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Pericardium & Heart

Thorax Unit

Lecture 5 & 6 .

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Pericardium

It is a fbroserous sacenclosing heart and roots ogreat vessels. Pericardiumlies within middle

mediastinum, posterior tobody o sternum and 2nd-6thcostal cartilagesandanterior to 5th- 8th

thoracic vertebrae.

It is composed o two layers. !ibrous Pericardium

". #erous Pericardium

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Pericardium!ibrous PericardiumFibrous pericardium is

strong fbrous part o thesac. It is frmly attachedbelow to central tendon othe diaphragm. It uses with

outer coats o great bloodvessels passing through it(aorta$ %ulmonar trun'$su%erior and in(erior

venae cavae$ and%ulmonar veins). Fibrouspericardium is attached inront to sternum by

sternopericardial ligaments.

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Pericardium#erous PericardiumIt lines fbrous pericardium and coats heart. It is

divided into %arietal & visceral laers. Parietal layerlines fbrous pericardium & is reected around roots ogreat vessels to become continuous with visceral layero serous pericardium that closely covers heart.

isceral layer is callede%icardium.Pericardial cavitis a slit!li"e space between

parietal & visceral layers thatcontains a small amount otissue uid, %ericardial *uid#o acilitate heart movements

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PericardiumPericardial #inuses

#hey are recesses in pericardium cavity ormedby reection o serous pericardium on posteriorsurace o heart.

+bli,ue sinusormed around large veins.

Transverse sinus lies between

reection o serous

pericardium around

aorta and pulmonarytrun" and reection

around large veins.

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Pericardiumerve #u%%l o( Pericardium

Fibrous pericardium and parietal layer o serouspericardium are supplied by %hrenic nerves.isceral layer o the serous

pericardium is innervated by

branches o sympathetic

trun"s and vagus nerves.

H

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Hearthollow muscular & pyramid shaped organ that lies reelywithin pericardium in mediastinum and is connected at itsbase to great blood vessels.$eart has a%exand sur(aces%ex o( heart% is ormed by let ventricle, is directeddo/n/ard$ (or/ard$ and to the le(t. It lies at level othlet intercostal space, ' cm rom midline where apebeat can usually palpated in living patient.

#ur(aces o( the Heart0nterior$ 1n(erior$ Posterior

H # (

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Heart #ur(aces#ternocostal nterior) sur(ace% is ormed mainly byright atrium and right ventricle, which are separated romeach other by vertical atrioventricular groove. )ightborder is ormed by right atrium* let border, by letventricle and part o let auricle. )ight & let ventricles areseparated by anterior interventricular groove.

H t # (

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Heart #ur(aces3ia%hragmatic in(erior) sur(ace% is ormed mainly byright and let ventricles separated by posteriorinterventricular groove. Inerior surace o right atriumand inerior vena cava also orms part o this surace.

H t # (

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Heart #ur(aces"ase o( heart$ or %osterior sur(ace)% is ormedmainly by let atrium, into which open our pulmonaryveins. #he base o heart lies opposite ape.

H t

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Heart"orders o( the Heart4ight border is ormed by right atrium*le(t borderby let auricle* and below, by let ventricle.Lo/er border mainly by right ventricle but also by rightatrium*a%exis ormed by let ventricle.

h b ( th H t

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hambers o( the Heart$eart is divided by vertical septa into our chambers%right & le(t atria and right & le(t ventricles. )ightatrium lies anterior to let atrium, and right ventricle liesanterior to let ventricle.+alls o the heart are composed o cardiac muscle,mocardium* covered eternally with serouspericardium, e%icardium*and lined internally with a layer o endothelium,

endocardium.

h b ( th H t

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hambers o( the Heart4ight triumIt consists o a main cavity and a small out!pouching,auricle. #here is a vertical groove on outside o the heart at

unction between right atrium and right auricle calledsulcus terminalis, which on the inside orms a ridge calledcrista terminalis. -ain part o atrium that lies posterior tothis ridge is smooth walled and is derived embryologicallyrom sinus venosus. Part o atrium in ront o this

ridge is roughened or trabeculated bybundles o muscle fbers, musculi%ectinati, which run rom cristaterminalis to auricle. #hisanterior part is derivedembryologically rom %rimitive

atrium.

h b ( th H t

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hambers o( the Heart+%enings into the 4ight trium0#u%erior vena cava opens into upper part o rightatrium* it has no valve. It returns blood to heart romupper hal o body.1n(erior vena cava opens into lower part o right atrium*it is guarded by a rudimentary, nonunctioning valve. Itreturns blood to heart rom lower hal o the body.oronar sinus, which drains most

o blood rom the heart wall, opensinto right atrium between ineriorvena cava and atrioventricularorifce. It is guarded by a rudimentary,nonunctioning valve.

