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THEHEART
THEHEART
•  MEDIASTINUM
•  PERICARDIUM
•  HEART
THEHEART
THEMEDIASTINUM
Themedias5numoccupiedbythemassof2ssuebetweenthetwo
pulmonarycavi2es,isthecentralcompartmentofthethoraciccavity.
Themedias2numisaninterpleuralspaceandconsistsofthesuperior
medias2numandinferiormedias2num,whichdividesintothe
anterior,middle,andposteriormedias2na.
THESUPERIORMEDIASTINUM
THEHEART
Thesuperiormedias5numcontainstheSVC,brachiocephalicveins,
archoftheaorta,thoracicduct,trachea,esophagus,thymus,vagus,
leBrecurrentlaryngeal,andphrenicnerves.
Thesuperiorvenacava(SVC)returnsbloodfromallstructures
superiortothediaphragm,exceptthelungsandheart.
Thearchoftheaorta(aor5carch),thecurvedcon2nua2onofthe
ascendingaorta.
Thearchoftheazygosveinoccupiesaposi2oncorrespondingtothe
aortaontherightsideofthetracheaovertherootoftherightlung,
althoughthebloodisflowingintheoppositedirec2on.The
ligamentumarteriosum,theremnantofthefetalductusarteriosus,
passesfromtherootoftheleBpulmonaryarterytotheinferior
surfaceofthearchoftheaorta.
Thebrachiocephalictrunk,thefirstandlargestbranchofthearchof
theaorta,arisesposteriortothemanubrium,whereitisanteriorto
thetracheaandposteriortotheleBbrachiocephalicvein.
THESUPERIORMEDIASTINUM
THEHEART
TheleJcommoncaro5dartery,thesecondbranchofthearchofthe
aorta,arisesposteriortothemanubrium,slightlyposteriorandtothe
leBofthebrachiocephalictrunk.
TheleJsubclavianartery,thethirdbranchofthearchoftheaorta,
arisesfromtheposteriorpartofthearch,justposteriortotheleB
commoncaro2dartery.
Therightvagusnerve(RVN)entersthethoraxanteriortotheright
subclavianartery,whereitgivesrisetotherightrecurrentlaryngeal
nerve.
TheleJvagusnerve(LVN)descendsintheneckposteriortotheleB
commoncaro2dartery
THESUPERIORMEDIASTINUM
THEHEART
TheleJvagusnerve(LVN)isseparatedlaterallyfromthephrenic
nervebytheleBsuperiorintercostalvein.
AstheLVNcurvesmediallyattheinferiorborderofthearchofthe
aorta,itgivesofftheleJrecurrentlaryngealnerve.
TheleBrecurrentlaryngealnervepassesinferiortothearchofthe
aorta,immediatelylateraltotheligamentumarteriosum,andascends
tothelarynxinthegroovebetweenthetracheaandtheesophagus.
THEANTERIORMEDIASTINUM
THEHEART
Theanteriormedias5numcontainstheremnantsofthethymusgland,
lymphnodes,andfat.
THEMIDDLEMEDIASTINUM
Themiddlemedias5numcontainsthe
•  heart,
•  pericardium,
•  phrenicnerves,
•  rootsofthegreatvessels,
•  archoftheazygosvein,and
•  mainbronchi.
THEHEART
THEPOSTERIORMEDIASTINUM
Theposteriormedias5numcontainsthe
•  esophagus,
•  thoracicaorta,
•  azygosandhemiazygosveins,
•  thoracicduct,
•  vagusnerves,
•  sympathe2ctrunks,
•  splanchnicnerves.
THEHEART
THEPERICARDIUM
THEHEART
Themiddlemedias5numincludesthepericardium,heart,androots
ofitsgreatvessels:
•  ascendingaorta,
•  pulmonarytrunk,
•  SVC.
Thepericardiumisafibroserousmembranethatcovers:
•  theheartand
•  thebeginningofitsgreatvessels.
Thetoughexternallayer,thefibrouspericardium,iscon2nuouswith
thecentraltendonofthediaphragm.
THEPERICARDIUM
THEHEART
Theinternalsurfaceofthefibrouspericardiumislinedwitha
glisteningserousmembrane,theparietallayerofserouspericardium.
Theparietallayerofserouspericardiumisreflectedontotheheartat
thegreatvessels(aorta,pulmonarytrunkandveins,andsuperiorand
inferiorvenaecavae)astheviscerallayerofserouspericardium.
THEPERICARDIUM
THEHEART
Thefibrouspericardiumis:
•  con2nuoussuperiorlywiththetunicaadven55aofthegreat
vesselsenteringandleavingtheheartandwiththepretracheal
layerofdeepcervicalfascia.
•  aOachedanteriorlytotheposteriorsurfaceofthesternumbythe
sternopericardialligaments,whicharehighlyvariableintheir
development.
