Mechanical and Chemical digestion in stomach

Mechanical and Chemical digestion in stomach:

• as food reaches pylorus, each mixing wave periodically forces about 3ml of chyme into duodenum through the pyloric sphincter - gastric emptying
• parietal cells secrete H+ and Cl- separately into stomach lumen, net effect is secretion of Hcl. Proton pumps powered by H+/K+ ATPases actively transport H+ into the lumen while brnging K+ into the cell. At the same time Cl- and K+ diffuse out into the lumen through Cl- and K+ channels in the apical membrane. 
• The enzyme carbonic anhydrase is plentiful in parietal cells, catalyses formation of carbon acid from water and carbon dioxide - provides a source of H+ for proton pumps and generates bicarbonate ions. As the bicarbonate ions build up in the cytosol, it exits parietal cells in exchange for Cl- via Cl-/HCO3- antiporters in basolateral membrane. HCO3- diffuses into nearby blood…