Epithelia

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Epithelia

• Part Deux

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Epithelium
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Pseudostratified Columnar Epithelium

• Crowded columnar 2 cell shapes with nuclei in
  different positions (levels), gives false
  stratified appearance
• all cells touch basement membrane
• Three predictable features
• a) goblet cells
• b) 2 nuclei layers
• c) cilia
• Tissue prevents stabilizing mucous
• Common in ventilatory and reproductive ducts.
• Non-ciliated in large gland excretory ducts.
• Functions in providing moist atmosphere without
  stabilizing secretions.

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Stratified Squamous Epithelium

• Cells not all squamous shaped - basal cells are
  cuboidal, become flattened as they move to the
  surface.
• Covers the body surface and openings.
• True stratified tissue only basal layer
  (cuboidal cells) touches the basement membrane.
• Since surface cells are squamous, Squamous
  epithelium.
• All cells tightly adherent - ground substance and
  
• desmosomes hold cells together. Basement
• membrane (loose CT) anchors tissue.

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Stratified Squamous Epithelium

• Two functional-anatomical expressions
• a) cornified stratified squamous epithelium
• Outer 5-20 cell layers die and are filled with
  the protein Keratin to protect the surface of
  the body and prevent dehydration.
• - keratinization is a protective physiological
  response Metaplasia.
• b) non-cornified stratified squamous epithelium
• all cell layers are alive tissue is internal
  in
• the body in a favorable moist environment.
  E.g. oral cavity, vagina, esophagus, anal
  canal.

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Keratin in the animal world
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• Non-keratinized
• Moist Epithelium
• Living Cells at Apical Surface

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• The distinguishing feature of stratified squamous
  epithelium is dermal papillations.
• - only the basal cell layer divides and cells
  constantly move from basally to the free
  surface.
• Functions in protection and secretion.

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Stratified Cuboidal Epithelium

• Rare
• Enamel organ of teeth, ovarian follicle, kidney.
• Functions as specialized or intermediate
  epithelium.

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Stratified Columnar Epithelium

• Not common soft palate, excretory ducts of
  salivary glands.
• Functions as transient or intermediate epithelium.

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Transitional Epithelium

• Modified, non-cornified stratified squamous
  and/or stratified cuboidal/columnar.
• 4-6 layers of cells. Basal layer cuboidal, inner
  layers of balloon to pear shaped cells outer
  layer of squamous cap cells.
• Features of the tissue.
• - capable of great stretching.
• - line ureters and urinary bladder.

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Transitional Epithelium

• Two anatomical expressions
• a) classical as above urinary bladder.
• b) extremely tall stratified
  columnar/cuboidal with cap cells ureter.

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