搜索
respiration第五章呼吸生理1.外呼吸肺通气（外界空气与肺泡之间的气体交换过程）肺换气(肺泡与肺毛细血管之间的气体交换过程）呼吸的三个基本环节2.气体在血液中的运输3.内（组织）呼吸血液与组织、细胞之间的气体交换过程肺通气和肺换气6Thegoalsofrespirationaretoprovideoxygentothetissuesandtoremovecarbondioxide.Toachievethesegoals,respirationcanbedividedintofourmajorfunctionalevents:7(1)pulmonaryventilation,whichmeanstheinflowandoutflowofairbetweentheatmosphereandthelungalveoli;(2)diffusionofoxygenandcarbondioxidebetweenthealveoliandtheblood;8(3)transportofoxygenandcarbondioxideinthebloodandbodyfluidstoandfromthecells;and(4)regulationofventilationandotherfacetsofrespiration.Thischapterisadiscussionofpulmonaryventilation.第一节肺通气一、实现肺通气的结构特点及功能鼻、咽、喉、气管直到终末细支气管上呼吸道{下呼吸道二、肺通气原理（一）肺通气的动力直接动力：肺泡与大气之间的压力差原动力:呼吸运动呼吸肌收缩、舒张所造成的胸廓的扩大和缩小，称为呼吸运动。1．呼吸运动（1）吸气运动：膈肌收缩时中部下移，增大了胸腔的上下径，肺容积随之增大，产生吸气。平静呼吸时膈肌收缩造成的通气量占总通气量的4/5。当肋间外肌收缩时，增大了胸腔的前后径和左右径，肺容积随之增大,产生吸气。（2）呼气运动：平静呼气时，因膈肌和肋间外肌舒张，肺依靠本身的回缩力量而回位，产生呼气。用力呼吸：除上述肌肉外，有更多的吸气肌与呼气肌参与呼吸运动。用力呼吸{吸气（主动）膈肌和肋间外肌收缩，胸锁乳突肌、斜角肌也收缩呼气（主动）膈肌和肋间外肌舒张，腹壁肌肉、肋间内肌收缩平静呼吸{吸气（主动）膈肌和肋间外肌收缩呼气（被动）膈肌和肋间外肌舒张呼吸运动{腹式呼吸胸式呼吸膈肌舒缩引起的呼吸运动伴以腹壁的起伏，所以称为腹式呼吸（abdominalbreathing）。由肋间肌舒缩使肋骨和胸骨运动所产生的呼吸运动，称为胸式呼吸。Thoracicbreathing261.MechanicsOfPulmonaryVentilation627.4-628.3A.MusclesThatCauseLungExpansionandContraction629.2-630.227Thelungscanbeexpandedandcontractedintwoways:bydownwardandupwardmovementofthediaphragmtolengthenorshortenthechestcavityandbyelevationanddepressionoftheribstoincreaseanddecreasetheantero-posteriordiameterofthechestcavity.28Normalquietbreathingisaccomplishedalmostentirelybythefirstofthetwomethods,thatis,bymovementofthediaphragm.Duringinspiration,contractionofthediaphragmpullsthelowersurfacesofthelungsdownward.29Then,duringexpiration,thediaphragmsimplyrelaxes,andtheelasticrecoilofthelungs,chestwall,andabdominalstructurescompressesthelungs.30Duringheavybreathing,however,extraforceisachievedmainlybycontractionoftheabdominalmuscles,whichpushestheabdominalcontentsupwardagainstthebottomofthediaphragm.31Thesecondmethodforexpandingthelungsistoraisetheribcage.whentheribcageiselevated,makingtheantero-posteriorthicknessofthechestabout20percentgreaterduringmaximuminspirationthanduringexpiration.32Therefore,allthemusclesthatelevatethechestcageareclassifiedasmusclesofinspiration,andthemusclesthatdepressthechestcageareclassifiedasmusclesofexpiration.Themostimportantmusclesthatraisetheribcagearetheexternalintercostals.33Themusclesthatpulltheribcagedownwardduringexpirationare(1)theabdominalrecti,whichhavethepowerfuleffectofpullingdownwardonthelowerribsatthesametimethattheyandtheotherabdominalmusclescompresstheabdominalcontentsupwardtowardthediaphragm,and(2)theinternalintercostals.34Astheexternalintercostalstheycontract,theypullribsforward,andthiscausesleverageontheribstoraisethemupward,therebycausinginspiration.Theinternalintercostalsfunctionexactlyoppositely,functioningasexpiratorymuscles,becausetheyanglebetweentheribsintheoppositedirectionandcauseoppositeleverage.2．肺内压肺内压是指肺泡内的压力。吸气初，肺内压低于大气压，空气进入肺泡。呼气初，肺内压高于大气压，肺内气体流出。吸气末和呼气末，肺内压和大气压相等。36Alveolarpressureisthepressureoftheairinsidethelungalveoli.Whentheglottis声门isopenandnoairisflowingintooroutofthelungs,thepressuresinallpartsoftherespiratorytree,allthewaytothealveoli,areequaltoatmosphericpressure,whichisconsideredtobethezeroreferencepressureintheairways–thatis,0centimeterswaterpressure.37Tocauseinwardflowofairintothealveoliduringinspiration,thepressureinthealveolimustfalltoavalueslightlybelowatmosphericpressure(below0).38Duringnormalinspiration,alveolarpressuredecreasestoabout-1centimeterofwater.Thisslightnegativepressureisenoughtopull0.5literofairintothelungsinthe2secondsrequiredfornormalquietinspiration.39Duringexpiration,oppositechangesoccur:Thealveolarpressurerisestoabout+1centimeterofwater,andthisforcesthe0.5literofinspiredairoutofthelungsduringthe2to3secondsofexpiration.3.胸内压胸膜腔内的压力称为胸内压。胸膜腔内压比大气压低，为负压。平静呼气末胸膜腔内压约为-5—-3mmHg，吸气末约为-10—-5mmHg。胸内压=大气压-肺回缩力胸内压=肺内压-肺弹性回缩力=大气压-肺弹性回缩力若以1个大气压为0，则胸膜腔内压=－肺弹性回缩力46Pleuralpressureisthepressureofthefluidinthenarrowspacebetweenthelungpleuraandthechestwallpleura.47Pleuralpressureisnormallyaslightlynegativepressure.Thenormalpleuralpressureatthebeginningofinspirationisabout-5centimetersofwater,whichistheamountofsuctionthatisrequiredtoholdthelungsopentotheirrestinglevel.48Then,duringnormalinspiration,theexpansionofthechestcagepullsoutwardonthelungswithstillgreaterforceandcreatesastillmorenegativepressuretoanaverageofabout-7.5centimetersofwater.（二）肺通气的阻力{弹性阻力（70%）非弹性阻力（30%）1、弹性阻力和顺应性（1）弹性阻力弹性组织在外力作用下变形时，有对抗变形和弹性回位的倾向，为弹性阻力。（2）顺应性(compliance)顺应性是指在外力作用下弹性组织的可扩张性。容易扩张者，顺应性大，弹性阻力小；反之则相反。可见顺应性（C）与弹性阻力（R）成反变关系：C=1/R顺应性用单位压力变化（△P）所引起的容积变化（△V）来表示，单位是L/cmH2O，即C=△V/△PL/cmH2O。54Complianceintherespiratorysystem631.2-633.1•describesthedistensibilityofthelungsandchestwall.•isinverselyrelatedtoelastance,whichdependsontheamountofelastictissue.•isthechangeinvolumeforagivenchangeinpressure.•肺的弹性阻力{肺表面张力（2/3）肺组织弹性（1/3）(3)肺的弹性阻力的来源肺组织的弹性主要来肺组织的弹性纤维和胶原纤维。57Resistencetopulmonaryventilation633.2-634.4Resistantforcesofthelungs.Thesecanbedividedintotwoparts:(1)theelastic