Which cells in the stomach secrete hydrochloric acid?

• A. Chief cells
• B. Mucous cells
• C. Parietal cells
• D. G cells

Answer: (C)

Parietal cells, also called oxyntic cells, line the gastric glands in the stomach lining and are the ones that secrete hydrochloric acid. They generate HCl by using a proton pump (H+/K+-ATPase) to move hydrogen ions into the stomach lumen, with chloride ions accompanying to form the acid. This creates the very acidic environment needed to activate pepsinogen into pepsin and to assist in protein digestion, while also helping kill many ingested microbes. Acid secretion is stimulated by signals such as gastrin from G cells, histamine from other secretory cells, and acetylcholine released by nerves, and it is inhibited by regulatory factors like somatostatin. The other gastric cell types have different roles—mucous cells produce protective mucus, chief cells secrete pepsinogen, and G cells release gastrin to promote acid production but do not secrete acid themselves.