Epithelium

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Author:
mnm2186
ID:
29014
Filename:
Epithelium
Updated:
2010-08-05 18:30:59
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Histology
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Description:
Epithelium
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  1. Functions of epithelium
    • Protection
    • Absorption
    • Secretion
    • Sensation
    • Contraction
  2. Characteristics of epithelium
    • Avascular
    • Cells are tightly packed
    • All epithelium have a basal lamina
    • Forms coverings / linings of organs
    • Forms glands
    • Characterized by intercellular junctions or specializations
  3. Protective epithelium are ______ where Absorptive epithelium are _________
    • Stratified
    • Simple (with high surface area)
  4. Components of Basal Lamina
    • Type IV collagen
    • Laminin
    • Fibronectin
    • Heperin Sulfate
  5. Epithelial Cell Apical Specializations
    • Apical Domain:
    • microvilli
    • cilia
    • stereocilia
    • keratin
  6. Epithelial Cell Basal Specializations
    Basal Domain:

    • hemidesmosomes
    • focal adhesions
    • basement membrane
  7. Epithelial Cell Lateral Specializations
    Lateral Domain: (CAM's)

    • Zonula Occludens (tight junction)
    • Zonula Adherens
    • Macula Adherens (desmosomes)
    • Gap Junctions
  8. Type VII Collagen
    Anchoring fibrils of basal lamina
  9. Type III Collagen
    Reticular fibers
  10. Type IV Collagen
    Basal Lamina
  11. Desmosomes
    (Macula Adherens)
    "Spot weld" between epithelial cells

    Associated with cytokeratin intermediate filaments

    abundant in epithelia that are exposed to physical stress
  12. Hemidesmosome
    Attaches cells to basement membrane

    Prominent in epithelia exposed to physical forces
  13. Gap Junctions
    (Nexus Junctions)
    Very close appositions of adjacent cellular membranes

    Characterized by actual open channels (connexons) between cells.

    Allow for rapid cell-to-cell communication (small molecules)

    Common in cardiac m. and sometimes in nervous tissue
  14. Terminal Bar
    Band surrounding apical end of cell

    Barrier to passage of material between cells

    • Formed by:
    • 1. Zonula Occludens (tight junction)
    • 2. Zonula Adherens
    • 3. Macula Adherens (desmosome)
  15. Zonula Occludens
    (Tight Junctions)
    Surrounds the cell like a belt or band.

    Tight fusion of adjacent membranes

    Prevents luminal materials from diffusing between adjacent cells

    Membranes are fused into a pentalaminar (five-layered) structure.
  16. Zonula Adherens
    Circles the entire cell.

    Morphological similarities to the desmosome

    Holds adjacent cells together.

    Associated with actin microfilaments
  17. Focal Adhesions
    Basal anchoring junction

    Attaches cytoskeletal actin filaments to B.M.

    Prominent role in migration of ep. cells (wound repair)

    Mechanosensative to changes in ECM
  18. Microvilli
    Specialized for absorption (kidney/small intestine)

    Shorter than cilia

    Core of actin microfilaments

    Anchored to terminal web (microfilaments & intermediate filaments)
  19. Cilia
    Function is movement (respiratory tract)

    Move together due to gap junctions

    Organized cytoskeleton - nine doublets and central pair of microtubules

    Microtubules anchored to basal bodies
  20. Stereocilia
    Sensory structure

    Found in epididymis and inner ear
  21. Simple Squamous Epithelium
    • Vascular system (endothelium)
    • Body cavities (mesothelium)
    • Bowman's Capsule (parietal layer - kidney)
    • Respiratory spaces (lung)
    • Endocardium

    Exchange / Barrier (esp. CNS) / Lubrication
  22. Simple Cuboidal Epithelium
    • Ducts / tubules of the kidneys
    • Small ducts of exocrine glands
    • Surface of ovaries (germinal epithelium)
    • Thyroid follicles

    Absorption / Secretion / Barrier / Conduit
  23. Simple Columnar Epithelium
    • GI Tract!!!
    • (small intestine, colon, stomach lining, gastric glands, gall bladder)

    Absorption / Secretion
  24. Stratified Squamous Non-Keratinized Epithelium
    • Esophagus
    • Vagina
    • Oral cavity
    • Nasal cavity

    Protection
  25. Stratified Squamous Keratinized Epithelium
    Skin (epidermis)

    Protection / Water proof
  26. Pseudostratified Epithelium
    (Ciliated vs. Stereociliated)
    • Cilia
    • Trachea & Bronchal tree

    • Stereocilia
    • Male reproductive tract (epididymis / ductus deferens)
  27. Transitional Epithelium
    Urothelium!

    • Renal calyces
    • Ureters
    • Bladder
    • Urethra
  28. Types of Glands
    • Endocrine
    • Exocrine
    • - holocrine
    • - apocrine
    • - merocrine (eccrine)
  29. Classification of multicellular glands
  30. Where are unicellular glands in the GI are first found?
    GI Goblet cells in the duodenum
  31. What are crypts of Lieberkühn?
    Simple tubular glands found in the colon
  32. What are the eccrine sweat glands of the skin? What is special about the ducts?
    Simple coiled tubular glands. Ducts are stratified cuboidal epithelium
  33. Where are compound acinar glands found?
    • Mucous secreting glands of the larynx
    • Exocrine pancreas

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