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Gastric mucosal barrier
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The stomach holds gastric juice so acidic that it is corrosive, and its enzymes break down protein so well that they could digest the stomach itself. What keeps that from happening is the gastric mucosal barrier.
The barrier has several parts working together. First, the stomach wall is covered by a thick layer of mucus loaded with bicarbonate: the mucus acts as a physical shield and the bicarbonate neutralizes the acid, the way something alkaline cancels out something acidic. Second, the cells of the lining are joined to one another by tight junctions, seals that do not let gastric juice slip through to the tissues underneath. And third, stem cells quickly replace damaged cells as they are shed, so the lining is rebuilding itself all the time.
In brief
The stomach lining is exposed to the highly corrosive acidity of gastric juice, whose enzymes could digest the stomach itself; what prevents that is the gastric mucosal barrier.
That barrier has several parts: a thick layer of bicarbonate-rich mucus that acts as a physical barrier and neutralizes acid, tight junctions between the epithelial cells that keep gastric juice from reaching the tissues underneath, and stem cells that quickly replace damaged cells.
Sources (1)
- OpenStax, Rice UniversityAnatomy and Physiology 2e, 23.4 The Stomach
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