No one has provided the actual answer yet. Here it is- The gastroduodenal epithelium (stomach surface) is covered by a sticky mucus layer into which bicarbonat

No one has provided the actual answer yet. Here it is- The gastroduodenal epithelium (stomach surface) is covered by a sticky mucus layer into which bicarbonate is secreted by surface epithelial cells. This bicarbonate-mucus layer creates a pH gradient with a near-neutral pH at the epithelial surfaces in stomach and duodenum, providing the first line of mucosal protection against luminal gastric acid. We only learned this in the last 20 years so it’s relatively new science Edit: either I misread the question or it was edited