4ight trioventricular +riceliesanterior to inerior vena cavaopening and is guarded bytricus%id valve.

h b ( th H t

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hambers o( the Heart!etal 4emnants o( right atrium04udimentar valve o( in(erior vena cava!ossa ovalis & nulus ovalis0 lie on atrial septum.Fossa ovalis is a shallow depression, which is site o(oramen ovalein etus. nulus ovalis orms uppermargin o ossa.Floor o the ossa representspersistent se%tum %rimumo

heart o embryo, and anulus isormed rom lower edge ose%tum secundum.

h b ( th H t

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hambers o( the Heart4ight 7entricleIt communicates with right atrium through atrioventricularorifce and with pulmonary trun" through pulmonaryorifce. Its cavity becomes unnel shaped near pulmonaryorifce called (in(undibulum/. +alls o right ventricle aremuch thic"er thanthose o right atrium and show severalinternal proecting ridges

ormed o muscle bundlestrabeculae carneae. 0ne type othese trabeculae carneae arePa%illar muscles% whichproect inward, being attached

by their bases to ventricularwall* their apices are connectedby fbrous chords(chordae tendineae/to cusps o tricuspid valve.

h b ( th H t

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hambers o( the HeartTricus%id valveguards atrioventricular orifceand consists o 1 cusps ormed by a old oendocardium with some connective tissueenclosed%nterior$ #e%tal & 1n(erior %osterior) cus%s.2ases o cusps are attached to fbrous ring oheart s"eleton, whereas theirree edges & ventricular

suraces are attached tochordae tendineae. +henventricle contracts,papillary muscles contractand prevent cusps rom

being orced intoatrium and turning insideout as intraventricularpressure rises. hordaetendineaeo one papillarymuscle are connected toadacent parts o two cusps.

h b ( th H t

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hambers o( the HeartPulmonar valve guards pulmonary orifce and consistso 1 semilunar cusps ormed by olds o endocardium withsome connective tissue enclosed. 0pen mouths o cuspsare directed upward into pulmonary trun". o chordaeor %a%illar muscles are associated with these cusps*attachments o sides o cusps to arterialwall prevent cusps rom prolapsing intoventricle. t root o pulmonary

trun" are 1 dilatations (sinuses/each one is situated eternalto each cusp.

h b ( th H t

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hambers o( the HeartLe(t triumIt consists o a main cavity and a le(t auricle.3et atrium is situated behind right atrium andorms greater part o base (%osterior sur(ace/o heart. 2ehind it lies obli,ue sinus o serouspericardium, and fbrous pericardium separates itrom esophagus. Interior o let atrium is smooth,but let auricle possesses muscular ridges.

+%enings into the Le(t trium0!our %ulmonar veins% two romeach lung, open through posteriorwall with no valvesLe(t trioventricular +rice0 is

guarded by mitral valve.

hambers o( the Heart

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hambers o( the HeartLe(t 7entricleIt communicates with let atrium through atrioventricularorifce and with aorta through aortic orifce. +alls o letventricle are three times thic"er than those o rightventricle. In cross section, let ventricle is circular* right iscrescentic because o bulging oventricular septum into cavity o right ventricle.#here are well!developed trabeculae

carneae, two large papillary muscles.Part o ventricle below aorticorifce is called aortic vestibule..

hambers o( the Heart

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hambers o( the Heartitral valveguards atrioventricular orifce. It consists otwo cusps, one anterior and one posterior, which have astructure similar to that o tricuspid valve. nterior cusp isthe larger and intervenes between atrioventricular andaortic orifces.ortic valveguards aortic orifce and is similar topulmonary valve. 2ehind each cusp aortic wall bulges toorm an

aortic sinus. nterior aortic sinus gives originto right coronary artery, and let posteriorsinus gives origin to let coronary artery

#tructure o( the Heart

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#tructure o( the Heart9alls o( the heart0are composed o thic" layero cardiac muscle, mocardium, coveredeternally by e%icardiumand lined internally by

endocardium. tria are thin!walled and dividedby atrial interatrial) se%tum into right and letatria. entricles are thic"!walled and divided byventricularinterventricular) se%tuminto right and let ventricles.

4eptum is placed obli5uely,with one surace acingorward and to the rightand the other acingbac"ward and to the let.3ower part o septum isthic" and ormed o muscleand smaller upperpart o septum is thin& membranous andattached to fbrous

s"eleton.

#tructure o( the Heart

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#tructure o( the Heart#'eleton o( the heart0consists o fbrous rings thatsurround atrioventricular$ %ulmonar$ and aorticorices and are continuous with membranous u%%er%art o( ventricular se%tum. Fibrous rings aroundatrioventricular orifces separate muscular walls o atriarom those o ventricles but provide attachment ormuscle fbers. Fibrous rings support bases o valve cuspsand prevent valves rom stretching and becoming

incompetent. 4"eleton o heart orms basis o electricaldiscontinuity between atria and ventricles.

