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1、Chapter5RespiratorySystemInthispassageyouwilllearn:●Theorgansoftherespiratorysystem●Thestructureandfunctionoftheseorgans●Themechanismofbreathing●ThegastransportandcleaningsystemAlllivinganimalsmusttakeinoxygenandgetridofcarbondioxide.Inthevertebrates——animalswithbackbones——that
2、gettheiroxygenfromtheair,bothtasksareperformedbyspecialgas-exchangeorganscalledlungs.Thelungsprovideaplacewhereoxygencanreachthebloodandcarbondioxidecanberemovedfromit.Theyareequippedwithtubesandabellowssystemfordrawinginairfromtheoutside,whilethepulmonaryveinsandarteriescircul
3、atebloodthroughfrominside.Thelungsalsohaveacleaningsystemthattraps,ejects,ordestroysirritantsandotherharmfulsubstancesthattravelinwiththeair.Inthesimplercold-bloodedamphibiansandreptiles,thelungsaretwoballoon-likesacs.Inactiveanimalsthatrequirelargeamountsofoxygen,especiallythe
4、warm-bloodedbirdsandmammals,thelungsareaspongylabyrinthofsacsthatsupplyanenormoussurfaceareaforthetransferofgases.Intheadulthumanthetotallungsurface,ifflattenedout,wouldbelargerthanabadmintoncourt,about100squareyards(83squaremeters).Airentersthebodythroughthenoseandpassesthroug
5、hthenasalcavity,whichislinedwithamucousmembraneandfinehairs(cilia)tohelpfilteroutforeignbodies,aswellastowarmandmoistentheair.Paranasalsinusesarehollow,air-containingspaceswithintheskullthatcommunicatewiththenasalcavity.They,too,haveamucousmembraneliningandfunctiontoprovidethel
6、ubricatingfluidmucus.aswellastolightenthebonesoftheskullandhelpproducesound.Afterpassingthroughthenasalcavity,theairnextreachesthepharynx(throat).Therearethreedivisionsofthepharynx.Thenasopharynxisthefirstdivision,anditisnearesttothenasalcavities.Itcontainstheadenoids,whicharem
7、assesoflymphatictissue.Theadenoids(alsoknownasthepharyngealtonsils)aremoreprominentinchildren,andifenlarged,theycanobstructairpassageways.Belowthenasopharynxandclosertothemouthistheseconddivisionofthepharynx,theoropharynx.Thepalatinetonsils,tworoundedmassedoflymphatictissue,are
8、locatedintheoropharynx.Thethirddivisionofthepharynxist