高中英语 Unit 5 First aid Language points素材 新人教版必修5.doc

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1、BLEEDINGBleedingiswhenoneormorebloodvesselsaredamagedandcanbefromarteries,veins,orcapillaries.Theseriousnessofthehaemorrhagedependsonthedepthofthecut,amountofbleeding,timetakentocontrolthebleeding,andtypeofbloodvesselsdamaged.Seeingyourownbloodcanbeashock,ando

2、nlookerswatchingthescenemayexperienceshock.Thecaregiverisalsoinpotentialdangerofbecominginfectedbyatransmissibledisease—forexample,HIVorhepatitis.Externalbleedingisalmostalwayseasytoidentify,butinternalbleedingisoftenmoredifficulttodetectandtreat.Anaverageadul

3、thasabout5lofbloodandcansafelylosehalfalitre.Rapidlossoflargervolumesofblood,however,leadstohypovolaemicshockanddeath.Hypovolaemicshockisaclinicalstateinwhichtissueperfusionisinadequateduetoalossofbloodorplasma.Areductioninbloodvolumecausesafallinsystolicblood

4、pressure,whichtriggersasympatheticcatecholamineresponse.Bloodflowtotheperipheriesisreduced.Anaerobicmetabolismwithlactateproductionoccursintissuesthatareinadequatelyperfusedandthiscangoontoimpairthefunctionofvitalorganssuchasthebrain,heart,andkidneys.