Digestive hormones gastrin

Know the action of hormones involved in the digestion and metabolism of food substances insulin, glucagon, secretin, gastrin, and cholecystokinin. Know their chemical and physiologic properties and what controls their blood levels. 

Both the stomach and the small intestine elaborate peptide hormones into the bloodstream, which is crucial in initiating food digestion. The most important hormones of this class are gastrin, secretin, and cholecystokinin. Their structures are displayed in Figure 16.13. 

Gastrin is a hormone released from the stomach that controls the progress of digestion. Early work on the hormone showed that only the four C-terminal amino acids of the peptide were necessary for its physiological activity. 

Gastrin-Producing Cells Secrete gastrin, a hormone that regulates the release of enzymes during digestion... 

Pancreas a vertebrate organ producing a digestive secretion which enters the adjacent duodenum in response to the hormones Secretin (see) and Cholecys-tokinin (see). It also contains about 1 million islets of Langerhans, each with a diameter of ISO un these have a rich blood supply and are innervated with unmyelinated nerve fibers. The islets contain various types of hormone-producing cells, the A cells which produce Glucagon (see), the B cells which make Insulin (see) and the D cells which manufacture Gastrin (see). 

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