Heart enclosed within Heart enclosed within the pericardial sac is the pericardial sac is located in the located in the middle middle mediastinummediastinum

MediastinumMediastinumThe The cavity of thorax cavity of thorax is divided into:is divided into:• A median partition, the A median partition, the

mediastinummediastinum• Laterally placed Laterally placed pleurae & lungspleurae & lungs

Mediastinum is a Mediastinum is a thick mobile thick mobile partition, partition, formed by the structures formed by the structures occupying the occupying the central part of the central part of the thoracic cavitythoracic cavity, between the lungs, between the lungs

It extends:It extends:• SuperiorlySuperiorly to the to the thoracic inletthoracic inlet & &

the the root of neckroot of neck• InferiorlyInferiorly to the to the diaphragmdiaphragm• AnteriorlyAnteriorly to the to the sternumsternum• PosteriorlyPosteriorly to the to the twelve thoracic twelve thoracic

vertebraevertebrae

Mediastinum: DivisionsMediastinum: DivisionsDivided, by an imaginary Divided, by an imaginary plane passing from the plane passing from the sternal anglesternal angle anteriorly to anteriorly to the the lower border of the body lower border of the body of the 4of the 4thth thoracic thoracic vertebravertebra posteriorly, into: posteriorly, into: • Superior Superior mmediastinumediastinum• InferiorInferior mediastinummediastinum

The inferior mediastinum is The inferior mediastinum is further divided into:further divided into:• AnteriorAnterior• MiddleMiddle• PosteriorPosterior

PericardiumPericardiumDouble layered fibroserousDouble layered fibroserous sac that encloses the sac that encloses the heart & heart & the roots of the great vesselsthe roots of the great vesselsLocated in the Located in the middle middle mediastinummediastinum Posterior to the Posterior to the body of body of

sternum and 2nd-6sternum and 2nd-6thth costal costal cartilagescartilages

Anterior to Anterior to T5-T8 T5-T8 vertebraevertebrae

1-1.5 cm to the right 1-1.5 cm to the right of the of the sternumsternum

5-7.5 cm to the left 5-7.5 cm to the left of of median plane at the level median plane at the level of of 55thth intercostal space intercostal space

Pericardium cont’dPericardium cont’d

The strong outer layer, The strong outer layer, the the fibrous pericardium fibrous pericardium is composed of tough is composed of tough fibrous tissuefibrous tissue

The inner transparent The inner transparent membrane, the membrane, the serous serous pericardiumpericardium, has two , has two layers:layers:• ParietalParietal• VisceralVisceral

Fibrous PericardiumFibrous Pericardium

Tough Tough conicalconical outer outer fibrous sac, protects heart fibrous sac, protects heart against sudden overfillingagainst sudden overfillingSuperiorly:Superiorly: Pierced by Pierced by aortaaorta, ,

pulmonary trunkpulmonary trunk, and , and superior vena cavasuperior vena cava

Becomes fused with the Becomes fused with the tunica adventitia of tunica adventitia of these vesselsthese vessels

Below:Below: rests on and is rests on and is fused with the fused with the central central tendon of the diaphragmtendon of the diaphragm

Fibrous Pericardium cont’dFibrous Pericardium cont’dAnteriorlyAnteriorly attached to the attached to the posterior surface of posterior surface of sternum by sternum by condensations of condensations of connective tissue called connective tissue called the the sternopericardial sternopericardial ligamentsligamentsPosteriorly:Posteriorly: Pierced by Pierced by pulmonary pulmonary

veins veins andand inferior vena inferior vena cavacava

Becomes fused with Becomes fused with the tunica adventitia of the tunica adventitia of these vesselsthese vessels

Serous PericardiumSerous PericardiumParietal layer Parietal layer lines the fibrous lines the fibrous pericardium and becomes pericardium and becomes continuous with the visceral layer continuous with the visceral layer around the roots of great vesselsaround the roots of great vessels

