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Chapter 2 Epithelial tissue

Chapter 2 Epithelial tissue. 1.General feature: 1) contain more cells and less extracellular ground substance 2) Polarisaton : ---free outer surface: face the surface of the body or the lumen of an organ or gland ---basal surface: face underlying connective tissue

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Chapter 2 Epithelial tissue

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  1. Chapter 2Epithelial tissue

  2. 1.General feature: 1) contain more cells and less extracellular ground substance 2) Polarisaton: ---free outer surface: face the surface of the body or the lumen of an organ or gland ---basal surface: face underlying connective tissue 3)  Avascularity, but innervation: ---no blood vessels ---rich in nerve terminals 4) Cellular Layer + Basement Membrane 5) Functions: protection secretion absorption 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. * Myoepithelial cell

  4. 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. Cell shape

  6. Cell Layers Simple Stratified

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

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

  9. Vascular endothelium

  10. Mesothelium on abdominal cavity

  11. 2)simple cuboidal epi.: ---structural feature: • one layer of cells, with same height and width , hexagonal in shape. • spherical centrally-located nucleus

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

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

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

  15. four types of cells 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.

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

  17. 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

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

  19. 6)transitional epithelium: • Flexible qualities ---ncluding the number of layers and shape of cells

  20. ---distribution: bladder

  21. in the contractedbladder in the distendedbladder

  22. 4. Epithelial specializations • Sides of cells: • --- Apical (free) • --- Basal • --- Lateral

  23. 1)Specializations of free surface

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

  25. ---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

  26. ---function: increase the surface areas, thus aid in the processes of secretion and absorption. ---distribution: /striated border: intestinal epi. cell /brush border: proximal renal tubule Striated border

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

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

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

  30. ---function: beat in a rhythmical manner and produce a forward-moving wave ---distribution: epithelial cells of respiratory tract respiratory tract

  31. 2)specializations of the lateral surface

  32. ---intercellular connection of adjacent cells: • non-special manner: the minute space and adherent molecules (glycoproteins, proteoglycans, cadherin) • Special manner: junctional structures

  33. ①Tight 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. ③desmosome (macula adherens): ---structure: • plate or spot-shaped • a gap of 20-30 nm, with low electron-density filaments interdigitate • attachment plaque • Many tonofilaments are inserted into attachment plaque, each filament make a hairpin loop and then passes back into the cytoplasm • ---function: firmly connection

  36. ④gap 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: electron-lucid central channel ---function: provide a ions and small molecules pathway between cells

  37. connexons

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

  39. 3)specialization of basal surface

  40. ①basement membrane: ---definition: a sheet of membrane-liked amorphous material interposed between epithelium cells and underlying CT. ---structure: • HE: pink colour, hard to see • PAS +

  41. EM: two layers --basal lamina: 20-300 nm, electron-dense, thread-liked and amorphous ground substance, produced by epithelium Cell --reticular lamina: RT+ground substance, produced by CT

  42. ---function: • support, connection, fixation • semi-permeable membrane • induce the movement, proliferation and differentiation of epithelium cell

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

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

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

  46. SUMMARY 1：

  47. SUMMARY 2：

  48. 5. Glandular epithelium and gland (study yourself ) • glandular epithelium: are specialized for secretion • gland: organs composed mainly of glandular epiithelium

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

  50. Simple gland compound alveolar gland compound tubulo-alveolar gland 2) structure of exocrine gland:

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