What is the composition of gastric juice? Why does gastric juice not damage the stomach walls?

Gastric juice consists of water and active ingredients: enzymes and hydrochloric acid. Hydrochloric acid creates an aggressive environment necessary for the effective functioning of enzymes. Only in such an acidic environment will enzymes be able to fully work and digest food. This aggressive juice does not dissolve a healthy stomach wall, since there are also protective factors. The stomach lining contains cells that produce mucus. This mucus does not allow the juice and mucous membrane to come into contact. Another protective factor: the constant replacement of epithelial cells of the wall with new ones, they are constantly growing and replacing.