Enterocytes, Epithelial Renewal

• Enterocytes are usually shed after 2-8 days.
• To replace enterocytes. epithelial progenitor cells in the crypts of the small intestine continually divide.
  • New epithelial cells move up towards the surface (i.e. the tip of the villus).
  • As cells move up, they differentiate and lose the ability to divide.
• When epithelial cells are lost (rather than shed), the damage is repaired.
  • Minor loss results in the lateral migration of adjacent cells.
    • Repair within minutes.
  • More major loss results in contraction of the villus, and cells migrate across intercrypt surface.

• Epithelial renewal is in a state of dynamic equilibrium.
  • Enterocyte production in crypts = shedding from villus tip into lumen.
• Disruption of this equilibrium by any disease can cause lesions of the mucosa and villi.
  • E.g. villus atrophy.