Which cells secrete hydrochloric acid in the stomach?

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

Answer: (D)

Acid secretion in the stomach is carried out by parietal cells in the gastric glands of the stomach’s body and fundus. These cells house the proton pump H+/K+-ATPase on their apical surface, which actively pumps hydrogen ions into the lumen in exchange for potassium. The hydrogen ions combine with chloride ions, which enter the cell and then move into the lumen to form hydrochloric acid. This creates the highly acidic environment necessary to activate pepsinogen into pepsin and to aid digestion, and parietal cells also provide intrinsic factor for vitamin B12 absorption. Parietal cells are stimulated by acetylcholine, gastrin, and histamine. The other cell types mentioned—G cells that secrete gastrin, mucous cells that secrete mucus, and chief cells that secrete pepsinogen—do not secrete acid themselves.