Gastric secretions Essay

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Which substances, other than gastric acid, are secreted by the stomach? Describe their secreted and physiological roles. o Two main tubular glands are present in the stomach mucosa: • Oxyntic/gastric glands • Pyloric glands In addition, mucus-secreting cells line the entire surface of the stomach (surface mucous glands). These secrete large quantities of a very viscid mucus that coats the stomach mucosa with a gel layer of mucus, often more than 1mm thick. These glands provide a major shell of protection for the stomach wall and contribute to lubrication of food transport. The mucus produced by these mucus-secreting cells is alkaline (thus the normal stomach wall is not exposed to the highly acidic and proteolytic stomach secretions directly). o Oxyntic/gastric glands: • Located on the inside surfaces of the body and fundus of the stomach • Constitute the proximal 80% of the stomach • A typical gland is composed of 3 types of cells: mucous neck cells which secrete mainly mucus; peptic/chief cells which secrete large quantities of pepsinogen; parietal/oxyntic cells which secrete hydrochloric acid (gastric acid) and intrinsic factor o Pyloric glands: • Are located in the antral portion of the stomach • Make up the distal 20% of the stomach • Secrete mainly mucus for protection of the pyloric mucosa from gastric acid; also secrete the hormone gastrin and a small amount of pepsinogen o Pepsinogen: • Secreted mainly by peptic cells of the oxyntic glands, but a small amount is also secreted from the mucous cells of the oxyntic glands and from the pyloric glands (function is the same) • Molecular weight = c. 42,500 Da • Is inactive when first secreted into the into the stomach • Is activated to form pepsin: during this process, pepsinogen is split into a 35,000 Da molecule (pepsin) HCl creates an acidic environment which allows pepsinogen to

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