Video - Stomach histology

The stomach is an expanded portion of the gastrointestinal tract or GI tract that partially digests food by breaking it down mechanically and chemically to form a pulpy acidic fluid called chyme. The stomach has four main regions: the cardia, fundus, body, and pylorus. The wall of the stomach is composed of four layers: the mucosa, submucosa, muscularis, and serosa. The mucosa is the innermost layer and contains several important structures for digestion, including gastric pits, gastric glands, and specialized cells.

Gastric pits are invaginations in the mucosa that lead to gastric glands, which secrete gastric juice. The gastric glands are composed of several cell types, including parietal cells, chief cells, and mucous cells. Parietal cells secrete hydrochloric acid (HCl) and intrinsic factor, which is necessary for the absorption of vitamin B12. Chief cells secrete pepsinogen, which is the inactive form of pepsin, an enzyme that breaks down proteins.

Mucous cells secrete mucus, which protects the stomach lining from the acidic environment of the stomach. The muscularis layer is responsible for the movement of the stomach and is composed of three layers of smooth muscle. The submucosa layer contains blood vessels, nerves, and lymphatic tissue. The serosa layer is the outermost layer of the stomach and provides a protective covering.