By Dr. Sachin Many times we fail to understand how parietal cells create hydrochloric acid in the stomach which assists in digestion. Let’s understand the procedure today. Parietal cells are nothing but epithelial cells that secretes gastric acid. (HCL) They are also known as oxyntic or delomorphous cells and located in the fundus of a stomach wall. These epithelial cells form a network of huge folds within stomach which is called as canaliculi. H+/K+ ATPase (Hydrogen – Potassium ATPase) enzyme is a speciality of these parietal cells and this enzyme helps to generate HCL acid. Synthesis of HCL acid – 1. Carbon Dioxide (CO2) diffuses into parietal cells from the blood stream. 2. Enzyme Carbonic Anhydrase from parietal cells catalyses a reaction between water (H2O) molecule and CO2 to form Carbonic Acid i.e. H2CO3. 3. This carbonic acid further dissociates into Carbonic Ion (HCO3) and Hydrogen Ion (H+). 4. Bicarbonate Ion transported back to the blood stream & while doing so ‘Ion Exchange Pump’ within the plasma membrane of cell exchanges CL– with HCO3–. So CL ion enters the cell. 5. H+ ion then ACTIVELY transported out within the duct of a gastric gland with the help of ‘Ion Exchange Pump’ and K+ ion enters into the parietal cell. At the same time, CL ion diffuses into the duct of gastric gland and forms HCL by connecting with a hydrogen ion. For further understanding please watch this video which will make things more simple and easy to understand.