Heart AnatomyHeart Anatomy

Approximately the Approximately the size of your fistsize of your fist

LocationLocation• Superior surface of Superior surface of

diaphragmdiaphragm• Left of the midlineLeft of the midline• Anterior to the Anterior to the

vertebral column, vertebral column, posterior to the posterior to the sternumsternum

Heart AnatomyHeart Anatomy

Figure 18.1

Coverings of the Heart: Coverings of the Heart: AnatomyAnatomy

Pericardium – a double-walled sac Pericardium – a double-walled sac around the heart composed of:around the heart composed of:• A superficial fibrous pericardiumA superficial fibrous pericardium• A deep two-layer serous pericardiumA deep two-layer serous pericardium

The parietal layer lines the internal surface The parietal layer lines the internal surface of the fibrous pericardiumof the fibrous pericardium

The visceral layer or epicardium lines the The visceral layer or epicardium lines the surface of the heartsurface of the heart

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

Coverings of the Heart: Coverings of the Heart: PhysiologyPhysiology

The pericardium:The pericardium:• Protects and anchors the heartProtects and anchors the heart• Prevents overfilling of the heart with Prevents overfilling of the heart with

bloodblood• Allows for the heart to work in a Allows for the heart to work in a

relatively friction-free environmentrelatively friction-free environment

Pericardial Layers of the HeartPericardial Layers of the Heart

Figure 18.2

Heart WallHeart Wall

Epicardium – visceral layer of the Epicardium – visceral layer of the serous pericardiumserous pericardium

Myocardium – cardiac muscle layer Myocardium – cardiac muscle layer forming the bulk of the heartforming the bulk of the heart

Fibrous skeleton of the heart – Fibrous skeleton of the heart – crisscrossing, interlacing layer of crisscrossing, interlacing layer of connective tissueconnective tissue

Endocardium – endothelial layer of the Endocardium – endothelial layer of the inner myocardial surfaceinner myocardial surface

Cardiac Muscle BundlesCardiac Muscle Bundles

Figure 18.3

External Heart: Major Vessels of External Heart: Major Vessels of the Heart (Anterior View)the Heart (Anterior View)

Vessels returning blood to the heart include:Vessels returning blood to the heart include:• Superior and inferior venae cavaSuperior and inferior venae cava• Right and left pulmonary veinsRight and left pulmonary veins

Vessels conveying blood away from the heart:Vessels conveying blood away from the heart:• Pulmonary trunk, which splits into right and Pulmonary trunk, which splits into right and

left pulmonary arteriesleft pulmonary arteries• Ascending aorta (three branches) Ascending aorta (three branches)

Figure 18.4d

(d)

Superiorvena cavaRightpulmonary artery

Rightpulmonary veins

Right atrium

Right coronaryartery (in coronarysulcus)

Right ventricle

Coronary sinus

Middle cardiac vein

Left pulmonary artery

Left atrium

Auricleof left atrium

Left ventricle

Posterior veinof left ventricle

Posteriorinterventricular artery(in posteriorinterventricular sulcus)

Great cardiac vein

Apex

Leftpulmonary veins

Inferiorvena cava

Aorta

Figure 18.4e

(e)

Superior vena cava

Rightpulmonary arteryPulmonary trunk

Right atriumRightpulmonary veinsFossaovalisPectinatemuscles

TricuspidvalveRight ventricle

ChordaetendineaeTrabeculaecarneaeInferiorvena cava

Aorta

Leftpulmonary arteryLeft atriumLeftpulmonary veins

Pulmonaryvalve

Aorticvalve

Mitral (bicuspid) valve

Left ventricle

PapillarymuscleInterventricularseptumMyocardium

VisceralpericardiumEndocardium

Atria of the HeartAtria of the Heart

Atria are the receiving chambers of Atria are the receiving chambers of the heartthe heart

Each atrium has a protruding auricleEach atrium has a protruding auricle Pectinate muscles mark atrial wallsPectinate muscles mark atrial walls Blood enters right atria from superior Blood enters right atria from superior

and inferior venae cavae and coronary and inferior venae cavae and coronary sinussinus

