The gastric mucosa is the mucous membrane layer that lines the entire stomach. The mucus is secreted by gastric glands, and surface mucous cells in the mucosa to protect the stomach wall from harmful gastric acid, and from digestive enzymes that may start to digest the tissue of the wall. Mucus from the glands is mainly secreted by pyloric glands in the lower region of the stomach, and by a smaller amount in the parietal glands in the body and fundus of the stomach.
The mucosa is studded with millions of gastric pits, which the gastric glands empty into. In humans, it is about one millimetre thick, and its surface is smooth, and soft. It consists of simple secretory columnar epithelium, an underlying supportive layer of loose connective tissue called the lamina propria, and the muscularis mucosae, a thin layer of muscle that separates the mucosa from the underlying submucosa. The gastric mucosa serves as a gastric barrier, reinforced by tight junctions between the epithelial cells.