•  boundposteriorlybylooseconnec2ve2ssuetostructuresinthe
posteriormedias2num.
•  con2nuousinferiorlywiththecentraltendonofthediaphragm
THEPERICARDIUM
THEHEART
Theinferiorwall(floor)ofthefibrouspericardialsacisfirmly
aOachedandconfluent(par2allyblended)centrallywiththe
centraltendonofthediaphragm-thepericardiacophrenicligament.
Thepericardiumisinfluencedbymovementsoftheheartandgreat
vessels,thesternum,andthediaphragm.
THEPERICARDIUM
THEHEART
Thepericardialcavityisthepoten5alspacebetweenopposinglayers
oftheparietalandviscerallayersofserouspericardium.Itnormally
containsathinfilmoffluidthatenablesthehearttomoveandbeatin
afric2onlessenvironment.
Theviscerallayerofserouspericardiumformstheepicardium,the
outermostofthreelayersoftheheartwall.
Thetransversepericardialsinusisatransverselyrunning
passagewithinthepericardialcavitybetweenthesetwogroups
ofvesselsandthereflec2onsofserouspericardiumaround
them.
THEPERICARDIUM
THEHEART
Apericardialreflec2onsurroundingtheveinsoftheheartformsthe
obliquepericardialsinus,awidepocket-likerecessinthepericardial
cavityposteriortothebase(posterioraspect)oftheheart,formedby
theleJatrium
Thearterialsupplyofthepericardiumismainlyfromaslenderbranch
oftheinternalthoracicartery,thepericardiacophrenicartery.
THEPERICARDIUM
THEHEART
Thenervesupplyofthepericardiumisfromthe:
•  Phrenicnerves(C3–C5),primarysourceofsensoryfibers;pain
sensa2onsconveyedbythesenervesarecommonlyreferredtothe
skin(C3–C5dermatomes)oftheipsilateralsupraclavicularregion
(topoftheshoulderofthesameside).
•  Vagusnerves,func2onuncertain.
•  Sympathe5ctrunks,vasomotor.
THEPERICARDIUM
TheFunc5onofthePericardium:
•  Protectsandanchorstheheart
•  Preventsoverfillingoftheheartwithblood
•  Allowsforthehearttoworkinarela2velyfric2on-free
environment
THEHEART
THEHEART
THEHEART
•  Centerofthecardiovascularsystem,theheart.
•  Connectstobloodvesselsthattransportbloodbetweenthe
heartandotherbody2ssues.
•  arteriescarrybloodawayfromtheheart
•  veinscarrybloodbacktotheheart
•  Arteriescarrybloodhighinoxygen.
•  (exceptforthepulmonaryarteries)
•  Veinscarrybloodlowinoxygen.
•  (exceptforthepulmonaryveins)
•  Arteriesandveinsenteringandleavingtheheartarecalledthe
greatvessels
THEHEART
THEHEART
•  Ensurestheunidirec5onalflowofbloodthroughboththeheart
andthebloodvessels.
•  Backflowofbloodispreventedbyvalveswithintheheart.
•  Actsliketwoindependent,side-by-sidepumpsthatwork
independentlybutatthesamerate.(doublecircuit)
•  onedirectsbloodtothelungsforgasexchange
•  theotherdirectsbloodtobody5ssuesfornutrientdelivery
THEHEART
Vesselsreturningbloodtotheheartinclude:
1.  Superiorandinferiorvenaecavae
2.  RightandleBpulmonaryveins
THEHEART
THEHEART
Vesselsconveyingbloodawayfromtheheartinclude:
1.  Pulmonarytrunk,whichsplitsintorightandleB
pulmonaryarteries
2.  Ascendingaorta(threebranches)–
a.  Brachiocephalic
b.  LeBcommoncaro2d
c.  Subclavianarteries
THEHEART
THEHEART
Vesselsreturningbloodtotheheartinclude:
1.  Superiorandinferiorvenaecavae
2.  RightandleBpulmonaryveins
Vesselsconveyingbloodawayfromtheheartinclude:
1.  Pulmonarytrunk,whichsplitsintorightandleB
pulmonaryarteries
2.  Ascendingaorta(threebranches)–
a.  Brachiocephalic
b.  LeBcommoncaro2d
c.  Subclavianarteries
THEHEART
ATRIAOFTHEHEART
THEHEART
•  Atriaarethereceivingchambersoftheheart
•  Eachatriumhasaprotrudingauricle
•  Pec5natemuscleslocatedwithintheanteriorwalloftheright
atrium
•  Bloodentersrightatriafromsuperiorandinferiorvenaecavae
andcoronarysinus
•  BloodentersleJatriafrompulmonaryveins
VENTRICULESOFTHEHEART
•  Ventriclesarethedischargingchambersoftheheart
•  Papillarymusclesandtrabeculaecarneaemusclesmark
ventricularwalls
•  Rightventriclepumpsbloodintothepulmonarytrunk
•  LeJventriclepumpsbloodintotheaorta
•  MyocardiumofleJventricleismuchthickerthantheright.