Blood enters left atria from pulmonary Blood enters left atria from pulmonary veinsveins

Ventricles of the HeartVentricles of the Heart

Ventricles are the discharging Ventricles are the discharging chambers of the heartchambers of the heart

Papillary muscles and trabeculae Papillary muscles and trabeculae carneae muscles mark ventricular carneae muscles mark ventricular wallswalls

Right ventricle pumps blood into the Right ventricle pumps blood into the pulmonary trunkpulmonary trunk

Left ventricle pumps blood into the Left ventricle pumps blood into the aortaaorta

Right and Left VentriclesRight and Left Ventricles

Figure 18.6

Pathway of Blood Through the Pathway of Blood Through the Heart and LungsHeart and Lungs

Right atrium Right atrium tricuspid valve tricuspid valve right right ventricleventricle

Right ventricle Right ventricle pulmonary semilunar pulmonary semilunar valve valve pulmonary arteries pulmonary arteries lungs lungs

Lungs Lungs pulmonary veins pulmonary veins left atrium left atrium Left atrium Left atrium bicuspid valve bicuspid valve left ventricle left ventricle Left ventricle Left ventricle aortic semilunar valve aortic semilunar valve

aortaaorta Aorta Aorta systemic circulation systemic circulation

Figure 18.5

http://www.pbs.org/wnet/redgold/journey/phase2_a1.html

Coronary CirculationCoronary Circulation

Coronary circulation is the functional Coronary circulation is the functional blood supply to the heart muscle blood supply to the heart muscle itselfitself

Collateral routes ensure blood Collateral routes ensure blood delivery to heart even if major delivery to heart even if major vessels are occludedvessels are occluded

Coronary Circulation: Arterial Coronary Circulation: Arterial SupplySupply

Figure 18.7a

Coronary Circulation: Venous Coronary Circulation: Venous SupplySupply

Figure 18.7b

Heart ValvesHeart Valves

Heart valves ensure unidirectional Heart valves ensure unidirectional blood flow through the heartblood flow through the heart

Atrioventricular (AV) valvesAtrioventricular (AV) valves lie lie between the atria and the ventriclesbetween the atria and the ventricles

AV valves prevent backflow into the AV valves prevent backflow into the atria when ventricles contractatria when ventricles contract

Chordae tendineae anchor AV valves Chordae tendineae anchor AV valves to papillary musclesto papillary muscles

Heart ValvesHeart Valves

Aortic semilunar valveAortic semilunar valve lies between lies between the left ventricle and the aorta the left ventricle and the aorta

Pulmonary semilunar valvePulmonary semilunar valve lies lies between the right ventricle and between the right ventricle and pulmonary trunkpulmonary trunk

Semilunar valvesSemilunar valves prevent backflow of prevent backflow of blood into the ventriclesblood into the ventricles

Heart ValvesHeart Valves

Figure 18.8a, b

Heart ValvesHeart Valves

Figure 18.8c, d

Atrioventricular Valve FunctionAtrioventricular Valve Function

Figure 18.9

Semilunar Valve FunctionSemilunar Valve Function

Figure 18.10

Microscopic Anatomy of Heart Microscopic Anatomy of Heart MuscleMuscle

Cardiac muscle is striated, short, fat, Cardiac muscle is striated, short, fat, branched, and interconnectedbranched, and interconnected

The connective tissue endomysium acts as The connective tissue endomysium acts as both tendon and insertionboth tendon and insertion

Intercalated discs anchor cardiac cells Intercalated discs anchor cardiac cells together and allow free passage of ionstogether and allow free passage of ions

Heart muscle behaves as a functional Heart muscle behaves as a functional syncytiumsyncytium

Microscopic Anatomy of Cardiac Microscopic Anatomy of Cardiac MuscleMuscle

Figure 18.11

Cardiac Muscle ContractionCardiac Muscle Contraction

Heart muscle:Heart muscle:• Is stimulated by nerves and is self-Is stimulated by nerves and is self-

excitable (automaticity)excitable (automaticity)• Contracts as a unitContracts as a unit

