The epithelial cells that make up the stomach lining are replaced by the body every five days. Stomach lining cells have a quick turnover relative to other types of cells because they are exposed to strong acids in the stomach.
The body is constantly generating new cells to replace older, damaged cells. Types of tissue that suffer more wear and tear need to be replaced more often. Stomach lining cells endure the harshest conditions in the body, being in constant contact with hydrochloric acid; they have a very short life cycle. Other highly stressed cells are replaced within a few weeks' time, whereas some, such as bone cells, take years to regenerate.