淋巴系統概述，動畫(The Lymphatic System Overview, Animation). 72 4. Amy. ... 英 ...Inanutshell,thelymphaticsystemisadrainagesystemthatremovesexcessfluidfrombody中tissuesandreturnsittothebloodstream.中Itisactuallyasubsystemofboththecirculatoryandimmunesystem.Themajorpurposeofthecirculatorysystemistobringoxygenandnutrientstobodytissuesandremovewastes.Thisexchangehappensinthesmallestbloodvesselscalledthecapillaries.Bloodplasmacontainingnutrientsmovesoutofcapillariesatthearterialendofcapillarybeds,whiletissuefluidcontainingwastesreabsorbsbackinatthevenousend.However,notallofthefluidisdrawnbacktothebloodstreamatthispoint.About15%ofitisleftinthetissuesandwouldcauseswellingifaccumulated.Thisiswherethelymphaticsystemcomesintoplay,itpicksuptheexcessfluidandreturnsittothecirculatorysystem.Unlikethebloodcirculatorysystem,whichisaclosedloop,thelymphaticsystemisaone-direction,open-endednetworkofvessels.Lymphaticvesselsbeginaslymphaticcapillariesmadeofoverlappingendothelialcells.Theoverlappingflapsfunctionasaone-wayvalve.Whenfluidaccumulatesinthetissue,interstitialpressureincreasespushingtheflapsinward,openingthegapsbetweencells,allowingfluidtoflowin.Aspressureinsidethecapillaryincreases,theendothelialcellsarepressedoutward,closingthegaps,thuspreventingbackflow.Unlikebloodcapillaries,thegapsinlymphaticcapillariesaresolargethattheyallowbacteria,immunecellssuchasmacrophages,andotherlargeparticlestoenter.Thismakesthelymphaticsystemausefulwayforlargeparticlestoreachthebloodstream.Itisused,forexample,fordietaryfatabsorptionintheintestine.Onceinsidelymphaticvessels,therecoveredfluidiscalledlymph.Lymphflowisenabledbythesameforcesthatfacilitatebloodflowintheveins.Itgoesfromlymphaticcapillariestolargerandlargerlymphaticvesselsandeventuallydrainsintothebloodstreamviathesubclavianveins.Ontheway,itpassesthroughanumberoflymphnodes,whichserveasfilters,cleansingthefluidbeforeitreachesthebloodstream.Lymphnodesaresmallbean-shapedstructuresscatteredthroughoutthelymphaticnetwork.Theyaremostprominentintheareasw