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Secretin is a peptide hormone produced in the S cells of the duodenum in the Crypts of Lieberkuhn. Its overall effect is to regulate the pH of the duodenal contents via the control of gastric acid secretion and buffering with bicarbonate.
Cause of secretion Secretin is secreted in response to low duodenal pH due to the acidic chyme, which contains hydrochloric acid, entering from the stomach. Function Secretin stimulates the secretion of bicarbonate (base) from the liver, pancreas, and duodenal Brunner's glands in order to buffer the incoming protons of the acidic chyme. It also enhances the effects of cholecystokinin. It is known to promote the normal growth and maintenance of the pancreas. It also reduces acid secretion from the stomach by inhibiting gastrin release from G cells. This helps neutralize the pH of the digestive products entering the duodenum from the stomach, as digestive enzymes from the pancreas (eg, pancreatic amylase and pancreatic lipase) function optimally at neutral pH. Structure Secretin is a peptide hormone, comprised of 27 amino acids, of which 14 amino acids are homologous to the sequence of glucagon. History In 1902, secretin was first identified to cause a physiological effect in the body after being transported via the blood. This type of substance is called a hormone, which secretin was the first substance to be described as one. The term 'hormone' was coined by William Bayliss and Ernest Starling to categorize such chemical messengers. | ||||||||
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