Secretin gastric

Secretin Endocrine cells in mucosa of duodenum Acid in duodenum Inhibits gastric emptying and gastric secretion stimulates secretion of bicarbonate from pancreas stimulates secretion of bicarbonate-rich bile from liver... 

An important gastric secretion is the hydrochloric acid that performs a number of functions in the stomach. This stomach acid is neutralized by pancreatic bicarbonate ion in the duodenum. Excess acid in the chyme stimulates chemoreceptors in the duodenum. This receptor stimulation elicits reflex inhibition of gastric motility. Excess acid also causes the release of secretin and gastric inhibitory peptide from the duodenum. These hormones contribute to inhibition of gastric contractions so that the neutralization process may be completed before additional acid arrives in chyme from the stomach. 

The lower the pH, the slower is gastric emptying. Secretin presumably modulates this effect since acid in the duodenum is the prime stimulus for its release, and it has been shown to delay gastric emptying. In addition, neural receptors that respond to acid are present in the duodenum. 

As the acidic stomach contents pass into the small intestine, the low pH triggers secretion of the hormone secretin into the blood. Secretin stimulates the pancreas to secrete bicarbonate into the small intestine to neutralize the gastric HC1, abruptly increasing the pH to about 7. (All pancreatic secretions pass into the small intestine through the pancreatic duct.) The digestion of proteins now continues in the small intestine. Arrival of amino acids in the upper part of the intestine (duodenum) causes release into the blood of the hormone... 

As linear polypeptides, VIP (vasoactive intestinal polypeptide)105), PHI (peptide HI H = N-terminal His, I = C-terminal lie) lo6107) and GIP (gastric inhibitory polypeptide consisting of 43 amino acids)108) are structurally similar to secretin and glucagon. VIP and PHI act as vasodilators, exert hyperglycemic effects, and affect the smooth muscle of the gallbladder. GIP completely blocks gastric secretion. 

Kontureketal. (1976,1984) performed experiments with chronic gastric fistulas in cats as well as in dogs to compare the species-specific activities of vasoactive intestinal peptide and secretin in stimulation of pancreatic secretion. 

There are a variety of peptide hormones acting in the gut the gastrins stimulate gastric acid secretion secretin and somatostatin inhibit the production of gastrins. Cholecystokinin and somatostatin can inhibit gastric acid secretion directly, and the former one causes the gall-bladder to contract and thus force bile into the duodenum. 

Secretin inhibits postprandial gastrin release (thus decreasing gastric acid secretion) and increases pancreatic exocrine secretion (e.g. of bicarbonate). The secretin receptor (like the GLP-1 receptor and vasoactive intestinal peptide (VIP) receptor) acts via Gas and cAMP elevation. A plant agonist for the secretin receptor has been isolated from the Thai anti-ulcer plant Croton sublyratus (plau-loi) (Table 5.8). 

Gastric acid production is regulated by both the autonomic nervous system and several hormones. The parasympathetic nervous system, via the vagus nerve and the hormone gastrin, stimulates the parietal cell to produce gastric acid, acting both directly on parietal cells and indirectly through the stimulation of the secretion of the hormone histamine from ECL cells. Vasoactive intestinal peptides, cholecystokinin and secretin all inhibit acid production. 

Secretin is a 27-residue peptide amide hormone produced by S cells of the duodenum. The primary effect of secretin is stimulating the release of bicarbonate from liver, pancreas, and duodenal tissues to inhibit gastrin-induced gastric acid release. It also enhances the effects of cholecystokinin and promotes normal growth and maintenance of the pancreas. 

Secretin enters the blo<>dstream and travels to the pancreas, where it stimulates the duct cells lo release bicarbonate and large volumes of fluid into the pancreatic duct The duct cells are located in the walls of the pancreatic duct. This duct leads from the acinar cells of the pancreas to the ampulla of Vater. The bicarbonate neutralizes the gastric acid entering the duodenum, providing an environment suitable for the functioning of enzymes and absorptive processes that re<]uire a neutral pH. 

In seven healthy controls, seven patients with duodenal ulcer, seven with primary hyperparathyroidism, and one with an excluded gastric antrum, intravenous secretin 3 U/ kg/hour for 90 minutes increased total protein and the protein-bound calcium fraction but did not alter the ionized calcium fraction (6). 

Cholecystokinin Secretin Intrinsic Factor Gastric Acid... 

Neuniicnsin is a 13-amino-acid peptide, nrsi Lsolaled from bovine hypothalamus, ll has now been identified in Ihc intestinal tract. The ileal muco.sa contains 90 % of the total neurotensin of ihe body. It is implicated as a releasing factor for several adenohypophyscal honnones. ll cairscs vasodilatation. increa.ses va.scular penneabilily. and increases ga.sirin secretion. It decreases. secretion of gastric acid and secretin. 

Gastric acid secretion can be inhibited by several mechanisms including acid in the stomach (pH 3 inhibits gastrin release), acid in the duodenum, the presence of fat in the pancreas, and hypertonic fluids or hyperglycemia. Somatostatin, a hormone produced by antral mucosal endocrine cells (D cells), inhibits the release of gastrin by directly inhibiting the parietal cells. Somatostatin is also present in other GI tissue and the pancreas. C cells, endocrine cells in the proximal small intestine, secrete secretin in response to mucosal acidification, which also decreases gastric secretion. 

The duodenum is the shortest part of the small intestine, where most chemical digestion occurs. The duodenum releases secretin, a hormone, which suppresses gastric acid. Cholecystokinin, a hormone, is released by the duodenum that simulates flow of bile from the gallbladder into the duodenum. Bile (produced by the liver), trypsin, chymotrypsin, lipase, and amylase (all produced by the pancreas) digest carbohydrates, protein, and fat in preparation for absorption in the small intestine. The duodenum connects the stomach to the jejunum. The jejunum is the second division of the small intestine and connects the duodenum to the ileum. The ileum is the end of the small intestine. 

Suppression of secretion of many hormones (e.g., GH, TSH, gastrin, vasoactive intestinal polypeptide [VIP], gastric inhibitory polypeptide [GIP], secretin, motilin, glucagon, and insulin)... 

Gastrins stimulate the secretion of gastric acid, pepsinogen, intrinsic factor, and secretin stimulate intestinal mucosal growth increase gastric and intestinal motility... 

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