Name two protective mechanisms of the stomach against self-digestion.

• A. Thin mucus layer provides all protection
• B. Tight junctions are the primary protective mechanism
• C. A thick mucus layer with bicarbonate and rapid turnover of epithelial cells protect the stomach
• D. The stomach uses no protective strategies

Answer: (C)

Two main defenses keep the stomach from digesting itself: a mucus-bicarbonate barrier and rapid renewal of the lining. The mucus layer is thick and rich in bicarbonate, which sits right at the mucosal surface to neutralize much of the stomach’s acid and pepsin, creating a protective microenvironment. At the same time, the surface epithelium turns over quickly, so any cells that are damaged by acid are shed and replaced rapidly, limiting exposure to injury. Together, these mechanisms form a robust shield against self-digestion. While other features like tight junctions support the barrier, they aren’t the primary protective means, and the idea that no protection exists is incorrect.