小肠内消化Digestioninthesmallintestine胰液.PPT

Digestion in intestine YU Yanqin, PhD Zhejiang University, School of Medicine Pancreatic secretion Pancreatic juice (胰液) pH 7.8~8.4 ~1500 ml/day Isosmotic Components: Pancreatic digestive enzymes（胰消化酶）: secreted by pancreatic acini Sodium bicarbonate（碳酸氢钠）: secreted by small ductules and larger ducts Secretion of bicarbonate ions Secreted by the epithelial cells of the ductules （小叶导管） and ducts that lead from acini （腺泡） Up to 145mmol/L in pancreatic juice (5 times that in the plasma) Function: Neutralizing acid entering the duodenum（十二指肠） from the stomach Secretion of pancreatic digestive enzymes Carbohydrates -- Pancreatic amylase （胰淀粉酶） Pancreatic lipase （胰脂肪酶） Fat Cholesterol esterase Phospholipase Trypsinogen（胰蛋白酶原） Proteins Chymotrypsinogen （糜蛋白酶原） Procarboxypolypeptidase （羧基肽酶） Proelastase （弹性蛋白酶） Trypsin (胰蛋白酶) Inhibitor Inhibits the activity of trypsin and thus guards against the possible activation of trypsin and the subsequent autodigestion of the pancreas Acute pancreatitis (胰腺炎) Acute pancreatitis Regulation of pancreatic secretion Basic stimuli that cause pancreatic secretion Ach Cholecystokinin （胆囊收缩素/促胰酶素）: Secreted by I cells Stimulates the acinar cells to secrete large amounts of enzymes Secretin（促胰液素）: Released by S cells Acts primarily on the duct cells to stimulate the secretion of a large volume of solution with a high HCO3-(Bicarbonate) concentration Regulation of pancreatic secretion Phases of pancreatic secretion Cephalic Phase 头期 Gastric Phase 胃期 Intestinal Phase 肠期 Regulation of pancreatic secretion Cephalic Phase An autonomic reflex response to stimulation of olfactory and taste receptors Stimulation of the acinar cells by ‘long’ parasympathetic pathways, which release ACh Regulation of pancreatic secretion Gastric Phase Distension of the stomach causes increased pancreatic secretion via the release of ACh by ‘long’ parasympathetic refl