The Hormones of the Digestive System
From MyMCAT
Contents |
Introduction
Throughout the body, various hormones play critical roles in regulating digestion. The linear process of events that takes place during digestion must be both accurate and efficient, and the hormones of the digestive system do just this.
Secretin
Secreted by the cells of the duodenum in response to a lowered pH, secretin stimulates the release of bicarbonate (from the pancreas/gallbladder and inhibits stomach motility (release into the small intestine). Both of these effects are in an attempt to maintain high pH in the small intestine and counter act the lowering pH caused by chyme from the stomach entering the intestines.
Cholecystokinin (CCK)
Cholecystokinin, or CCK, is a peptide hormone released by the duodenum that stimulates the digestion of fat and protein. It acts on the pancreas to stimulate the secretion of digestive enzymes and on the stomach to inhibit the release of gastric acid. (This inhibitory effect is similar to the response of secretin as both are used to prevent a rapid drop in pH due to stomach contents being released into the intestines.)
Gastrin
Secreted by both cells in the duodenum and the stomach, gastrin is used to stimulate secretion of gastric acid by the parietal cells of the stomach.
Summary
In summary, both secretin and CCK are used to slow down the release of chyme from the stomach to allow the duodenum time to digest and maintain high pH. CCK is also used to stimulate the release of necessary digestive enzymes. Gastrin however, is used to stimulate digestion in the stomach.
