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1、ChapterFourTheRespiratorySystemTherespiratorysystemcomprisesthelungs,inwhichgaseousinterchangestakepalcebetweenthebloodandtheinspiredair,andtherespiratorytract,alongwhichairisconveyedtoandfromthelungs.Thelungsarecomposedofthebranchesoftheprincipalbronchiinthelungsandpulmonaryalveoli.Therespirato
2、rytractincludesthenasalcavity,pharynx,larynx,tracheaandbronchi.Clinicallythenasalcavity,togetherwiththepharynxandlarynxarecalledtheupperrespiratorytract;thetrachea,principalbronchiandtheirbranchesinthelungsarecalledthelowerrespiratorytract.Thebasicfunctionoftherespiratorysystemistoperformtheexch
3、angeofgasesbetweentheatmosphereandthebody,inspiringtheoxygenandexpiringthecarbondioxide.Inaddition,thelarynxisconcernedwithvoiceproduction.Figure4-1.Structureofthenasalcavity,pharynx,andlarynxinsagittalsection.Figure4-2.Respiratoryorgans.a.Insetshowsanenlargementofasectionoflung.Gasexchangesoccu
4、rsinalveolarsacs,whicharesurroundedbyacapillarynetwork.Noticethatthepulmonaryarteriolecarriesoxygen-poorblood(coloredblue)andthatthepulmonaryvenulecarriesoxygen-richblood(coloredred)Section1:ExternalRespiratoryTract1.NoseThenosecontainstwonostrils,openingsthatenterthenasalcavities.Thenasalcaviti
5、esarenarrowcanalsseparatedfromoneanotherbyamedianseptum.Thesurfaceareaofthecavitywallsisincreasedbyboneprojectionscalledconchae(seefig.4-1).Theconchaearecoveredbyaciliatedmucousmembranethatfilters,warms,andhumidifiestheairasitpassesthroughthenose.Olfactorycellsarelocatedintheuppermedialportionof
6、eachnasalcavity,intheliningoftheconchae.Thelacrimal(tear)glandsintheupperlateralcorneroftheorbitdrainintothenasalcavitiesbywayoftearducts.Thisiswhycryingproducesarunnynose.Theparanasalsinusesareair-filledspaceswithintheskull.Eachisnamedforthebonewherefound.Theparanasalsinusesopenintothenasalcavi
7、tiesandarealsolinedwithamucousmembrane.Inflammationofthismembraneiscalledsinusitis.Ifthepassagewaystothesinusesareblocked,apartialvacuumiscreated,caustingasinusheadache.Thenasalcavitiesareseparatedfromtheoralcavity(mouth)byt
