1 Epithelial Tissue 上皮组织 Jun Zhou ( 周俊 ) School of Medicine, Zhejiang University

2 General feature 1) More cells and less extracellular ground substance 2) Polarisaton: ---free outer surface: face air or other things ---basal surface: face underlying CT, have basement membrane 3) Avascularity, but innervation: ---no blood vessels ---rich in nerve terminals 4) Functions: protection, secretion, Absorption, excretion and sensory reception

3 Classification  Covering epithelium( 被覆上皮 ): cover body surface or line the inner surface of body cavities, tubes and sac.  Glandular epithelium( 腺上皮 ): the epithelium which main function is secretion.  Sensory epithelium( 感觉上皮 ): the epithelium which has special sensory function.

4 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 simple squamous epi.( 单层扁平上皮 )  one layer flattened cells, cell border are interdigitate  flattened ellipsoid nucleus

6 Distribution:  mesothelium( 间皮 ): body cavities  endothelium( 内皮 ): cardiovascular and lymphatic system.  other place: alveoli, parietal layers of renal capsule. Function: a) transport of materials b) facilitates movement of viscera

7 Simple cuboidal epi. （单层立方上皮 ）  one layer, cuboidal, hexagonal outline  spherical centrally-located nucleus Distribution: Renal tubule Thyroid some ducts of glands Function: covering and secretion

8  one layer, columnar, basally located ovoid nucleus  Goblet cell （杯状细胞） : scattered, secreting granules- mucinogen granules-mucus Distribution: gastrointestinal tract gall bladder uterus Function: secretion and absorption Simple columnar epi.( 单层柱状上皮）

9 Four types of cells  columnar cell:ciliated  fusiform cell  basal cell:pyramid-shaped  goblet cell Distribution: Respiratory system Pseudostratified ciliated columnar epi. （假复层纤毛柱状上皮）

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11  Basal cuboidal cells---polygonal -----flattened Distribution:  non-keratinized: mouth, pharynx, esophagus, urethra and vagina  keratinized: skin Stratified squamous epi.( 复层扁平上皮 )

12  flexible-the number of layers and shape of cells  distended bladder: 2-3 layers, become flattened.  contracted bladder : 6-7 layers  Distribution: bladder Transitional epi.( 变移上皮 )

13 Epithelial specializations

14 Specialisations of free surface 1) Cell coat ( 细胞衣 ) 2) Microvillus ( 微绒毛 ) 3) Cilium ( 纤毛 )

15  Definition: a thick layer of extracellular glycoprotein  Function: adherence, supporting, protection, exchange of material and recognize Cell coat ( 细胞衣 )

16  delicate finger-liked projections of cell-membrane and cytoplasm protruding from the free surface Microvilli ( 微绒毛 )

17 Structure  0.1um in diameter, with different length.  core: longitudinal microfilament-actin filament fixed on terminal web ( 终末网 )  terminal web: made up of transverse-arranged filament at the apical side of cells

18 Function: increase the surface areas Distribution:  striated border( 纹状缘 ): intestinal epi. cell  brush border ( 刷状缘 ): proximal renal tubule

19  Definition: elongated, mobile projections of cell membrane and cytoplasm protruding from free surface Cilium ( 纤毛 )

20 Structure:  5-10um long, 0.2um in diameter  core: microtubules, 9X2+2  basal body ( 基体 ): centrioles-connected with microtubules Function: swing to produce a forward-moving wave Distribution: epithelial cells of respiratory tract

21 Specializations of the lateral surface --- intercellular connection of adjacent cells:  non-special: the minute space and cadherin( 钙粘蛋白 )- cell adherent molecules  special: junctional structures 1) Tight junction ( 紧密连接 ) 2) Intermediate junction ( 中间连接 ) 3) Desmosome ( 桥粒 ) 4) Gap junction ( 缝隙连接 )

22 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 Tight Junction (zonula occludens, 闭锁小带 )

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24 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 Intermediate Junction (zonula adherens, 黏着小带 )

25 Structure:  plate or spot-shaped  a gap of nm, with low electron- density filaments interdigitate to form intermediate line  attachment plaque: with attached - intermediate filament (10nm) Function: firmly connection Desmosome (macula adherens 黏着斑 )

26 Structure:  the smallest gap of 2-3 nm  connexons ( 连接小体 ) : consist of protein 7~9nm in diameter 6-subunits of proteins- connexin 2nm channel: hydrophilic channel Function: provide a pathway between cells Gap Junction (communicating junction)

27 Junctional Complex ( 连接复合体 )  four types of junctional structures (at least two types) get together.

28 1) Basement membrane ( 基膜 ) 2) Plasma membrane infolding ( 质膜内褶 ) (basal longitudinal striation) 3) Hemidesmosome ( 半桥粒 ) Specialization of basal surface

29  a sheet of membrane btw epi.cells and underlying CT.  HE pink color, hard to see  EM: --lamina lucida ( 透明板 ) --lamina basal ( 基板 ): nm, electron-dense, thread-liked and amorphous ground substance, produced by epi. Cell --reticular lamina ( 网板 ): RT+ground substance, produced by CT Basement Membrane

30 Function:  support, connection, fixation  semi-permeable membrane  induce the movement, proliferation and differentiation of epi.cell

31  infolding of basal cell-membrane, many mitochondria  Function: increase the basal surface areas facilitate the passage of water and ions  Distribution: mainly in proximal and distal renal tubule. Plasma membrane infolding (basal longitudinal striation, 基底纵纹 )

32  Basal,half of desmosome Hemidesmosomes ( 半桥粒 )

33  glandular epi.: epi are specialized for secretion  gland: organs composed mainly of glandular epi. Classification:  exocrine gland ( 外分泌腺 ): through a duct system  endocrine gland ( 内分泌腺 ): directly into blood steam Glandular epi. and gland ( 腺上皮和腺体 )

34  Serous acinus ( 浆液性 )  Mucous acinus ( 黏液性 )  Mixed acinus: serous demilune Structure of exocrine gland

35  simple squamous epi to simple columnar or stratified epi.  carry out the secretions  secrete or absorb water and ions Ducts

36  The End