Gastric Mucosal Barrier & Peptic Ulcer Formation

A 3D reaction-diffusion model of the stomach's own line of defense: a mucus-bicarbonate gel that separates epithelial cells from acid strong enough to digest them. Layer by layer, hydrogen ions diffusing down from the lumen meet bicarbonate diffusing up from the epithelium and are neutralised in transit — until the barrier itself is degraded by pepsin, NSAIDs, or a colonizing population of Helicobacter pylori. Push acid secretion, colonization density, or NSAID exposure high enough, or defensive secretion too low, and the barrier thins to the point where acid reaches living tissue directly, visibly eroding a crater into the epithelium — a peptic ulcer forming in real time from the same balance of forces gastroenterologists reason about at the bedside.