Visceral layer Visceral layer reflected onto the reflected onto the heart, forms the external layer of heart, forms the external layer of the heart wall (the heart wall (epicardiumepicardium))

The two layers are continuous The two layers are continuous with each other at the base of the with each other at the base of the large vesselslarge vessels

Pericardial cavity Pericardial cavity lies between the lies between the two layers, that contains a thin film two layers, that contains a thin film of serous fluid which helps in of serous fluid which helps in frictionless movement of the heartfrictionless movement of the heart

Pericardial SinusesPericardial SinusesDevelop during folding of Develop during folding of embryonic heartembryonic heart

Transverse sinus:Transverse sinus: Lies posterior to ascending aorta and Lies posterior to ascending aorta and

pulmonary trunk, anterior to superior pulmonary trunk, anterior to superior vena cavavena cava

Communicates with the main part of Communicates with the main part of pericardial cavity at its right and left pericardial cavity at its right and left endsends

Oblique sinus:Oblique sinus: An inverted U-shaped blind recess An inverted U-shaped blind recess

lies posterior to the heart extending lies posterior to the heart extending posterior to the left atrium, can be posterior to the left atrium, can be entered inferiorlyentered inferiorly

Produced by the reflection of Produced by the reflection of pericardium onto the pulmonary veins pericardium onto the pulmonary veins and inferior vena cava and inferior vena cava

Blood SupplyBlood SupplyArterial Supply: Arterial Supply: • Fibrous pericardium & the parietal layerFibrous pericardium & the parietal layer of the of the

serous pericardium serous pericardium : Mainly supplied by : Mainly supplied by pericardiophrenicpericardiophrenic and and musculophrenicmusculophrenic arteries, arteries, branches of internal thoracic. Also supplied by branches of internal thoracic. Also supplied by pericardial branches of pericardial branches of bronchialbronchial, , esophageal esophageal and and superior phrenic superior phrenic arteriesarteries

• Visceral layer of the serous pericardium Visceral layer of the serous pericardium (epicardium) supplied by the branches of the (epicardium) supplied by the branches of the coronarycoronary arteriesarteries

Venous drainage:Venous drainage: Veins are tributaries of Veins are tributaries of azygos azygos systemsystem. Pericardiophrenic veins also drain into the . Pericardiophrenic veins also drain into the internal thoracic vein internal thoracic vein

Nerve SupplyNerve Supply

The The fibrous pericardiumfibrous pericardium and the and the parietal parietal layer of the serous pericardiumlayer of the serous pericardium are supplied are supplied by the by the phrenic nervesphrenic nerves. .

The The visceral layer of the serous pericardiumvisceral layer of the serous pericardium is innervated by is innervated by sympathetic & sympathetic & parasympathetic parasympathetic fibersfibers through the through the sympathetic trunks sympathetic trunks and the and the vagus nerves vagus nerves respectivelyrespectively

Clinical NotesClinical Notes

Pericarditis & pericardial effusionPericarditis & pericardial effusion

Cardiac temponadeCardiac temponade

Friction rubFriction rub

PericardiocentesisPericardiocentesis: A wide-bore needle : A wide-bore needle may be inserted through the left 5may be inserted through the left 5thth & 6 & 6thth intercostal space near the sternum (area intercostal space near the sternum (area of cardiac notch). of cardiac notch). Intracardial injectionsIntracardial injections are also given through this areaare also given through this area

To be handled with care….