#tructure o( the Heart

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#tructure o( the Heartonducting #stem o( the Heart0#inuatrial ode0 is located in wall o right atrium inupper part o sulcus terminalis ust to right o opening osuperior vena cava.trioventricular ode0 is strategically placed on lowerpart o atrial septum ust above attachment o septal cuspo tricuspid valve.trioventricular "undle o( His0 It

descends through fbrous s"eletono heart behind septal cusp otricuspid valve to reach upperborder o muscular part oseptum, then divides into two

branches, one or each ventricle.4ight bundle branch 4"")Le(t bundle branch L"")#ubendocardial %lexuso( Pur'in:e bers0

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rterial #u%%l o( HeartIt is provided by right and le(t coronar arteries,which arise rom ascending aorta immediately aboveaortic valve. 6oronary arteries and their maor branchesare distributed over surace o heart, lying withinsubepicardial connective tissue.

4ight coronar arterarises rom anterioraortic sinus o ascending aorta & runs

orward between pulmonary trun" &right auricle. It descends almostvertically in right atrioventriculargroove, and at inerior border oheart it continues posteriorly along

atrioventricular groove toanastomose with let coronaryartery in posterior interventriculargroove. It supplies right atrium andright ventricle and parts o letatrium and let ventricle andatrioventricular septum.

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coronar arter0;. 4ight conus arter% supply pulmonary conus2. trial branches supply anterior and lateral suraces o

right atrium. 0ne branch supplies posterior surace o both

right and let atria. rter o( sinuatrial node suppliesnode and right and let atria* in 17 o individuals it arisesrom let coronary artery.

. 7entricular "ranches0nterior ventricular branches0supply anterior surace o

right ventricle.

arginal branch0 is the largest & runsalong lower margin o costal suraceto reach ape.Posterior ventricular branches0supply diaphragmatic suraceo right ventricle.Posterior interventriculardescending) arter0runs inposterior interventriculargroove. It supply in(erior /all &%osterior %art o( ventricular se%tum.

Large se%tal branch supplies7 node.

rterial #u%%l o( Heart

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rterial #u%%l o( HeartLe(t coronar artersupplies maor part o heart,including greater part o let atrium, let ventricle, andventricular septum. It arises rom let posterior aortic sinus

o ascending aorta and passes orward between pulmonarytrun" and let auricle. It then enters atrioventricular groove& divides into an anterior interventricular branch &circum*ex branch.nterior interventricular descending) branch0runs

downward in anterior interventricular groove. In mostindividuals it passes around ape o heartto enter posterior interventriculargroove & anastomoses withterminal branches o right coronaryartery. It supplies right & let

ventricles with numerous branchesthat also supply anterior part oventricular septum. 0ne o theseventricular branches (le(t diagonalarter/ may arise directly rom trun"

o let coronary artery. small le(tconus artersupplies pulmonary conus.

rterial #u%%l o( Heart

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rterial #u%%l o( Heartircum*ex arter0 same si8e as anterior interventricularartery. It winds around let margin o heart in atrioventriculargroove.

Le(t marginal arteris a large branch supplying let margin olet ventricle down to ape.nterior & %osterior ventricular branches supply letventricle.trial branches supply let atrium.

oronar rter nastomosesbetween terminalbranches o right & let coronaryarteries eist, but not large toprovide an ade5uate bloodsupply to cardiac muscle i oneo large branches becomesbloc"ed. sudden bloc" o oneo larger branches o eithercoronary artery usually leadsto mocardial in(arction, althoughsometimes collateral circulation isenough to sustain muscle.

rterial #u%%l o( Heart

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rterial #u%%l o( Heart7ariations in the oronar rteriesariations in blood supply to heart do occur, and mostcommon variations a9ect blood supply to diaphragmatic

surace o both ventricles. $ere origin, si8e, anddistribution o posterior interventricular artery arevariable.

1n right dominance, posterior

interventricular artery is a large brancho right coronary artery. )ightdominance is present inmost individuals (':7/.

1n le(t dominance, posteriorinterventricular artery is abranch o circume brancho let coronary artery (;:7/.

H t

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Heart-ost blood rom heart wall drains into right atriumthrough coronar sinus, which lies in posterior part oatrioventricular groove and is a continuation o great

cardiac vein. It opens into right atrium to let o ineriorvena cava. #mall and middle cardiac veinsaretributaries o coronary sinus.)emainder o blood is returned to rightatrium by anterior cardiac vein and by

small veins that open directly intoheart chambers.

erve #u%%l o( Heart

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erve #u%%l o( Heart$eart is innervated by sympathetic and parasympatheticfbers o autonomic nervous system via cardiac%lexuses situated below arch o aorta. 4ympathetic

supply arises rom cervical & upper thoracic portions osympathetic trun"s, and parasympathetic supply comesrom vagus nerves.#m%athetic bers terminate on 4 & nodes,cardiac muscle fbers & coronary arteries. #hese nerves

results incardiac acceleration, increased contractiono cardiac muscle, and dilatation ocoronary arteries.Parasm%athetic bers terminate on

4 & nodes and on coronaryarteries. #hese fbers resultsin a reduction in rate and orce ocontraction o heart and aconstriction o coronary arteries.

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Than'