HEART ANATOMY

DR. EMAD ABU ALRUB

AAUJ

HEART ANATOMYApproximately the size of your fistWt. = 250-300 gramsLocationIn the mediastinum between the lungsSuperior surface of diaphragm⅔’s of it lies to the left of the midsternal line

Anterior to the vertebral column, posterior to the sternum

HEART ANATOMY

Figure 18.1

COVERINGS OF THE HEARTPericardium – a double-walled sac around the

heart Composed of:

A superficial fibrous pericardiumA deep two-layer serous pericardium

The parietal layer lines the internal surface of the fibrous pericardium

The visceral layer or epicardium lines the surface of the heart

They are separated by the fluid-filled pericardial cavity called the pericardial cavity

Protects and anchors the heartPrevents overfilling of the heart with bloodAllows for the heart to work in a relatively friction-free environment

PERICARDIAL LAYERS OF THE HEART

Figure 18.2

LAYERS OF THE HEART WALL

Epicardium – visceral pericardium

Myocardium – cardiac muscle layer forming the bulk of the heart

Endocardium – endothelial layer of the inner myocardial surface

HEART ANATOMYExternal markings Apex - pointed inferior regionBase - upper regionCoronary sulcusIndentation that separates atria from ventricles

Anterior and posterior interventricular sulcusSeparates right and left ventricles

Internal divisionsAtria (superior) and ventricles (inferior)Interventricular and interatrial septa

ATRIA OF THE HEARTAtria - receiving chambers of the heartReceive venous blood returning to heartSeparated by an interatrial septum (wall)Foramen ovale - opening in interatrial septum in fetus

Fossa ovalis - remnant of foramen ovaleEach atrium has a protruding auriclePectinate muscles mark atrial wallsPump blood into ventricles Blood enters right atria from superior and

inferior venae cavae and coronary sinusBlood enters left atria from pulmonary veins

GROSS ANATOMY OF HEART: FRONTAL SECTION

Figure 18.4e

VENTRICLES OF THE HEARTVentricles are the discharging chambers of the

heartPapillary muscles and trabeculae carneae

muscles mark ventricular wallsSeparated by an interventricular septumContains components of the conduction system

Right ventricle pumps blood into the pulmonary trunk

Left ventricle pumps blood into the aortaThicker myocardium due to greater work load

Pulmonary circulation supplied by right ventricle is a much low pressure system requiring less energy output by ventricle

Systemic circulation supplied by left ventricle is a higher pressure system and thus requires more forceful contractions

EXTERNAL HEART: ANTERIOR VIEW

Figure 18.4b

STRUCTURE OF HEART WALLLeft ventricle –

three times thicker than right

Exerts more pumping force

Flattens right ventricle into a crescent shape

Figure 18.7

HEART VALVES

Heart valves ensure unidirectional blood flow through the heart

Composed of an endocardium with a connective tissue core

Two major typesAtrioventricular valvesSemilunar valvesAtrioventricular (AV) valves lie between the atria

and the ventriclesR-AV valve = tricuspid valveL-AV valve = bicuspid or mitral valveAV valves prevent backflow of blood into the atria

when ventricles contractChordae tendineae anchor AV valves to papillary

muscles of ventricle wallPrevent prolapse of valve back into atrium

SEMILUNAR HEART VALVES

Semilunar valves prevent backflow of blood into the ventricles

Have no chordae tendinae attachments

Aortic semilunar valve lies between the left ventricle and the aorta

Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk

Heart sounds (“lub-dup”) due to valves closing

“Lub” - closing of atrioventricular valves“Dub”- closing of semilunar valves

FIBROUS SKELETONSurrounds all four valvesComposed of dense connective tissue

FunctionsAnchors valve cuspsPrevents overdilation of valve openings

Main point of insertion for cardiac muscle

Blocks direct spread of electrical impulses

HEART VALVES

CONDUCTING SYSTEM

Cardiac muscle tissue has intrinsic ability to:

Generate and conduct impulsesSignal these cells to contract rhythmically

Conducting system A series of specialized cardiac muscle cells

Sinoatrial (SA) node sets the inherent rate of contraction

CONDUCTING SYSTEM

INNERVATIONHeart rate is altered

by external controls

Nerves to the heart include:

Visceral sensory fibersParasympathetic branches of the vagus nerve

Sympathetic fibers – from cervical and upper thoracic chain ganglia

EXTERNAL HEART: POSTERIOR VIEW

Figure 18.4d

MAJOR VESSELS OF THE HEARTVessels returning blood to the heart

include:Superior and inferior venae cavae

Open into the right atriumReturn deoxygenated blood from body cells

Coronary sinusOpens into the right atriumReturns deoxygenated blood from heart muscle (coronary veins)

Right and left pulmonary veinsOpen into the left atriumReturn oxygenated blood from lungs

MAJOR VESSELS OF THE HEART Vessels conveying blood away from the heart

include:Pulmonary trunkCarries deoxygenated blood from right ventricle to lungs

Splits into right and left pulmonary arteriesAscending aortaCarries oxygenated blood away from left ventricle to body organs

Three major branchesBrachiocephalicLeft common carotid, Left subclavian artery

BLOOD FLOW THROUGH THE HEART

Figure 18.6

PATHWAY OF BLOOD THROUGH THE HEART AND LUNGS

Figure 18.5

CORONARY CIRCULATIONThe functional blood supply to the heart muscle itself

R and L Coronary arteries are 1st branches off the ascending aorta

Coronary sinus (vein) empties into R. atriumCollateral routes ensure blood delivery

to heart even if major vessels are occluded

CORONARY CIRCULATION - ARTERIESRight Coronary Artery Supplies blood to

Right atrium and posterior surface of both ventricles

Branches into theMarginal artery - extends across surface of R. ventricle

Posterior interventricular arteryFound in posterior interventricular sulcus

Left Coronary ArterySupplies blood to

Left atrium and left ventricleBranches into

Circumflex arteryAnterior interventricular artery

Found in anterior interventricular sulcusConnected with posterior interventricular artery via arterial anastomoses

CORONARY CIRCULATION: ARTERIAL SUPPLY

Figure 18.7a

CORONARY CIRCULATION - VEINSCoronary sinus - Vein that empties into right atriumReceives deoxygenated blood from:Great cardiac vein - on anterior surfacePosterior cardiac veinDrains area served by circumflex

Middle cardiac veinDrains area served by posterior interventricular artery

Small cardiac veinDrains blood from posterior surfaces of right atrium and ventricle

CORONARY CIRCULATION: VENOUS SUPPLY

Figure 18.7b

MICROSCOPIC ANATOMY OF HEART MUSCLECardiac muscle cellsShort, striated, branched, and interconnectedThe connective tissue endomysium acts as both

tendon and insertionIntercalated discs anchor cardiac cells together

and allow free passage of ionsHeart muscle behaves as a functional syncytiumMany mitochondria (25% of total volume)

MICROSCOPIC ANATOMY OF HEART MUSCLE

Figure 18.11

DISORDERS OF THE HEART

Coronary artery diseaseAtherosclerosis – fatty depositsArteriosclerosis - hardening of the arteries

Angina pectoris – chest painMyocardial infarction – blocked coronary artery

Silent ischemia – no pain or warning Fibrillation - irregular heart beat; may occur in either atria or ventricles