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Sunday, May 24, 2009

How is the digestive process controlled?

Hormone Regulators
The major hormones that control the functions of the digestive system are produced and released by cells in the mucosa of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system where they stimulate digestive juices and cause organ movement.
The main hormones that control digestion are gastrin, secretin, and cholecystokinin (CCK):
Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. Gastrin is also necessary for normal cell growth in the lining of the stomach, small intestine, and colon.
Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate. The bicarbonate helps neutralize the acidic stomach contents as they enter the small intestine. Secretin also stimulates the stomach to produce pepsin, an enzyme that digests protein, and stimulates the liver to produce bile.
CCK causes the pancreas to produce the enzymes of pancreatic juice, and causes the gallbladder to empty. It also promotes normal cell growth of the pancreas.
Additional hormones in the digestive system regulate appetite:
Ghrelin is produced in the stomach and upper intestine in the absence of food in the digestive system and stimulates appetite.
Peptide YY is produced in the digestive tract in response to a meal in the system and inhibits appetite.
Both of these hormones work on the brain to help regulate the intake of food for energy. Researchers are studying other hormones that may play a part in inhibiting appetite, including glucagon-like peptide-1 (GPL-1), oxyntomodulin (+ ), and pancreatic polypeptide.

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