Which cells secrete hydrochloric acid and intrinsic factor, and what stimulates them?

• A. Parietal (oxyntic) cells; stimulated by gastrin, histamine, and acetylcholine
• B. Chief cells; stimulated by secretin
• C. G cells; stimulated by cholecystokinin
• D. Mucous cells; stimulated by prostaglandins

Answer: (A)

Parietal (oxyntic) cells are the ones that make both hydrochloric acid and intrinsic factor. These cells line the gastric glands in the stomach’s fundus and body, using a proton pump to secrete H+ into the lumen (forming HCl) and releasing intrinsic factor needed for vitamin B12 absorption in the ileum. Their activity is boosted by three key stimulators: gastrin from G cells, histamine released by nearby enterochromaffin-like cells, and acetylcholine from vagal nerve endings. Gastrin directly stimulates parietal cells and also promotes histamine release, while histamine acts on H2 receptors to further increase acid secretion; acetylcholine provides a direct, rapid boost via muscarinic receptors. The other cell types listed don’t produce both acid and intrinsic factor, so they don’t fit the described function.