* Chief cells: These cells produce pepsinogen, an inactive precursor to pepsin. Pepsin is a protein-digesting enzyme that breaks down proteins into smaller peptides.

* Parietal cells: These cells produce hydrochloric acid (HCl), which activates pepsinogen into pepsin, and also helps to:

* Kill bacteria in the stomach.

* Denature proteins.

* Break down food and make it more digestible.

In addition to these two main types of cells, the stomach also contains mucus-secreting cells which produce mucus to protect the stomach lining from the corrosive effects of HCl and pepsin.