复旦生理学课件 (6).ppt

,Chapter6,DIGESTION&ABSORPTION,1.IntroductionConceptofdigestion&absorption*Mechanical&chemicaldigestionCharacteristicsofdigestivesmoothmuscles*Generalcharacteristics*ElectrophysiologicalcharacteristicsRestingpotential(RP)Slowwaveorbasicelectricalrhythm(BER)Actionpotential(AP),Electricalactivities&contractionofdigestivesmoothmuscles,Secretionofdigestiveglands*MainfunctionsofdigestivefluidsGastrointestinalinnervation*Intrinsic(orenteric)nervoussystemSubmucosal&myentericplexus*ExtrinsicnervoussystemParasympathetic&sympatheticnervesGastrointestinalhormones*Generalfunctions*Brain-gutpeptides,Intrinsic(orenteric)nervoussystem,Extrinsicnervoussystem,2.Digestioninthemouthdigeststarch*RegulationofsalivarysecretionPureneuroregulationConditioned&unconditionedreflex,MasticationorchewingaidswallowingDeglutitionorswallowing*Definition*Process1st,2nd&3rdphasePeristalsis&loweresophagealsphincter,Peristalsisoftheesophagus,3.DigestioninthestomachGastricjuice&itssecretion*Nature,Compositions&functionspH0.91.5,colorless,1.52.5L/dayHydrochloricacid(HCl)SecretedbyparietalcellsBasicsecretion:05mmol/hMaxsecretion:2025mmol/hMechanismofHClsecretionFunctions:seenextpage,RelationshipbetweenmaxvolumeofHClsecretion&thenumberofparietalcells,FunctionsofHCl:TurnpepsinogenintopepsinPromotetheabsorptionofcalcium&ferrumPepsinogenSecretedbychiefcells&activatebyHClFunction:digestproteinsintoproteoses,peptones,polypeptides,withlittlefreeaminoacids,MucusSecretedbyneck&surfacemucouscells,cardiac&pyloricglandsFunction:formmucus-bicarbonatebarrierIntrinsicfactorSecretedbyparietalcellsFunction:PromotetheabsorptionofVitB12*RegulationofgastricsecretionEndogenousreleasingsubstancesAcetylcholine(ACh),gastrin&histamineSomatostatin(SST)(release-inhibiting),Mucus-bicarbonatebarrier,Actionofacetylcholine,gastrin&histamineontheperietalcells,GastricsecretioninthedigestivephaseCephalicphaseMechanisms:Conditioned&UnconditionedreflexVagalefferent&withGastrinsecretionthroughgastrin-releasingpeptide(GRP)Experiment:ShamfeedingbyPavlovCharacteristics:Largequantity(30%)Highacidity&digestivepower,ExperimentofShamfeedingbyPavlov,GastricphaseMechanisms:Distensionofgastricfundus&bodyinitiatingvagovagal&localplexusreflexesDistensionofpylorusinitiatingareleaseofgastrinthroughintrinsicplexusChemicalstimulationofGcellsinitiayingareleaseofgastrinExperiment:PavlovpouchCharacteristics:Largequantity(60%)Highacidity&digestivepower,Heidenhain(R)&Pavlov(L)pouch,IntestinalphaseMechanisms:MainlyhumoralregulationChemical&MechanicalstimulationinitiatingreleasesofGastrin,Entero-oxyntin&OtherhumoralfactorsExperiment:PavlovpouchCharacteristics:Smallquantity(10%)Loweracidity&digestivepower,Cephalic,gastric,&intestinalphaseofgastricjuicesecretion,Summaryofcephalic,gastric,&intestinalphaseofgastricjuicesecretion,InhibitoryregulationHydrochloricacid(HCl)AtypicalexampleofnegativefeedbackConditions&Mechanisms:pH1.21.5inthegastricantrumInhibitionofGcells,ReleaseofSSTpH2.5intheduodenumReleaseofsecretin,bulbogastroneFat:InitiatingreleaseofenterogastroneHypertonicsolution:Entero-gastricreflex,Gastricmotility&emptying*MaintypesofgastricmotilityToniccontractionMaintainingtheshape&placeofstomach,aswellastheintragastricpressureReceptiverelaxationDefinition&itsinnervationPeptideorNOergicvagalfibersGastricperistalsisInitiatefrommiddlestomach,3times/minMix&grindfoodintochyme&helpempty,*Gastricemptying&itscontrolDefinition&somerulesCarbohydrateproteinslipids,Mix46hDiscontinuousemptyingAdaptingfordigestion&absorptionControlofemptyingPromotioninstomach:vagovagal&plexusreflex,gastrinreleaseInhibitioninduodenum:entero-gastricreflex&enterogastrone,*GastricmotilityinthedigestiveinterphaseMigratingmotorcomplex(MMC)PhaseI:restingphase,90120minPhaseII:irregularspike&sporadicperistalsis,3045minPhaseIII:largeamountofspikes®ularstrongcontraction,510minPhaseIV:transitionperiod,about5minSignificance:actasastreetcleanerVomitingDefinition:areflex,benefit&harm,Migratingmotorcomplex(MMC),4.DigestionintheintestinePancreaticjuice&itssecretion*Nature,Compositions&functionspH7.88.4,colorless&odourless,12L/dayBicarbonate(HCO3)NeutralizeHCl&provideaweakbasicmediumfavoringdigestiveenzymeactionPancreaticenzymes:amylase,lipase,colipase,trypsinogen&chymtrypsinogen,etc.Turntrypsinogenintotrypsinbyentero-kinase,turnchymtrypsinogenintochym-trypsinbytrypsinTrypsininhibitor:apolypeptide,*RegulationofpancreaticsecretionNervousregulationVagusnerve:ACh,gastrinCharacteristics:H2O&HCO3,enzymesSympatheticnerve:ACh,NACharacteristics:weakeffectHumoralreulationSecretin:H2O&HCO3,enzymesCholecystokinin(CCK):Characteristics:H2O&HCO3,enzymesFeedback:CCK-releasingpeptide,BilesecretionPromotetheabsorptionoffat-solubleVits,*ControlofbilesecretionindirecttostomachHClsecretinSecretin:acttobileduct¬tohepaticcells,so:H2O&HCO3,bilesalt()Cholecystokinin(CCK):gallbladdercontraction&OddissphincterdialationBilesalt:enterohepaticcirculationofbilesalt,Enterohepaticcirculationofbilesalt,Secretionofthesmallintestine*IntestinalglandsBrunnersgland(basicmucus)LieberkuhnCrypt(mainpart)*Nature,Compositions&functionspH7.6,iso-osmoticsolution,13L/dayEnterokinase,theonlyonesecretedOligopeptidase,oligosaccharidasethosecontainedintheepithelialcells*RegulationofsecretionofsmallintestineMainlythroughplexusreflexinitiatedbyinflationoftheintestine,Movementsofthesmallintestine*MovementinthedigestiveinterphaseMMCsimilartothatinthestomach*MainmovementformsindigestivephaseToniccontraction:thesameasinstomachSegmentation:peculiartothesmallintestinePeristalsis:0.52.0cm/sPeristalticrush:225cm/s*Regulationofsmallintestinalmovement,Segmentationofthesmallintestine,*RegulationofsmallintestinalmovementIntrinsicplexus:receivemechanicalsympatheticneverintestinalactivitiesHumoralfactors:gastrin,CCK,Enk,5-HT,etc.Functionsoftheileocecalsphincter*Permitsomeofchymetosquirtintothececumeachtimewhenaperistalsiswavereachesit*Preventrefluxofcoloniccontentsintotheileum,5.DigestioninthecolonMainfunctionofthecolonAbsorbwaterAbsorbVitB&KsynthesizedbybacteriaFormation&temporarilystoragefecesSecretionofthecolonpH8.38.4,Mucus&HCO3Protectmucosaagainstinjuries&lubricatefecesMovementsofthecolonHaustraltoandfromovement,SegmentationorPolyhaustralpushingmovement,Peristalsis,Massperistalsis,FecesLowthecaloricratioofthefood,6.AbsorptioninthesmallintestineSitesofabsorptionOralcavity&Stomach:littleDuodenum&Upperjejunum:mostnutrientsIleum:bilesalts&Vit.B12Colon:water&electrolytesProofsasthemainabsorptiveregionHugeabsorptivesurface(200m2)Plentyofcapillaries&lymphcapillariesLargequantityofdige