HeartHeartHollow muscular Hollow muscular organ, acts as a organ, acts as a double pumpdouble pump

Conical in shapeConical in shape

Slightly larger than the Slightly larger than the clenched fistclenched fist

Lies free within the Lies free within the pericardiumpericardium

Connected superiorly Connected superiorly to the large vesselsto the large vessels

Heart cont’dHeart cont’dHas Has 4 chambers4 chambers: : two atriatwo atria superiorly and superiorly and two ventriclestwo ventricles inferiorly, separated from inferiorly, separated from each other by each other by atrioventricularatrioventricular and and interventricularinterventricular grooves grooves

Atria act as the Atria act as the receiving receiving chamberschambers and the ventricles and the ventricles as the as the pumping chamberspumping chambers

Right side Right side of the heart of the heart contains contains deoxygenated deoxygenated blood blood & & left sideleft side contains contains oxygenated bloodoxygenated blood

External Features: SurfacesExternal Features: Surfaces

The heart has:The heart has:SternocostalSternocostal (Anterior) surface (Anterior) surfaceDiaphragmaticDiaphragmatic (Inferior) surface (Inferior) surfaceBaseBase (Posterior surface) (Posterior surface)ApexApex

Sternocostal SurfaceSternocostal SurfaceFormed mainly by Formed mainly by the the right atriumright atrium and and the the right ventricleright ventricle separated by vertical separated by vertical atrioventricular atrioventricular groovegrooveThe The anterior anterior interventricular interventricular groovegroove separates separates the right ventricle the right ventricle from the left from the left ventricleventricle

Diaphragmatic SurfaceDiaphragmatic Surface

Formed mainly by Formed mainly by the the right right and and left left ventriclesventricles separated separated by posterior by posterior interventricular interventricular groovegroove, and a small , and a small part of the part of the right right atrium,atrium, into which the into which the inferior vena cava inferior vena cava opensopens

Base (Posterior Surface)Base (Posterior Surface)

Formed mainly by the Formed mainly by the left atriumleft atrium, into which , into which open the 4 pulmonary open the 4 pulmonary veinsveins

Quadrilateral in shapeQuadrilateral in shape

Lies opposite the apexLies opposite the apex

Faces Faces posteriorly, posteriorly, superiorly and toward superiorly and toward the right shoulderthe right shoulder

ApexApexFormed by Formed by left ventricleleft ventricle

Directed Directed downward, forward downward, forward and to the leftand to the left

Located posterior to the left Located posterior to the left 55thth intercostal spaceintercostal space, , 7-9 cm from 7-9 cm from the median planethe median plane and just and just medial to the left midclavicular medial to the left midclavicular lineline

Position varies slightly with the Position varies slightly with the person’s position and the phase person’s position and the phase of respirationof respiration

Is the point of maximal Is the point of maximal pulsation of the heart (the pulsation of the heart (the apex apex beatbeat can be seen as well as can be seen as well as palpated)palpated)

Borders of the HeartBorders of the HeartThe heart has The heart has 4 borders4 borders:: RightRight: Formed by the : Formed by the right right

atriumatrium LeftLeft: Formed by the : Formed by the left auricleleft auricle

above and the above and the left ventricleleft ventricle belowbelow

InferiorInferior: Formed mainly by the : Formed mainly by the right ventricleright ventricle, and the , and the apex of apex of the left ventricle the left ventricle

SuperiorSuperior border is where great border is where great vessels enter or leave the heart. vessels enter or leave the heart. Formed by Formed by right and left auriclesright and left auricles and and superior part of right & left superior part of right & left ventricleventricle

Surface Projection of the Heart

Blood Supply of the HeartBlood Supply of the Heart

Arterial SupplyArterial SupplySupplied by right & left Supplied by right & left coronary arteriescoronary arteries

Coronary arteries arise Coronary arteries arise from the from the ascending aortaascending aorta immediately above the immediately above the aortic valvesaortic valves

Coronary arteries and their Coronary arteries and their branches are distributed branches are distributed over the surface of the over the surface of the heart lying within the heart lying within the subepicardial connective subepicardial connective tissuetissue

