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Gastrointestinal Physiology

Gastrointestinal Physiology. It is important to understand GI function.
1.Mastication stimulates production of the saliva by oral salivary glands.Mastication stimulates gastric secretion of Pepsin and water.Distention of the esophagus stimulates the oral salivary glands.Distention of the gastric fundus stimulates secretion of the Pepsin, HCL, Intrinsic Factor and water.Distention of the antrum stimulates Gastrin secretion. 
Distention of the duodenum stimulates secretion of the Pepsin, HCL, Intrinsic Factor and water
Antral drainage inhibit secretion of the  Pepsin, HCL, Intrinsic Factor and water
 
Chemical stimulations:
 
Stomach:
Gastrin amplifies antral production of the HCL, IF, Pepsin and water
Gastrin amplifies duodenal secretion of Cholecystokinin
 
HCL inhibit production of Gastrin.HCL stimulates secretion of Secretin by duodenum
 
Duodenum:
Gastrin stimulate the formation of the Cholecystokinin.Lipids in the jejunum stimulate secretion of the Cholecystokinin.Carbohydrates and HCL in duodenal bulb stimulate secretion of the Cholecystokinin.Cholecystokinin induce gallbladder contraction and opening of the hepatopancreatic ampulla.
Cholecystokinin stimulates production of the Insulin, HCO3, Glucagon in the pancreas
Cholecystokinin inhibit antral secretions and bulbar acidity.Secretin reduce HCL production and stimulate HCO3 production by pancreas which protect duodenal bulb from acid.Secretin stimulate Insulin release and inhibit Glucagon release.Duodenum also secretes mucus for protection from destructive effect of HCL.
Hypertonic Glucose solutions, Acidity in the bulb, Lipids in the jejunum limit the formation of the HCL and diminish gastric motility.If Lipids, proteins and carbohydrates evacuated at the same time disturbing of digestive function might occurs.Enterokinase in duodenum convert into Tripsin and inhibit Action of the biliary salts.Biliary salts (weak concentration) stimulate Lipase secretion and inhibit (strong concentration) Lipase secretion. 
Gastrin Stimulates: HCL and Water secretion by stomach; secretion of Pepsin, Secretion of Intrinsic Factor, Secretion of Cholecystokinin in the duodenum.
HCL: Inhibits secretion of Gastrin; Stimulates secretion of Secretin; Stimulates production of pepsin from pepsinogen.Anti-bacterial function; Converts Ferric iron to Ferrous iron(absorbable)
Cholecystokinin: Stimulates action of biliary salts, Contraction of Gallbladder, dilatation of choledochopancreatic ampula,inhibit gastrin and HCL production; stimulates HCO3, insulin and glucagon release
Secretin: Inhibit HCL, Glucagon, stimulate Insulin release ,stimulates HCO3 production by Pancreas