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Answer: a, c
The endocrine functions of the small intestine are diverse with an ever increasing number of hormones, peptides, neurotransmitters, and paracrine substances identified. Cholecystokinin (CCK) is produced by cells located primarily in the mucosa of the duodenum and jejunum and released in response to luminal fats and proteins. After CCK release from the duodenum and jejunum, the gallbladder contracts and the sphincter of Oddi relaxes, emptying bile into the duodenum. Secretin is found in the S cells of the duodenum and jejunum. Secretin, a true hormone, is released in response to acid in the duodenum when luminal pH falls below 4.5. Intraduodenal secretion of pancreatic bicarbonate neutralizes duodenal pH and results in diminished release of secretin. CCK acts in a synergistic fashion with secretin to stimulate pancreatic exocrine function. Motilin is a 22-amino acid peptide localized in the enterochromaffin cells of the mucosa of the upper small intestine. Motilin likely has a physiologic role in the regulation of the migrating motor complex (MMC). Motilin is released during the fasting state, and increased levels correspond with the onset of the MMC. Neurotensin is a 13-amino acid neurotransmitter found in the central nervous system and in the gut. Specific endocrine cells that contain neurotensin are found in the ileal mucosa with smaller quantities found in the jejunum, stomach, duodenum, and colonic mucosa. Neurotensin is released by a mixed meal and fats, with carbohydrates and protein releasing much smaller increments. It has been proposed that neurotensin has a physiologic role in fat-initiated changes in gastric acid secretion, gastric emptying, pancreatic secretion, and intestinal motility.
Category: Gastroenterology MCQs
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