Gastric mucosa belongs to part of the stomach wall, it belongs to the most superficial layer of the mucous membrane layer, the gastric mucosa is mainly rich in glands, there are three kinds of cells composed of the main cell it can secrete pepsinogen in the acidic environment can be transformed into active pepsin, help digest food. There is also a kind of wall cells can secrete hydrochloric acid and endogenous factors, which can help the absorption of vitamin B12, hydrochloric acid is able to protect the acidic environment of the stomach; there is also a kind of mucus cells, which can secrete alkaline mucus, and play the role of neutralization of gastric acid, so that the surface of the gastric mucosa is neutral or alkaline, to protect the gastric mucosa from erosion of gastric acid.