In: Anatomy and Physiology
Explain the regulation of gastric secretions.
Gastric acid is hydrochloric acid which is secreted by parietal cells. There are three key stimulants of gastric acid secretion. They include histamine, gastrin and acetylcholine.
Nearly 20% of acid secretion occurs during cephalic phase of digestion of food, the signals of which are obtained from medulla oblongata. 50-60% of total gastric acid secretion is observed in gastric phase.
The parietal cells are associated with acid secretion. During resting condition, the parietal cell is filled with vesicles. When acid secretion initiates, there is a morphological change in vesicle. Activation of the parietal cell upsurges cytoplasmic calcium, tracked by activation of a cAMP-dependent kinase cascade causing movement of the proton pump to the apical surface of the cell. The H+ /K-ATPase (proton pump) pumps H+ ions by exchanging K+. The mitochondria of parietal cell supply ATP to supply sufficient energy for the membrane embedded proton pump. Inhibition of of acid secretion is related to the re-internalization of the H+ /K-ATPase pumps. s. Cl- is extruded down the electrochemical gradient via channels by a cAMP pump in the apical membrane which drives the Cl- / HCO3- exchange. The acid secreted by parietal cells has pH of 0.8