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1、Chapter5RespiratorySystemInthispassageyouwilllearn:●Theorgansoftherespiratorysystem●Thestructureandfunctionoftheseorgans●Themechanismofbreathing●ThegastransportandcleaningsystemAlllivinganimalsmusttakeinoxygenandgetridofcarbondioxide.Inthevertebrates——animalswithbackbones——thatgettheiroxygen
2、fromtheair,bothtasksareperformedbyspecialgas-exchangeorganscalledlungs.Thelungsprovideaplacewhereoxygencanreachthebloodandcarbondioxidecanberemovedfromit.Theyareequippedwithtubesandabellowssystemfordrawinginairfromtheoutside,whilethepulmonaryveinsandarteriescirculatebloodthroughfrominside.Th
3、elungsalsohaveacleaningsystemthattraps,ejects,ordestroysirritantsandotherharmfulsubstancesthattravelinwiththeair.Inthesimplercold-bloodedamphibiansandreptiles,thelungsaretwoballoon-likesacs.Inactiveanimalsthatrequirelargeamountsofoxygen,especiallythewarm-bloodedbirdsandmammals,thelungsareasp
4、ongylabyrinthofsacsthatsupplyanenormoussurfaceareaforthetransferofgases.Intheadulthumanthetotallungsurface,ifflattenedout,wouldbelargerthanabadmintoncourt,about100squareyards(83squaremeters).Airentersthebodythroughthenoseandpassesthroughthenasalcavity,whichislinedwithamucousmembraneandfineha
5、irs(cilia)tohelpfilteroutforeignbodies,aswellastowarmandmoistentheair.Paranasalsinusesarehollow,air-containingspaceswithintheskullthatcommunicatewiththenasalcavity.They,too,haveamucousmembraneliningandfunctiontoprovidethelubricatingfluidmucus.aswellastolightenthebonesoftheskullandhelpproduce
6、sound.Afterpassingthroughthenasalcavity,theairnextreachesthepharynx(throat).Therearethreedivisionsofthepharynx.Thenasopharynxisthefirstdivision,anditisnearesttothenasalcavities.Itcontainstheadenoids,whicharemassesoflymphatictissue.Theadenoids(alsoknownasthepharyngealtonsils)aremoreprominenti
7、nchildren,andifenlarged,theycanobstructairpassageways.Belowthenasopharynxandclosertothemouthistheseconddivisionofthepharynx,theoropharynx.Thepalatinetonsils,tworoundedmassedoflymphatictissue,arelocatedintheoropharynx.Thethirddivisionofthepharynxist
