ויסות pH בקיבה

The low pH in the stomach is maintained by the parietal cells that line the stomach lumen.

As food enters the stomach, a combination of neuronal and cellular signals activate the parietal cells.

Upon activation, the tubulovesicles containing hydrogen-potassium ATPase pumps fuse with the apical membrane to form deep folds called canaliculi.

On the basolateral side of the parietal cells, carbon dioxide from the blood diffuses into the parietal cells. It combines with water to form carbonic acid, which is catabolized by the enzyme carbonic anhydrase into bicarbonate and hydrogen ions.

While the hydrogen ions are pumped into the lumen in exchange for potassium ions via the hydrogen-potassium ATPase pumps, the bicarbonate ions are exported to the blood by the chloride-bicarbonate antiporters in exchange for chloride ions.

Both potassium and chloride ions move into the lumen through their respective channels to maintain the intracellular concentration.

In the lumen, the hydrogen and chloride ions combine to form hydrochloric acid, lowering the stomach pH.