5 epithelium sp

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5 epithelium sp

  1. 1. EPITHELIUM DR. SWATI PATIL
  2. 2. INTRODUCTIONEpi= upon; Thelia= nippleDEVELOPMENT Ectoderm- skin, mouth, nose and anal canal. Endoderm- GIT, glands, resp tract Mesoderm-body cavities (Mesothelium), endothelium.
  3. 3. Function of Epithelial Tissue• Protection• Absorption• Filtration• Secretion
  4. 4. Characteristics of Epithelial Tissue• Form continuous sheets (fit like tiles)
  5. 5. • Apical Surface – All epithelial cells have a top surface that borders an open space (lumen)
  6. 6. • Basement Membrane – anchors epithelial cells to underlying connective tissue
  7. 7. BASEMENT MEMBRANE- visible under LM- PAS +- comprises of basal lamina& reticular lamina
  8. 8.  BASAL LAMINA - visible in EM - 20-100 nm thick - consists of dense and clear layers - composed of macromolecules 1. Laminin 2. Type IV collagen 3. Entactin (Nidogen) 4. Proteoglycans
  9. 9. • Avascularity – Lacks blood vessels – Nourished by connective tissue• Regenerate & repair quickly
  10. 10. Classification of Epithelial Tissue
  11. 11. Classification of Epithelial Tissue - Criteria • Cell Shape – Squamous – flattened – Cuboidal - cubes – Columnar - columns
  12. 12. • Cell Layers – Simple (one layer) – Stratified (many layers) • Named after type of cell at apical surface
  13. 13. Simple Squamous Epithelium• Structure – Single Layer of flattened cells• Function – Absorption, and filtration – Not effective protection – single layer of cells.• Location – Walls of capillaries, air sacs in lungs – Form serous membranes in body cavity
  14. 14. Simple Cuboidal Epithelium• Structure – Single layer of cube shaped cells• Function – Secretion and transportation in glands, filtration in kidneys• Location – Glands and ducts (pancreas & salivary), kidney tubules, covers ovaries
  15. 15. Simple Columnar Epithelium• Structure – Elongated layer of cells with nuclei at same level• Function – Absorption, Protection & Secretion – When open to body cavities – called mucous membranes
  16. 16. Simple Columnar Epithelium• Special Features – Microvilli, bumpy extension of apical surface, increase surface area and absorption rate. – Goblet cells, single cell glands, produce protective mucus.• Location – Linings of entire digestive tract
  17. 17. Features of Apical Surface of Epithelium
  18. 18. Microvilli Finger-like extensions of plasma membrane of apical epithelial cell Increase surface area for absorption Temporary or permanent 1 µm : height, 0.8 µm : width BRUSH/STRIATED BORDER: seen in LM Terminal web : supports microvilli composed of actin filaments w/ fimbrin & villin (eg.) in small intestine
  19. 19. Features of Apical Surface of Epithelium Cilia: (eg.) respiratory tubes  Whip-like, motile extensions  Moves mucus, etc. over epithelial surface 1-way  5-10 µm : length  0.2 µm : diameter * Flagella: (eg.) spermatozoa  Extra long cilia  Moves cell
  20. 20.  Stereocilia (eg.) epididymis & ductus deferens  Longer but non motile, compared to microvilli  Branched
  21. 21. Pseudostratified Epithelium• Structure – Irregularly shaped cells with nuclei at different levels – appear stratified, but aren’t. – All cells reach basement membrane• Function – Absorption and Secretion – Goblet cells produce mucus – Cilia (larger than microvilli) sweep mucus• Location – Respiratory Linings & Reproductive tract
  22. 22. Myoepithelial cells
  23. 23. Stratified Squamous Epithelium• Structure Many layers (usually cubodial/columnar at bottom and squamous at top)Function – Protection – Keratin (protein) accumulates in older cells near the surface • waterproofs and toughens skin. Nonkeratinised• Location Keratinised
  24. 24. Stratified squmous keratinised
  25. 25. Stratified squamous non-keratinised
  26. 26. Stratified cuboidal epithelium
  27. 27. Stratified columnar epithelium
  28. 28. Transitional Epithelium• Structure – Many layers – Very specialized • cells at base are cuboidal or columnar, at surface will vary. – Change between stratified & simple as tissue is stretched out.• Function – Allows stretching (change size)• Location – Urinary bladder, ureters & urethra
  29. 29. GLANDS• One or more cells that make and secrete a product.• Secretion = protein in aqueous solution: hormones, acids, oils.• Endocrine glands – No duct, release secretion into blood vessels – Often hormones – Thyroid, adrenal and pituitary glands• Exocrine glands – Contain ducts, empty onto epithelial surface – Sweat, Oil glands, Salivary glands, Mammary glands.
  30. 30. Modes of Secretion• (How the gland’s product is released)• Merocrine - secretory products are released by exocytosis – Ex: Sweat glands and salivary glands• Apocrine -apical part is shed off to discharge – secretion - Ex:mammary glands
  31. 31. Modes of Secretion• Holocrine – Entire cell disintegrates while discharging its secretion – Sebaceous (oil glands on the face) only example
  32. 32. Classification of Exocrine glandsBranching  Simple – single, unbranched duct  Compound – branched.
  33. 33. • Shape: – tubular or alveolar – Tubular – shaped like a tube – Alveolar – shaped like flasks or sacs – Tubuloalveolar – has both tubes and sacs in gland
  34. 34. Cell Junctions & Cell-Cell Adhesion
  35. 35. Classification of cell contacts• Unspecialised contacts -cell adhesion molecule -intermediate protein
  36. 36. Actin cytoskeleton dependent cell-cell and cell-ECM adhesions Cell-cell adherence junctions 1. Calcium-dependent  Cadherins  Selectins  Integrins 2. Calcium-independent  Neural cell adhesion molecule  Intercellular adhesion molecule
  37. 37. • Specialized contacts -Anchoring junctions 1.Adhesive spots or desmosomes or macula adherens 2.Adhesive belts or zona adherens 3.Adhesive strips or fascia adherens - Occluding junction or zonula occludens or tight junction -Communicating junctions or gap junctions
  38. 38. Desmosomes
  39. 39. Zonula adherens
  40. 40. Fascia adherens
  41. 41. Desmosomes &hemidesmosomes
  42. 42. Focal adhesion plaques
  43. 43. Tight Junctions
  44. 44. Types of Cell Junctions
  45. 45. Summary of cell junctions
  46. 46. Thank you

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