Intestinal Phase

Intestinal Phase - Digestive System Intestinal Phase As chyme empties from the stomach into the small intestine it initially enhances gastric

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Digestive System Intestinal Phase * As chyme empties from the stomach into the small intestine it initially enhances gastric secretion, but soon inhibits it. * the resulting distention, fat, peptides, and amino acids in the chyme activates vagovagal reflexes that (1) stimulates * intestinal contractile activity * G cells of the duodenum to secrete more gastrin * stimulate enteroendocrine cells in the mucosa of the duodenum to secrete the hormone secretin, cholecystokinin CCK), and gastric inhibitory peptide (GIP). CCK (cholecystokinin) * This hormone production is stimulated by the presence of food in the duodenum. * stimulates secretion of enzymes by pancreatic acinar cells. * induces contraction of the gallbladder and relaxation of the sphincter of Oddi. Secretin * Elevated circulating secretin stimulates bicarbonate secretion by pancreatic ductal cells that neutralizes the acidity from the stomach which is necessary for a number of enzymes to function in the breakdown and absorption of food. * It also stimulates the liver to secrete bile. GIP (Gastric Inhibitory Peptide) * Food in the duodenum stimulates certain endocrine cells to produce GIP. * It has the opposite effects of gastrin; * it inhibits gastric glands in the stomach and it inhibits the mixing and churning movement of stomach muscles (stomach motility). * This slows the rate of stomach emptying when the duodenum contains food. * enhance the release of insulin in response to infusions of glucose. * Acidic chyme and chyme that contains fat will * activate duodenal receptors which act to (4) reduce the rate of gastric emptying. * causes a reduction in gastric secretion of acid. Stomach Regions Stomach * Mucosa * Submucosa * Muscularis – 3 layers * Serosa – on all portions of stomach Tunica Mucosa.
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* A very complex histologic diversity seen in different zones that is dependent on the functions * Numerous folds or rugae * The lamina propria is difficult to delineate Submucosa * Thick layer of loose CT * Bulging of the submucosa is largely responsible for formation of the rugae Tunica Muscularis * The stomach has three layers of muscle * Inner oblique layer * Middle circumferential or circular layer * Outer longitudinal layer. * Auerbach's plexus lies between the outer two layers General Structure Glands in the Stomach * Cardiac glands - mucus ** * Gastric glands - enzyme + acid * Pyloric glands - mucus ** (differs from mucus of cardiac glands) * **Mucus differs from mucus of neck cells Stomach Regions Gastric Mucosa Gastric Glands –Neck region * The luminal portion of every gland opens into a gastric pit. This junction is known as the neck of the gland. * Columnar mucous neck cells * Stem cells – turnover time approximately 7 days Mucous Neck cells and Gastric Glands Gastric Gland Cells * Parietal (Oxyntic) Cells * Large, eosinophilic cells * Main function is the secretion of hydrochloric acid. * Chief Cell
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This note was uploaded on 01/30/2012 for the course BSC BSC1085 taught by Professor Sharonsimpson during the Fall '10 term at Broward College.

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Intestinal Phase - Digestive System Intestinal Phase As chyme empties from the stomach into the small intestine it initially enhances gastric

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