So why doesn't it digest your stomach?
The answer is one of biology's greatest engineering achievements.
Specialized cells in the stomach continuously produce hydrochloric acid, creating a highly acidic environment with a pH often between 1 and 2. This acid helps unfold proteins, activates the digestive enzyme pepsin, and destroys many harmful microorganisms that enter with food.
Yet the stomach survives because it never leaves its cells unprotected.
A thick layer of mucus coats the stomach lining, while bicarbonate trapped within that mucus neutralizes acid directly next to the tissue. At the same time, stomach cells are replaced remarkably quickly, repairing microscopic damage before it becomes a problem.
Global Chemical Database