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1、Digestioninthesmallintestine1.pancreaticsecretion㈠.Compositionandfunctionofpancreaticjuice:pH7.8-8.4,isotonic,1-2L/d1.HCO3-:largequantityofalkalineionscanneutralizetheacidfromstomach2.Digestiveenzyme:(1)pancreaticamylase(pH6.7–7.0)(2)a.pancreaticlipaseb.colipasec.phosph
2、olipaseA2d.esterase(3)trypsin(activatedbyenterokinase&itself)andchymotrypsin(activatedbytrypsin)(4)other:carboxypolypeptidase,ribonuclease,deoxyribonuclease㈡．Regulationofpancreaticsecretion1.Neuralregulation:vagalN,Ach,gastrin→pancreaticjuice↑Characteristics:H2O,HCO3-lo
3、w;enzyme↑2.Humoralregulation:a.secretinCharacteristics:H2O,HCO3-↑,enzymelow;HCl>proteindigestiveproducts>fattyacidb.CCKCharacteristics:H2O,HCO3-↓,enzyme↑proteindigestiveproducts>fattyacid>HCl>fatCCK→bileexcretionfromgallbladderc.gastrin,VIP→pancreaticsecretion↑二．Secreti
4、onandexcretionofthebile㈠.Compositionofthebile:bilesalt,bilirubin,胆红素cholesterol,lecithin卵磷脂,water,ions,etc.noanyenzyme㈡.Bilefunction1.Promotedigestionandabsorptionoffat(bilesalt)(1)decreasethesurfacetensionofthefatparticlesincreasethetotalsurfaceareaonwhichlipasecanact(
5、2)bilesalt+fattyacid+monoglycerides=micelles→highlysoluble2.protectcholesterolfromdepositingingallbladder3.promotetheabsorptionofliposolublevitaminA.D.K.E4.promotethesynthesisandsecretionofbileEnterohepaticcirculationofbilesalt㈢.ControlofbilesecretionandexcretionNatural
6、stimulation:chymeingastrointestinal:(protein>fat/mixture>glucose)1.Neuralcontrol:vagus(+)→gastrin↑→bile↑,gallbladderexcretionbile↑2.Humoralcontrol:a.gastrin→hepaticcells&gallbladder→bile↑b.secretin→bile↑(HCO3↑,butbilesaltnoincrease)c.CCK→gallbladdercontraction,oddisphin
7、cterrelaxation→bileoutputd.bilesalt:enterohepaticcirculation→hepaticbile↑about94%bilesaltcanbereabsorbedbytheintestinalmucosainthedistalileumeachcirculation四．MotilityofsmallintestineMotilityformofsmallintestine:1.toniccontraction2.segmentation3.peristalsis
