Andersons pediatric cardiology 70
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FIG.2.5 Multidetector-rowcomputedtomographicdatasetsegmented
andreconstructedtoshowthelocationoftheimportantmediastinal
structures.
ChambersWithintheHeart
Itisamistaketoassesstheheartinupright“valentine”fashion.1Asalready
emphasized,thecardiaclongaxisextendsfromrighttoleftwithconsiderable
obliquity(seeFig.2.1).Whenseeninfrontalprojection,theanteriorsurfaceof
thesilhouetteisoccupiedforthemostpartbytherightatriumandventricle.The
leftatriumisalmostentirelyaposteriorstructure,withonlyitsappendage
projectingtotheleftupperborder,whileonlyastripofleftventricleisseen
downtheslopingleftborder.Theso-calledrightchambersoftheheart,
therefore,arebasicallyanterior,withtheventriclessituatedtotheleftand
inferiorlyrelativetotheiratrialcounterparts.Theaorticandmitralvalvesare
closelyrelatedonetotheotherwithinthebaseoftheleftventricle,whilethe
pulmonaryandtricuspidvalvesareseparatedintheroofoftherightventricleby
theextensivesupraventricularcrest,knownclassicallyinitsLatinformasthe
cristasupraventricularis.Thecrestitselfisintimatelyrelatedonitsposterior
aspecttotheaorticroot(seeFig.2.2,left).Thediaphragmaticborderofthe
ventricularmass,madeupoftherightventricle,hasasharpanglebetweenits
sternocostalandinferiorsurfaces,knownastheacutemargin(Fig.2.6).In
contrast,theleftborderoftheventricularmassformedbytheleftventriclehasa
muchgentlercurve,andistheobtusemargin.Importantgroovesarefound
withinthevarioussurfaces,withtheatrioventricular,orcoronary,grooves
markingthecardiacshortaxis,andtheinterventriculargroovesdemonstrating
thelocationoftheventricularseptum.Aparticularlyimportantpointisfoundon
thediaphragmaticsurface,positionedinferiorlyratherthanposteriorlywhenthe
heartislocatedwithinthebody(seeFig.2.6).Thisisthecardiaccrux,which
marksthecrossingoftheinterventricularandatrioventriculargrooves.
FIG.2.6 Ventricularconephotographedfromitsapicalaspect,showingits
sternocostal,diaphragmatic,andposteriorsurfaces.Thereisanacute
anglebetweenthesternocostalanddiaphragmaticsurfaces,butanobtuse
onebetweenthesternocostalandposteriorsurfaces.Notethelocationof
theanteriorandinferiorinterventriculargrooves.Itisamistaketonamethe
inferiorgrooveasbeing“posterior.”
MorphologicallyRightAtrium
Therightatriuminthenormalheartisrecognizedmostreadilyasthechamber
receivingthesystemicvenousreturnthroughthesuperiorandinferiorcaval
veins,alongwiththevenousreturnfromtheheartitselfthroughthecoronary
sinus(Fig.2.7).
FIG.2.7 Rightatriumopened,withtheheartinattitudinallyappropriate
orientation,andviewedobliquelyfrombehind.Itshowstheatrial
components.Thereisalsoasmallbodyincorporatedbetweenthesystemic
venoussinusandtheseptum,butthisisrarelyvisiblesincetheleftvenous
valveisusuallycompletelyresorbedduringcardiacdevelopment.
Thesechannelsopenintothesmooth-walledvenouscomponentoftheatrium.
Theatrialchamberpossessesasecondsmooth-walledarea,thevestibuleofthe
tricuspidvalve.Theatriumalsohasacharacteristicseptalsurface,whichis
locatedposteriorly.Itistheappendagewithitspectinatedwallthatisthemost
prominentcomponentofthemorphologicallyrightatrium.Itformstheentirety
oftheanteriorwall(Fig.2.8).
