消化digestion and absorption 课件

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1、Chapter6DigestionandAbsorptionGastrointestinalsystemIntroduction1.Digestion:1)itisaprocessessentialfortheconversionoffoodintoaformthatcanbeutilizedbythebodyProcessbywhichfoodandlargemoleculesarechemicallydegradedtoproducesmallermoleculesthatcanbeabsorbedacrossthewallofthegastrointestinaltract.2)Me

2、chanicaldigestion:themusclescontractionsthatmixandmoveforwardthecontentsofthedigestivetract.3)Chemicaldigestion:thisprocessrequiresthesecretionofspecialenzymestocatalyzethebreakdownofvariouscomplexfoodstuffmoleculesintosmallforms.2.Absorption:itistheprocessoftransportingsmallsubstanceormoleculefrom

3、thelumenofthegutintobloodstreamorlymphatic.一．CharacteristicsofgutsmoothmuscleGutsmoothmusclegeneralcharacteristics:1.lowexcitability,2.automaticity(rhythmicalcontraction),3.tonicity,紧张性4.extensibility,5.sensitivity:moresensitivetostretch机械牵长,chemicals,coldandwarmstimulationbutnottoelectricstimulati

4、ongutsmoothmuscleelectricalactivityandcontractility:1.Restingpotential:(-50)---(-60)mv,K+,Na+,Cl-2.Slowwave----basicelectricalrhythm(BER)thesmoothmuscleoftheguthasauto-depolarizationandrepolarizationionbasis:relationtoaslowundulation起伏oftheactivityoftheNa–KpumpIntensity:5-15mV,frequency:3-12/min.3-

5、12cyclesperminutedependingonareaofGItract:3/mininstomach,12/mininduodenum十二指肠3.Actionpotential:Ca2+channel,dependonslowwaveslowwave→AP→musclecontractionContractioncurveIntracellularpotential二．Innervation神经分布ofdigestivesystemanditseffects1.Extrinsicnerve:1)sympatheticnerve(+)releasingNE→gutactive(-)

6、2)parasympatheticnerve(+)releasingAch→gutactive(+)3)peptidnerves(+)releasingVIP,substancePandsoon2.Entericnervoussystem:submucosalplexusandmyentericplexus(VIP,P,Ach)三．Functionofdigestiveglandsdialysecretionquantities:6-8LTab6-1constituents:waterelectrolytesorganicsubstanceenzymemucusetcDigestivejui

7、cefunction:1).Tocatalyzethebreakdownofvariouscomplexfoodstuffmoleculesintosimpleform.2).ToprovideoptimumpHforenzyme3).Todilutethefoodtotheosmolarityofplasmaforabsorption4).Toprotectthemucosafromphysicalandc