Tasks of the stomach mucosa
The surface of the stomach mucosa is greatly enlarged by numerous crypts (stomach glands). Within these glands there are different types of cells which together produce the gastric juice. The so-called main cells are located at the base of the glands.
These are basophilic cells with apical secretion granules containing pepsinogen, a protease for protein digestion. Besides pepsinogen, main cells also secrete gastric lipase for the cleavage of fats. Parietal cells are located in the centre of the gland and are the only cells that can produce hydrochloric acid.
In addition, parietal cells produce intrinsic factor, a transport protein required for the absorption of vitamin B12 in the terminal ileum. Secondary cells are located in the area of the gland neck and secrete bicarbonate and mucin. Neuroendocrine cells (H, D and G cells) are distributed throughout the stomach mucosa and produce neurotransmitters and gastrointestinal hormones to control digestion. In addition to the stomach glands, the mucosa consists of the actual surface epithelial cells, which serve to protect the mucosa from aggressive gastric acid by releasing mucus and bicarbonate for neutralization.