L2.5: Stratified Epithelia

• • 2 layers of cuboidal cells
  • Functions in protection


  Stratified Cuboidal Epithelium
• • Surface cells are columnar.
  • Cells underneath vary in size and shape.
  • Also functions in protection.


  Stratified Columnar Epithelium
• 2 types of Stratified Squamous Epithelium

  • Keratinized
  • Non-keratinized
• characterized by a presence of keratin. Dry. (example: skin)


  Keratinized
• absence of keratin. Moist. (example: esophagus)


  non-keratinized
• Definition

  • Most common stratified epithelium.
  • Named for cells present at the free (apical) surface, which are flattened.
  • Functions as a protective covering where friction is common.
  • Consist of many cell layers
  • “Skin is keratinized that’s why it’s dry while the esophagus is non-keratinized making it moist.”

  Stratified Squamous Epithelium
• Location (receives friction)

  • Skin (outer portion)
  • Mouth
  • Esophagus



  Stratified Squamous Epithelium
• Definition

  • Highly modified, stratified squamous epithelium that forms the lining of only a few organs.
  • Switching of the shape of the cell.
  • Uterus is not a transitional epithelium because this type of epithelium is only present to excretory organs, just like urinary bladder.
  • Functions in stretching, to change shape, and to return to normal shape.


  transitional epithelium
• Location

  • Lining of the urinary bladder.


  transitional epithelium
• Function

  • stretching
  • Ability to return to normal shape


  transitional epithelium
• Definition

  • Also, Pseudostratified Ciliated Columnar
  • Ciliated Types – Secretes
  • Singled layer with cells that have varying heights (some are shorter) thus giving a false or pseudo impression of stratification.


  Pseudostratified Columnar Epithelium
• Location

  • Most of the respiratory tract lining – mainly the ciliated type that acts as a “sticky trap” catching dust and expelling/propelling unwanted materials like mucus upward.


  Pseudostratified Columnar Epithelium
• Function

  • absorption
  • secretion



  Pseudostratified Columnar Epithelium