Hormonal Control of Digestive Secretions:
Nervous and Endocrine systems coordinated the activities of the gastrointestinal (GI) tract. The very sight and smell of food send signals to the nervous system which stimulate the secretions from salivary and gastric glands. The release of secretions from the digestive glands is controlled by hormones produced by epithelium of certain regions of alimentary canal. These hormones are carried by blood to the digestive glands which then release their secretions. Following hormones regulate the digestive secretions-
- Gastrin- It is secreted by gastrin cells in the pyloric region of the stomach. It stimulates the gastric glands to secrete and release the gastric juice. It also stimulates gastric mobility.
- Secretin- It is produced by S-cells of the mucosa of duodenum and jejunum. It stimulates the release of sodium bicarbonate fluid from the pancreas and liver. It also increases bile secretion. It also inhibits the secretion of Gastrin.
- Enterogastrine- The hormone is produced by the duodenum. It is an uncharacterized hormone that reduces the digestive activity of the stomach. It is believed to be formed when there is excess fat in the food.
- Duocrinin- It is produced by the duodenum in response to the entry of chyme. Duocrinin stimulates Brunner’s glands for producing mucus and bicarbonate in order to protect the duodenal lining.
- Gastric Inhibitory Peptide- It is produced in the upper part of the intestine in response to the presence of excess fat and protein in the chyme. It decreases the motor activity of the stomach. It gives enough time for intestinal juices to act on fats and proteins.
- Enterocrinin- It is produced by the duodenum. The hormone stimulates crypts of lieberkuhn to release the enzymes in the intestinal juice.
- Cholecystokinin- The hormone is formed by I-cells present in the lining of the duodenum and upper part of the jejunum. It stimulates contraction of the gall bladder, relaxes the sphincter of Oddi and secretion of bile from liver lobes.
- Villikinin- It is produced by mucosa of small intestine. It stimulates movements of villi for increased absorption of food.
- Motilin- It is a polypeptide hormone that is secreted in the intestine in response to the presence of acid and fat in the duodenum. It brings about motility of the intestinal tract.