Gut epithelium cells line our intestines and other digestive organs. The epithelium contains 4 layers that are required for absorbing water, nutrients and minerals from food, the most outer layer must prevent auto digestion (digesting your own tissues) and prevent infectious material passing through lining.
The stomach surface is lined with epithelial cells that have numerous invaginations called gastric pits. The surface epithelial cells, called surface mucous cells, produce an alkaline mucous that protects the surface of the stomach from its acid contents. Below the gastric pits are the gastric glands (red) that secrete hydrochloric acid. Towards the base of the image are chief cells (black) that secrete pepsinogen from which the protease pepsin is derived. Below the chief cells are layers of smooth muscle and the submucosa, with occasional large blood vessels.