Gastrointestinal hormones

The mucous membrane lining the alimentary canal is both exocrine (digestive juices) and endocrine:

• Gastrin: secreted by the stomach wall; carried by blood back to the stomach glands, stimulating further secretion of gastric juice.
• Secretin: secreted by the lining of the small intestine (duodenum); stimulates the pancreas to secrete pancreatic juice (rich in bicarbonate).
• Cholecystokinin (CCK): also from the intestinal lining; stimulates the pancreas to secrete enzymes and makes the gall bladder contract to release bile into the duodenum.