THEHEART
THEHEART
PATHWAYOFBLOOD
THROUGHTHEHEART
ANDLUNGS
•  Rightatriumàtricuspidvalveà
rightventricle
•  Rightventricleàpulmonary
semilunarvalveàpulmonary
arteriesàlungs
•  LungsàpulmonaryveinsàleB
atrium
•  LeBatriumàbicuspidvalveà
leBventricle
•  LeBventricleàaor5csemilunar
valveàaorta
•  Aortaàsystemiccircula2on
THEHEART
THEHEART
Therightsideoftheheart(rightheart)receivespoorlyoxygenated
(venous)bloodfromthebodythroughtheSVCandIVCandpumpsit
throughthepulmonarytrunkandarteriestothelungsfor
oxygena2on.
TheleJsideoftheheart(leJheart)receiveswell-oxygenated
(arterial)bloodfromthelungsthroughthepulmonaryveinsand
pumpsitintotheaortafordistribu2ontothebody.
THEHEART
THEHEART
Thehearthasfourchambers:
•  rightandleBatria
•  rightandleBventricles.
Theatriaarereceivingchambersthatpumpbloodintotheventricles
(thedischargingchambers).
Thewallofeachheartchamberconsistsofthreelayers,
fromsuperficialtodeep:
1.Endocardium
2.Myocardium
3.Epicardium
THEHEART
THEHEART
Thewallofeachheartchamberconsistsofthreelayers,
fromsuperficialtodeep:
1.Endocardium,athininternallayer(endotheliumand
subendothelialconnec2ve2ssue)orliningmembraneoftheheart
thatalsocoversitsvalves.
2.Myocardium,athick,helicalmiddlelayercomposedofcardiac
muscle.
3.Epicardium,athinexternallayer(mesothelium)formedbythe
viscerallayerofserouspericardium.
Thecardiacmusclefibersareanchoredtothefibrousskeletonofthe
heart.
THEHEART
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THEHEART
theapexoftheheart
thebaseoftheheart
right(acute)border
leB(obtuse)border
Theapexoftheheartisthebluntroundedextremityoftheheart
formedbytheleBventricleandliesintheleJfiJhintercostalspace
slightlymedialtothemidclavicularline.Thisloca2onisusefulclinically
fordeterminingtheleBborderoftheheartandforausculta2ngthe
mitralvalve.
Itsposterioraspect,calledthebase,isformedprimarilybytheleB
atriumandonlypartlybytheposteriorrightatrium.
THEHEART
THEHEART
Itsright(acute)borderisformedby:
theSVC,rightatrium,andIVC.
ItsleJ(obtuse)borderisformedbytheleBventricle.(Inradiology,
thele1borderconsistsoftheaor6carch,pulmonarytrunk,le1auricle,
andle1ventricle.)
THEHEART
Thefoursurfacesoftheheartarethe:
1.Anterior(sternocostal)surface
2.Diaphragma2c(inferior)surface
3.Rightpulmonarysurface
4.LeBpulmonarysurface
THEHEART
THEHEART
THEHEART
Thefoursurfacesoftheheartarethe:
1.Anterior(sternocostal)surface,formedmainlybythe
rightventricle.
2.Diaphragma5c(inferior)surface,formedmainlybytheleBventricle
andpartlybytherightventricle;itisrelatedmainlytothecentral
tendonofthediaphragm.
3.Rightpulmonarysurface,formedmainlybytheright
atrium.
4.LeJpulmonarysurface,formedmainlybytheleBventricle;
itformsthecardiacimpressionintheleBlung.
THERIGHTATRIUM
THEHEART
Therightatriumformstherightborderoftheheartandreceives
venousbloodfromtheSVC,IVC,andcoronarysinus.
Theear-likerightauricleisaconicalmuscularpouchthatprojects
fromthischamberlikeanadd-onroom,increasingthecapacityofthe
atriumasitoverlapstheascendingaorta.
Theopeningofthecoronarysinus,ashortvenoustrunkreceiving
mostofthecardiacveins,isbetweentherightAVorificeandtheIVC
orifice.
Theinteratrialseptumsepara2ngtheatriahasanoval,thumbprintsizedepression,theovalfossa,whichisaremnantoftheoval
foramenanditsvalveinthefetus.
THERIGHTVENTRICLE
THEHEART
Therightventricleformsthelargestpartoftheanteriorsurface
oftheheart.
Theinflowpartoftheventriclereceivesbloodfromtherightatrium
throughtherightAV(tricuspid)orifice
TendinouscordsaOachtothefreeedgesandventricular
surfacesoftheanterior,posterior,andseptalcusps,muchlikethe
cordsaOachingtoaparachute.
