呼吸科呼吸系统课件3.ppt

呼吸科呼吸系统课件3.ppt

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5.3.Gastransport5.3.GastransportlOxygenistransportedbythebloodinbothphysicallydissolvedandhemoglobin-bondforms.lCarbonmonoxidebindsthesamesiteonhemoglobinasoxygendoesandisdangeroustolife.lCarbondioxide（CO2）istransportedinthreeforms:

physicallydissolved,bicarbonate,andcarbaminohemoglobin2022/11/41OxygenTransportintheBlood2022/11/422022/11/43Hemoglobin（Hb）EachHbmoleculeconsistsoffourglobularprotein（globin,珠蛋白）subunits.Eachsubunitiscomposedofaproteinchaintightlyassociatedwithanon-proteinheme（血红素）group.Oxygenbindstoiron（Fe2+）onheme.TwoFormsofOxygenExistintheTwoFormsofOxygenExistintheBloodBloodPhysicallydissolved:

2%DissolvedO2（ml/dL）=0.003（ml/dL/mmHg）XPaO2（mmHg）CombinedwithHb:

98%Bothphysicallydissolvedandchemicallybondareimportant.Oxyhemoglobin（HbO2）:

Hemoglobinbindstooxygen.Deoxyhemoglobin（Hb）:

Hemoglobinthatdoesnotbindwithoxygen.2022/11/44OxygenBindstoHemoglobinOxygenBindstoHemoglobinThebindingofoxygentohemoglobinisreversibleandveryquick.Thereactionofthisbidingisoxygenationbutnotoxidation（ferrousremainsasferrous）.Eachhemoglobinmoleculecanbindfouroxygenmolecules.Eachgramofhemoglobincanbindup1.341.39mlofO2（dependingonmethemoglobinlevels）.2022/11/45PositiveCooperativityPositiveCooperativityChangesintheaffinityofhemoglobinaseachsuccessiveO2moleculebindstoahemesite.BindingofthefirstO2moleculeincreasestheaffinityforthesecondO2molecule,andsoforth.TheaffinityfortheforthO2moleculeisthehighest.ThischangeinaffinityfacilitatestheloadingofO2inthelungsandtheunloadingoftheO2atthetissues.2022/11/46QuantitativeDescriptionofOQuantitativeDescriptionofO22BindingtoHbBindingtoHbOxygencapacityisthemaximumofoxygenthathemoglobincancarryper100mlblood.Hb-boundoxygencontentistheamountofoxygenactuallycarriedbyhemoglobinper100mlblood.Oxygensaturation（SO2）isthepercentagesaturationofhemoglobinwithoxygenthatiscalculatedfromtheratioofoxygencontentovercapacity.TherelationshipbetweenandPO2andSO2（oroxygencontent）isoxyhemoglobinequilibriumcurve（oxygendissociationcurve）.2022/11/47OxygenDissociationCurveOxygenDissociationCurve2022/11/48AnalysisofOxygenDissociationCurveAnalysisofOxygenDissociationCurveWhenPaO2isincreasedfrom60and100mmHg,SaO2risesonlyby7%.TheclinicalsignificanceoftheflatportionofoxygendissociationcurveisthatadropPO2from100to60mmHgstillresultsinhemoglobinsaturationof90%.RisingPaO2above100mmHgbarelyaffectsoxygencontent.Inthesteepportionofthiscurve,bloodoxygencontentandthusoxygendeliverytotissuesarecompromiseduponPO2fallsbelow60mmHg.ThesignificanceofthisportionofthecurveisthatalargeamountofO2isreleasedfromhemoglobinwithasmallchangeinPO2.2022/11/49ChangesinBloodChemistryAlterChangesinBloodChemistryAlterHemoglobinsAffinityforOHemoglobinsAffinityforO222022/11/410TorememberJustthinkthatanexercisingmuscleishotandacidicandproduceslargeamountofcarbondioxide,allofwhichfavortheunloadingofmoreoxygentothemetabolicneedsofmusclesDPG=2,3-diphosphoglycerateBohrEffectBohrEffectlBohreffect（aftertheDanishphysiologist,ChristinBohr）referstotheeffectofCO2ontheaffinityofhemoglobinonoxygen.lIncreasedCO2shiftstheoxyhemoglobindissociationcurvetotheright,promotingoxygenrelease.lBohreffectiscausedinpartbythechangeinpHthatoccursasCO2increases.2022/11/411PP5050IndicatestheBindingActivityofIndicatestheBindingActivityofHemoglobinforOHemoglobinforO22lThePO2valueatwhich50%ofhemoglobinissaturated.lThenormalrangeisbetween26and28mmHginarterialblood.lHighP50allowsmoreO2tobereleased.2022/11/412CarbonMonoxidePoisoning2022/11/413PropertiesofCarbonDioxidePropertiesofCarbonDioxide2022/11/414lCOisanodorless,colorless,andnon-irritatinggas;itisvirtuallyundetectablelCOisproducedbyincompletecombustionlWithenoughO2,CO2isgeneratedlWithlessO2,COisgeneratedCarbonMonoxideBindstotheSiteofCarbonMonoxideBindstotheSiteofHbasOxygenDoesHbasOxygenDoes2022/11/415lItbindstoHbatthesamesiteasoxygendoes,formingcarboxyhemoglobin（HgbCO）andpreventingO2binding.lThebindingaffinityforCOis200-250timesasthatforoxygen.CarbonMonoxide-HemoglobinDissociationCarbonMonoxide-HemoglobinDissociationCurveCurve2022/11/416CarbonMonoxideReducesOCarbonMonoxideReducesO22ContentContent2022/11/4172022/11/417HigherConcentrationofHigherConcentrationofCarboxyhemoglobininCigaretteSmokersCarboxyhemoglobininCigaretteSmokersInhealthyindividuals,carboxyhemoglobinoccupies12%oftheHbbindingsitesInpeoplewhosmokecigarettes,occupationofHbbindingsitescanbeincreasedupto10%Stopsmoking2022/11/418NoHype