呼吸科呼吸系统3课件

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1、5.3.GastransportOxygenistransportedbythebloodinbothphysicallydissolvedandhemoglobin-bondforms.Carbonmonoxidebindsthesamesiteonhemoglobinasoxygendoesandisdangeroustolife.Carbondioxide(CO2)istransportedinthreeforms:physicallydissolved,bicarbonate,andcarbaminohemoglobin2021/9/41O

2、xygenTransportintheBlood2021/9/422021/9/43Hemoglobin(Hb)EachHbmoleculeconsistsoffourglobularprotein(globin,珠蛋白)subunits.Eachsubunitiscomposedofaproteinchaintightlyassociatedwithanon-proteinheme（血红素）group.Oxygenbindstoiron(Fe2+)onheme.TwoFormsofOxygenExistintheBloodPhysicallydi

3、ssolved:2%DissolvedO2(ml/dL)=0.003(ml/dL/mmHg)XPaO2(mmHg)CombinedwithHb:98%Bothphysicallydissolvedandchemicallybondareimportant.Oxyhemoglobin(HbO2):Hemoglobinbindstooxygen.Deoxyhemoglobin(Hb):Hemoglobinthatdoesnotbindwithoxygen.2021/9/44OxygenBindstoHemoglobinThebindingofoxyge

4、ntohemoglobinisreversibleandveryquick.Thereactionofthisbidingisoxygenationbutnotoxidation(ferrousremainsasferrous).Eachhemoglobinmoleculecanbindfouroxygenmolecules.Eachgramofhemoglobincanbindup1.34~1.39mlofO2(dependingonmethemoglobinlevels).2021/9/45PositiveCooperativityChange

5、sintheaffinityofhemoglobinaseachsuccessiveO2moleculebindstoahemesite.BindingofthefirstO2moleculeincreasestheaffinityforthesecondO2molecule,andsoforth.TheaffinityfortheforthO2moleculeisthehighest.ThischangeinaffinityfacilitatestheloadingofO2inthelungsandtheunloadingoftheO2atthe

6、tissues.2021/9/46QuantitativeDescriptionofO2BindingtoHbOxygencapacityisthemaximumofoxygenthathemoglobincancarryper100mlblood.Hb-boundoxygencontentistheamountofoxygenactuallycarriedbyhemoglobinper100mlblood.Oxygensaturation(SO2)isthepercentagesaturationofhemoglobinwithoxygentha

7、tiscalculatedfromtheratioofoxygencontentovercapacity.TherelationshipbetweenandPO2andSO2(oroxygencontent)isoxyhemoglobinequilibriumcurve(oxygendissociationcurve).2021/9/47OxygenDissociationCurve2021/9/48AnalysisofOxygenDissociationCurveWhenPaO2isincreasedfrom60and100mmHg,SaO2ri

8、sesonlyby7%.Theclinicalsignificanceoftheflatportionofoxygendi