The Circulatory System Name:_________________________________________Class:__________Date:____________

Vocabulary

• antigen• artery• atherosclerosis• blood• bloodpressure• bloodtype• capillary

• cardiovasculardisease(CVD)

• circulatorysystem• heartattack• hypertension• plasma• platelet

• pulmonarycirculation

• redbloodcell• systemic

circulation• vein• whitebloodcell

IntroductionThecirculatorysystemcanbecomparedtoasystemofinterconnected,one-wayroadsthatrangefromsuperhighwaystobackalleys.Likeanetworkofroads,thejobofthecirculatorysystemistoallowthetransportofmaterialsfromoneplacetoanother.AsdescribedinFigurebelow,thematerialscarriedbythecirculatorysystemincludehormones,oxygen,cellularwastes,andnutrientsfromdigestedfood.Transportofallthesematerialsisnecessarytomaintainhomeostasisofthebody.Themaincomponentsofthecirculatorysystemaretheheart,bloodvessels,andblood.Eachofthesecomponentsisdescribedindetailbelow.Thefunctionofthecirculatorysystemistomovematerialsaroundthebody.

The Heart Theheartisamuscularorganinthechest.Itconsistsmainlyofcardiacmuscletissueandpumpsbloodthroughbloodvesselsbyrepeated,rhythmiccontractions.Thehearthasfourchambers,asshowninFigurebelow:twoupperatria(singular,atrium)andtwolowerventricles.Valvesbetweenchamberskeepbloodflowingthroughtheheartinjustonedirection.

Thechambersoftheheartandthevalvesbetweenthemareshownhere.Blood Flow Through the Heart Bloodflowsthroughtheheartintwoseparateloops,whichareindicatedbythearrowsinthisimage.Bloodfromthelungsenterstheleftatriumoftheheart.Theleftatriumpumpsthebloodtotheleftventricle,whichpumpsittothebody.ThisloopisrepresentedbytheredarrowsinFigureabove.

Heartbeat Unlikeskeletalmuscle,cardiacmusclecontractswithoutstimulationbythenervoussystem.Instead,specializedcardiacmusclecellssendoutelectricalimpulsesthatstimulatethecontractions.Asaresult,theatriaandventriclesnormallycontractwithjusttherighttimingtokeepbloodpumpingefficientlythroughtheheart.Blood Vessels Bloodvesselsformanetworkthroughoutthebodytotransportbloodtoallthebodycells.Therearethreemajortypesofbloodvessels:arteries,veins,andcapillaries.Bloodvesselsincludearteries,veins,andcapillaries.

• Arteriesaremuscularbloodvesselsthatcarrybloodawayfromtheheart.Theyhavethickwallsthatcanwithstandthepressureofbloodbeingpumpedbytheheart.Arteriesgenerallycarryoxygen-richblood.Thelargestarteryistheaorta,whichreceivesblooddirectlyfromtheheart.

• Veinsarebloodvesselsthatcarrybloodtowardtheheart.Thisbloodisnolongerundermuchpressure,somanyveinshavevalvesthatpreventbackflowofblood.Veinsgenerallycarrydeoxygenatedblood.Thelargestveinistheinferiorvenacava,whichcarriesbloodfromthelowerbodytotheheart.

• Capillariesarethesmallesttypeofbloodvessels.Theyconnectverysmallarteriesandveins.Theexchangeofgasesandothersubstancesbetweencellsandthebloodtakesplaceacrosstheextremelythinwallsofcapillaries.Blood Vessels and Homeostasis Bloodvesselshelpregulatebodyprocessesbyeitherconstricting(becomingnarrower)ordilating(becomingwider).Theseactionsoccurinresponsetosignalsfromtheautonomicnervoussystemortheendocrinesystem.Constrictionoccurswhenthemuscularwallsofbloodvesselscontract.Thisreducestheamountofbloodthatcanflowthroughthevessels(seeFigurebelow).Dilationoccurswhenthewallsrelax.Thisincreasesbloodflowsthroughthevessels.Whenabloodvesselconstricts,lessbloodcanflowthroughit.

Constrictionanddilationallowthecirculatorysystemtochangetheamountofbloodflowingtodifferentorgans.Forexample,duringafight-or-flightresponse,dilationandconstrictionofbloodvesselsallowmorebloodtoflowtoskeletalmusclesandlesstoflowtodigestiveorgans.Dilationofbloodvesselsintheskinallowsmorebloodtoflowtothebodysurfacesothebodycanloseheat.Constrictionofthesebloodvesselshastheoppositeeffectandhelpsconservebodyheat.Blood Vessels and Blood Pressure Theforceexertedbycirculatingbloodonthewallsofbloodvesselsiscalledbloodpressure.Bloodpressureishighestinarteriesandlowestinveins.Whenyouhaveyourbloodpressurechecked,itisthebloodpressureinarteriesthatismeasured.Highbloodpressure,orhypertension,isaserioushealthriskbutcanoftenbecontrolledwithlifestylechangesormedication.Youcanlearnmoreabouthypertensionby

watchingtheanimationatthislink:http://www.healthcentral.com/high-blood-pressure/introduction-47-115.html.

