Secretin

Secretin is a peptide hormone released by cells in the small intestine when acidic stomach contents enter the duodenum. It stimulates bicarbonate-rich fluid secretion, especially from the pancreas, to neutralize acid.

S cells: Enteroendocrine cells concentrated in the duodenum that release secretin in response to acidic luminal contents. They detect duodenal acidity and release secretin into the bloodstream.
Enteroendocrine cell: A hormone-secreting cell in the gastrointestinal epithelium that senses nutrients or other signals in the gut. Secretin is one product of specialized enteroendocrine cells in the intestinal lining.
William Bayliss: A British physiologist who studied digestive processes and helped establish chemical signaling between organs. Bayliss helped demonstrate that intestinal extracts could stimulate pancreatic secretion.
Secretin stimulation test: A diagnostic procedure that administers secretin and measures pancreatic or biliary fluid responses. The test uses secretin to assess pancreatic exocrine function and investigate selected digestive disorders.
Duodenum: The first section of the small intestine, receiving stomach contents and mixing them with bile and pancreatic secretions. Its acidic contents provide the principal stimulus for secretin release.
Peptide hormone: A signaling molecule made of amino acids that acts by binding cell-surface receptors. Secretin’s peptide structure and receptor-mediated action place it in this hormone family.
Ernest Starling: A British physiologist whose work shaped the study of circulation, kidney function, and hormonal signaling. Starling named secretin and introduced the term “hormone” in describing its action.
Pancreatic exocrine insufficiency: A condition in which the pancreas fails to deliver enough digestive enzymes to the small intestine. Secretin-based testing can help evaluate pancreatic function in suspected insufficiency.
Pancreatic bicarbonate secretion: The release of bicarbonate-rich fluid from pancreatic ducts into the duodenum. This is secretin’s central digestive action, neutralizing acid entering from the stomach.
Pancreas: An abdominal organ with endocrine functions and exocrine secretions that deliver digestive enzymes and bicarbonate to the intestine. Its exocrine ducts are a major target of secretin.

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Bodily secretionsBroader topic: Secretin shows how a digestive signal can trigger a specific glandular fluid.