Right Coronary ArteryRight Coronary ArteryArises from Arises from anterior sinus anterior sinus of ascending aortaof ascending aortaRuns between the Runs between the pulmonary trunk and right pulmonary trunk and right auricleauricleRuns in the atrioventricular Runs in the atrioventricular groovegrooveAt the inferior border of the At the inferior border of the heart turns posteriorly in heart turns posteriorly in the atrioventricular groovethe atrioventricular grooveAnastomoses with the left Anastomoses with the left coronary artery in the coronary artery in the posterior interventricular posterior interventricular groovegroove

Right Coronary Artery: BranchesRight Coronary Artery: BranchesRight conus arteryRight conus arteryAnterior ventricular Anterior ventricular branchesbranches: 2-3 in number, : 2-3 in number, largest is the marginal largest is the marginal branchbranchPosterior ventricular Posterior ventricular branchesbranches, gives a branch , gives a branch to to atrioventricular nodeatrioventricular nodePosterior interventricular Posterior interventricular arteryarteryAtrial branchesAtrial branches, & artery of , & artery of the the sinuatrial node sinuatrial node which which also supplies atriaalso supplies atria

Left Coronary ArteryLeft Coronary ArteryLarger than the rightLarger than the rightSupplies major part of the Supplies major part of the heartheartArises from Arises from the left the left posterior aortic sinusposterior aortic sinusRuns between the Runs between the pulmonary trunk and left pulmonary trunk and left auricleauricleRuns in the Runs in the atrioventricular groove atrioventricular groove Divides into anterior Divides into anterior interventricular & interventricular & circumflex branchescircumflex branches

Left Coronary Artery: BranchesLeft Coronary Artery: Branches

Anterior interventricular Anterior interventricular arteryartery, gives a small , gives a small conus arteryconus artery

Circumflex arteryCircumflex artery, gives:, gives:

Left marginalLeft marginal

Anterior ventricularAnterior ventricular

Posterior ventricularPosterior ventricular

Atrial branchesAtrial branches

Variations in Coronary ArteriesVariations in Coronary ArteriesIn 35% of individuals, the In 35% of individuals, the sinuatrial artery sinuatrial artery arises arises from from left coronary arteryleft coronary arteryIn most of the individuals In most of the individuals (90%), the posterior (90%), the posterior interventricular artery is a interventricular artery is a branch of right coronary branch of right coronary artery (artery (Right Right DominanceDominance). In 10% of ). In 10% of the individuals, it arises the individuals, it arises from circumflex branch of from circumflex branch of left coronary artery (left coronary artery (Left Left DominanceDominance))

Coronary Artery AnastomosesCoronary Artery Anastomoses

Though anastomoses do exist between Though anastomoses do exist between the terminal branches of the right and left the terminal branches of the right and left coronary arteries, but these are not large coronary arteries, but these are not large enough to compensate for any sudden enough to compensate for any sudden blockage of a large branch.blockage of a large branch.

A sudden blockage of the larger branches A sudden blockage of the larger branches results in results in myocardial infarction. myocardial infarction.

Venous DrainageVenous DrainageMost of the blood drains into the Most of the blood drains into the right atrium through the right atrium through the coronary coronary sinus, sinus, which:which:

Lies in the posterior part of the Lies in the posterior part of the atrioventricular sulcusatrioventricular sulcus

Is continuation of the great cardiac Is continuation of the great cardiac veinvein

Opens into the right atrium to the Opens into the right atrium to the left of the inferior vena cavaleft of the inferior vena cava

TributariesTributaries: : Small cardiac veinSmall cardiac vein Middle cardiac veinMiddle cardiac vein Posterior vein of the left ventriclePosterior vein of the left ventricle Oblique vein of the left atriumOblique vein of the left atrium

Venous Drainage cont’dVenous Drainage cont’d

Anterior cardiac veinsAnterior cardiac veins drain directly into the drain directly into the right atriumright atriumVena cordis minimiVena cordis minimi (Thebesian veins) (Thebesian veins) open directly into open directly into heart chambersheart chambers

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