Why doesn't stomach acid harm the stomach?

The reason why gastric acid does not harm the stomach is primarily due to multiple protective mechanisms of the stomach, which work together to ensure that gastric acid does not damage the stomach during the digestive process. Specifically, these mechanisms include the following aspects:

1. Chemical barrier: The epithelial cells and digestive glands of the gastric mucosa can secrete mucus, which contains bicarbonate. This bicarbonate reacts with gastric acid to produce water and carbon dioxide, thereby reducing the direct aggressive and digestive effects of gastric acid on the stomach. This mucus barrier effectively isolates gastric acid and pepsin, preventing them from damaging the gastric mucosa.

2. Physical barrier: The mucus secreted by the gastric mucosa also has significant viscosity, forming a lubricating layer that reduces mechanical friction caused by coarse food on the stomach. At the same time, this mucus layer prevents direct contact between gastric acid, pepsin, and the gastric mucosa, thus preventing corrosive damage.

3. Rich blood circulation: The gastric mucosa contains a large number of capillaries, resulting in abundant blood circulation in the stomach. This rich blood supply not only provides adequate nutritional support to the stomach but also enhances the gastric mucosa's resistance to erosion by gastric acid.

4. Rapid repair capability: The epithelial cells of the gastric mucosa have a relatively fast regeneration rate. Once injury occurs, as long as the causative factors are promptly removed, the damage can usually be rapidly repaired, thereby reducing further harm from gastric acid to the stomach.