Pulmonary Circulation Pulmonarycirculationisthepartofthecirculatorysystemthatcarriesbloodbetweentheheartandlungs(thetermpulmonarymeans“ofthelungs”).Itisillustratedtotheleft.Deoxygenatedbloodleavestherightventriclethroughpulmonaryarteries,whichtransportittothelungs.Inthelungs,thebloodgivesupcarbondioxideandpicksupoxygen.Theoxygenatedbloodthenreturnstotheleftatriumoftheheartthroughpulmonaryveins.Thepulmonarycirculationcarriesbloodbetweentheheartandlungs.

Systemic Circulation Systemiccirculationisthepartofthecirculatorysystemthatcarriesbloodbetweentheheartandbody.Itisillustratedtotheright.Oxygenatedbloodleavestheleftventriclethroughtheaorta.Theaortaandotherarteriestransportthebloodthroughoutthebody,whereitgivesupoxygenandpicksupcarbondioxide.Thedeoxygenatedbloodthenreturnstotherightatriumthroughveins.Thesystemiccirculationcarriesbloodbetweentheheartandbody.Cardiovascular Disease Diseasesoftheheartandbloodvessels,calledcardiovasculardiseases(CVD),areverycommon.TheleadingcauseofCVDisatherosclerosis.Atherosclerosis

Atherosclerosisisthebuildupofplaqueinsidearteries(seeFigurebelow).Plaqueconsistsofcelldebris,cholesterol,andothersubstances.Factorsthatcontributetoplaquebuildupincludeahigh-fatdietandsmoking.Asplaquebuildsup,itnarrowsthearteriesandreducesbloodflow.Thefattymaterialinsidethearteryontherightisplaque.Noticehowmuchnarrowerthearteryhasbecome.Lessbloodcanflowthroughitthanthenormalartery.Coronary Heart Disease Atherosclerosisofarteriesthatsupplytheheartmuscleiscalled

coronaryheartdisease.Thisdiseasemayormaynothavesymptomssuchaschestpain.Asthediseaseprogresses,thereisanincreasedriskofheartattack.Aheartattackoccurswhenthebloodsupplytopartoftheheartmuscleisblockedandcardiacmusclefibersdie.CoronaryheartdiseaseistheleadingcauseofdeathofadultsintheU.S.Preventing Cardiovascular DiseaseManyfactorsmayincreasetheriskofdevelopingcoronaryheartdiseaseandotherCVDs.TheriskofCVDsincreaseswithageandisgreaterinmalesthanfemalesatmostages.HavingacloserelativewithCVDalso

increasestherisk.Thesefactorscannotbecontrolled,butotherriskfactorscan,includingsmoking,lackofexercise,andhigh-fatdiet.Bymakinghealthylifestylechoices,youcanreduceyourriskofdevelopingCVD.Blood Bloodisafluidconnectivetissue.Itcirculatesthroughoutthebodythroughbloodvesselsbythepumpingactionoftheheart.Bloodinarteriescarriesoxygenandnutrientstoallthebody’scells.Bloodinveinscarriescarbondioxideandotherwastesawayfromthecellstobeexcreted.Bloodalsodefendsthebodyagainstinfection,repairsbodytissues,transportshormones,andcontrolsthebody’spH.Cellsinbloodincluderedbloodcells,whitebloodcells,andplatelets.Thetrillionsofredbloodcellsinbloodplasmacarryoxygen.Redbloodcellscontainhemoglobin,aproteinwithironthatbindswithoxygen.Bloodtypeisimportantformedicalreasons.Apersonwhoneedsabloodtransfusionmustreceivebloodthatisthesametypeashisorherown.Otherwise,thetransfusedbloodmaycauseapotentiallylife-threateningreactioninthepatient’sbloodstream.Lesson Summary

• Theheartcontractsrhythmicallytopumpbloodtothelungsandtherestofthebody.Specializedcardiacmusclecellstriggerthecontractions.

• Arteriescarrybloodawayfromtheheart,veinscarrybloodtowardtheheart,andcapillariesconnectarteriesandveins.

• Thepulmonarycirculationcarriesbloodbetweentheheartandlungs.Thesystemiccirculationcarriesbloodbetweentheheartandbody.

• Adiseasethataffectstheheartorbloodvesselsiscalledacardiovasculardisease(CVD).TheleadingcauseofCVDisatherosclerosis,orthebuildupofplaqueinsidearteries.HealthylifestylechoicescanreducetheriskofdevelopingCVD.

• Bloodisafluidconnectivetissuethatcontainsaliquidcomponentcalledplasma.Italsocontainsdissolvedsubstancesandbloodcells.Redbloodcellscarryoxygen,whitebloodcellsdefendthebody,andplateletshelpbloodclot.Lesson Review Questions Recall1.Describehowbloodflowsthroughtheheart.2.Whatcontrolsheartbeat?3.Howdoarteriesdifferfromveins?4.Whatisbloodpressure?Whatishypertension?5.Listfactorsthatincreasetheriskofcardiovasculardisease.6.Identifythreetypesofbloodcellsandtheirfunctions.ApplyConcepts7.Totakeyourpulse,youpressyourfingersagainstanarterynearthesurfaceofthebody.Whatareyoufeelingandmeasuringwhenyoutakeyourpulse?Whycan’tyoutakeyourpulsebypressingyourfingersagainstavein?8.PeoplewithtypeObloodarecalled“universaldonors”becausetheycandonatebloodtoanyoneelse,regardlessoftheirABObloodtype.Explainwhy.ThinkCritically9.Compareandcontrastthepulmonaryandsystemiccirculations.10.Explaintheroleofbloodvesselsinhomeostasis.