Name and describe the functions of three major hormones involved in digestion and absorption. Include a discussion of the feedback mechanisms that regulate hormone secretion

Answer 1

Food entering the stomach stimulates cells in the stomach walls to release the hormone gastrin. Gastrin, in turn, stimulates the stomach glands to secrete the components of hydrochloric acid. When a pH of 1.5 is reached, the acid itself turns off the gastrin-producing cells. The presence of chyme stimulates the cells of the duodenal wall to release the hormone secretin into the blood. When secretin reaches the pancreas, it stimulates the pancreas to release its bicarbonate-rich juices. When the need has been met, the cells of the duodenal wall are no longer stimulated to release secretin, the hormone no longer flows through the blood, and the pancreas no longer receives the message and stops sending pancreatic juice. Fat in the intestine stimulates cells of the intestinal wall to release the hormone cholecystokinin (CCK). This hormone travels by way of the blood to the gallbladder and stimulates it to contract, which releases bile into the small intestine. CCK also travels to the pancreas and stimulates it to secrete its juices, which releases bicarbonate and enzymes into the small intestine. Once the fat in the intestine is emulsified and enzymes have begun to work on it, the fat no longer provokes release of the hormone, and the message to contract is canceled.