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1、Chapter3IntegumentarySystemAnatomyandPhysiologyoftheIntegumentarySystemIn zootomy,theintegumentarysystemistheexternalcoveringofthebody,thenamederivesfromthe Latin ‘integumentum’,whichmeans‘acovering’.Thismostextensiveorgansystemhastheskinandaccessorystructures,includinghair,nails,sweat
2、glandsandsebaceousglands.Infacttheskinisthelargestorganinthebody:12-15%ofbodyweight,withasurfaceareaof1-2meters.Theintegumentarysystemhasmultiplerolesinhomeostasis,includingprotection,sensoryreception,temperatureregulationandfluidssecretion.Theprimaryfunctionisprotectionofinternalstruc
3、tures,preventionofentryofdisease-causingmicroorganisms,itformsatwo-waybarrierthatiscapableofkeepingpathogensandharmfulchemicalsfromenteringthebody.Italsostopscriticalbodyfluidsfromescapingthebodyandpreventsinjurytotheinternalorganslyingunderneaththeskin.Thesensoryreceptorsthatdetecttem
4、perature,paintouchandpressurearelocatedintheskin.Themessagesforthesesensationsareconveyedtothespinalcordandbrainfromthenerveendingsinthemiddlelayeroftheskin.Thestructureoftheskinalsoaidsintheregulationofthebodytemperaturethroughavarietiesofmeans.Theevaporationofsweatcoolsthebody.Thebod
5、yalsolowersitsinternaltemperaturebydilatingsuperficialbloodvesselsintheskin.Thisbringsmorebloodtothesurfaceoftheskin,whichallowsthereleaseofheat.Ifthebodyneedstoconserveheat,itconstrictssuperficialbloodvesselsintheskin,keepingwarmbloodawayfromthesurfaceofthebody.Finally,thecontinuousfa
6、tlayerofthesubcutaneouslayeroftheskinactsasinsulation.Fluidsareproducedintwotypesofskinglands:sweatandsebaceous.Sweatglandsassiststhebodyinmaintainingitsinternaltemperaturebycreatingacoolingeffectwhensweatevaporates,italsoactsasamini-excretorysystem;urea,salts,andwaterarelostthroughthe
7、skinporesinsweat.Thesebaceousglands,oroilglands,produceasubstancecalledsebum.Thisoilysubstancelubricatestheskinsurface.Theskinhasotherfunctionsaswell.Forexample,theskinalsohasimportantmetabolicduties.Likelivercells,itcarriesoutsomechemicalconservationsthatactivateorinactivatecertaind
