Current concepts of gastroduodenal mucosal protection.
Mucosal protection against luminal acid and pepsin and recovery from acute damage in the upper gastrointestinal tract depends upon a number of interrelated mechanisms. The thin adherent mucus gel layer protects against shear and luminal pepsin and provides a mixing barrier for surface neutralization of H+ by HCO3- secreted from the underlying epithelia. Gastric HCO3- transport amounts to 2-10% of maximum H+ rate and involves a Cl- exchange mechanism. The rate of duodenal HCO3- transport is some 5-fold greater and both Cl- exchange and transcellular secretion of HCO3- occur. Blood flow ensures adequate oxygenation, provides a pool of HCO3- and maintains mucosal acid-base balance. Gastroduodenal mucosa has a high proliferative rate and in the stomach, the process of continual cell replacement is augmented by restitution of epithelial integrity following acute damage.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001692:Biological Transport; D002455:Cell Division; D004386:Duodenum / Q000502:physiology; D004847:Epithelial Cells; D005744:Gastric Acid / Q000378:metabolism; D005753:Gastric Mucosa / Q000098:blood supply / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000098:blood supply / Q000378:metabolism / Q000502:physiology*; D007474:Ion Exchange; D008833:Microcirculation / Q000502:physiology; D009093:Mucus / Q000502:physiology; D010434:Pepsin A / Q000378:metabolism
D001639:Bicarbonates; D010434:Pepsin A