Thetendinouscordsarisefromtheapicesofpapillarymuscles
Theinflowpartoftherightventricleisseparatedfromtheou]lowpart
bythesupraventricularcrest.
THERIGHTVENTRICLE
THEHEART
Threepapillarymusclesintherightventriclecorrespondtothecusps
ofthetricuspidvalve:
•  anteriorpapillarymuscle
•  posteriorpapillarymuscle
•  septalpapillarymuscle
THELEFTATRIUM
THEHEART
TheleJatriumformsmostofthebaseoftheheart
ThemuscularleJauricleformsthesuperiorpartoftheleBborderof
theheartandoverlapstherootofthepulmonarytrunk
Fourpulmonaryveins(twosuperiorandtwoinferior)enteringits
smoothposteriorwall
THELEFTVENTRICLE
THEHEART
TheleJventricleformstheapexoftheheart,nearlyallitsleB
(pulmonary)surfaceandborder,andmostofthediaphragma5c
surface.
Wallsthataretwotothree5mesasthickasthoseoftherightventricle
Adouble-leafletmitralvalvethatguardstheleBAVorifice
Themitralvalvehastwocusps,anteriorandposterior.
Anaor5corificethatliesinitsrightposterosuperiorpart
TendinouscordintheleBventriclearisefromtheapicesofthe
anteriorandposteriorpapillarymuscles
THESEMILUNARVALVES
THEHEART
Eachofthreesemilunarcuspsofthepulmonaryvalve(anterior,right,
leB),likethesemilunarcuspsoftheaor5cvalve(posterior,right,leB),
isconcavewhenviewedsuperiorly
THEVASCULATUREOFHEART
THEHEART
Thebloodvesselsoftheheartcomprisethecoronaryarteriesand
cardiacveins,whichcarrybloodtoandfrommostofthemyocardium
Thecoronaryarteries,thefirstbranchesoftheaorta,supplythe
myocardiumandepicardium.
Thecoronaryarteriessupplyboththeatriaandtheventricles
Therightcoronaryartery(RCA)arisesfromtherightaor2csinusofthe
ascendingaorta.
TheleJcoronaryartery(LCA)arisesfromtheleBaor2c
sinusoftheascendingaorta
Theheartisdrainedmainlybyveinsthatemptyintothecoronarysinus
andpartlybysmallveinsthatemptyintotherightatrium
REGULATINGSYSTEMSOFHEART
THEHEART
Theconduc5ngsystemoftheheartgeneratesandtransmitsthe
impulsesthatproducethecoordinatedcontrac2onsofthecardiac
cycle
Thesinu-atrial(SA)nodeislocatedanterolaterallyjustdeeptothe
epicardiumatthejunc2onoftheSVCandrightatrium.TheSAnodeis
suppliedbythesinu-atrialnodalartery,whichusuallyarisesasanatrial
branchoftheRCA(in60%ofpeople),butitoBenarisesfromtheLCA
(in40%).
REGULATINGSYSTEMSOFHEART
THEHEART
Theatrioventricular(AV)nodeisasmallercollec2onofnodal2ssue
thantheSAnode.TheAVnodedistributesthesignaltotheventricles
throughtheAVbundle.TheAVbundledividesintorightandleB
bundles,proceedoneachsideofthemuscularIVSdeeptothe
endocardiumandthenramifyintosubendocardialbranches(Purkinje
fibers).
Theatrioventricular(AV)islocatedintheposteroinferiorregionofthe
interatrialseptumneartheopeningofthecoronarysinus.
THEHEART
THEHEART
Thesynchronouspumpingac2onsoftheheart’stwoatrioventricular
(AV)pumps(rightandleBchambers)cons2tutethecardiaccycle.
Thecyclebeginswithaperiodofventricularelonga2onandfilling
(diastole)andendswithaperiodofventricularshortening
andemptying(systole).
CARDIALCYCLE
THEHEART
Theinclusiveperiodof2mefromthestartofoneheartbeattothe
ini5a5onofthenext.
Allchamberswithintheheartexperiencealternateperiodsof
contrac5onandrelaxa5on.
Contrac5onofaheartchamberiscalledsystole.
•  forcesbloodintoanotherchamber(fromatriumtoventricle)
•  forcesbloodintoabloodvessel(fromaventricleintothe
aOachedlargeartery)
Relaxa5onphaseofaheartchamberistermeddiastole.
•  myocardiumofeachchamberrelaxesbetweencontrac2on
phases
•  andthechamberfillswithblood
THEHEART
THEHEART
Twoheartsoundsareheardwithastethoscope:
LUB(1st)soundasthebloodistransferredfromtheatriaintothe
ventricles,
DUB(2nd)soundastheventriclesexpelbloodfromtheheart.