciliated epithelium consists of 4 kinds of cells with different shape and height, but all set on the basal membrane: ________________________,
________________,_____________and ________________.
columnar cell (ciliated)
goblet cell
fusiform cell
basal cell

64. Questions Describe the characteristics of epithelial tissue.
Describe the structural characteristics and functions of each covering epithelial type.
Compare the structure of microvilli with cilia.
Compare the structure of intermediate junction with desmosome.