Cardiac muscle contraction is similar Cardiac muscle contraction is similar to skeletal muscle contractionto skeletal muscle contraction

Heart Physiology: Intrinsic Heart Physiology: Intrinsic Conduction SystemConduction System

Autorhythmic cells:Autorhythmic cells:• Initiate action potentials Initiate action potentials • Have unstable resting potentials called Have unstable resting potentials called

pacemaker potentialspacemaker potentials• Use calcium influx (rather than sodium) Use calcium influx (rather than sodium)

for rising phase of the action potentialfor rising phase of the action potential

http://www.phschool.com/science/biology_place/biocoach/cardio1/intconduct.html

Pacemaker and Action Pacemaker and Action Potentials of the HeartPotentials of the Heart

Figure 18.13

Heart Physiology: Sequence of Heart Physiology: Sequence of ExcitationExcitation

Sinoatrial (SA) node generates Sinoatrial (SA) node generates impulses about 75 times/minuteimpulses about 75 times/minute

Atrioventricular (AV) node delays the Atrioventricular (AV) node delays the impulse approximately 0.1 secondimpulse approximately 0.1 second

Impulse passes from atria to Impulse passes from atria to ventricles via the atrioventricular ventricles via the atrioventricular bundle (bundle of His)bundle (bundle of His)

Heart Physiology: Sequence of Heart Physiology: Sequence of ExcitationExcitation

AV bundle splits into two pathways in AV bundle splits into two pathways in the interventricular septum (bundle the interventricular septum (bundle branches)branches)• Bundle branches carry the impulse Bundle branches carry the impulse

toward the apex of the hearttoward the apex of the heart• Purkinje fibers carry the impulse to the Purkinje fibers carry the impulse to the

heart apex and ventricular wallsheart apex and ventricular walls

Cardiac Intrinsic ConductionCardiac Intrinsic Conduction

Figure 18.14a

SA node generates impulse;atrial excitation begins

Impulse delayedat AV node

Impulse passes toheart apex; ventricular

excitation begins

Ventricular excitationcomplete

SA node AV node Purkinjefibers

Bundlebranches

Figure 18.17

Heart Excitation Related to ECGHeart Excitation Related to ECG

http://www.phschool.com/science/biology_place/biocoach/cardio1/intconduct.html

SA node generates impulse;atrial excitation begins

SA node

Figure 18.17

Heart Excitation Related to ECGHeart Excitation Related to ECG

Impulse delayedat AV node

AV node

Figure 18.17

Heart Excitation Related to ECGHeart Excitation Related to ECG

Impulse passes toheart apex; ventricularexcitation begins

Bundlebranches

Figure 18.17

Heart Excitation Related to ECGHeart Excitation Related to ECG

Ventricular excitationcomplete

Purkinjefibers

Figure 18.17

Heart Excitation Related to ECGHeart Excitation Related to ECG

SA node generates impulse;atrial excitation begins

Impulse delayedat AV node

Impulse passes toheart apex; ventricular

excitation begins

Ventricular excitationcomplete

SA node AV node Purkinjefibers

Bundlebranches

Figure 18.17

Heart Excitation Related to ECGHeart Excitation Related to ECG

Extrinsic Innervation of the Extrinsic Innervation of the HeartHeart

Heart is stimulated Heart is stimulated by the sympathetic by the sympathetic cardioacceleratory cardioacceleratory center center

Heart is inhibited by Heart is inhibited by the parasympathetic the parasympathetic cardioinhibitory cardioinhibitory centercenter

Figure 18.15

ElectrocardiographyElectrocardiography Electrical activity is recorded by Electrical activity is recorded by

electrocardiogram (ECG)electrocardiogram (ECG) P wave corresponds to depolarization of SA P wave corresponds to depolarization of SA

nodenode QRS complex corresponds to ventricular QRS complex corresponds to ventricular

depolarization (contracting)depolarization (contracting) T wave corresponds to ventricular T wave corresponds to ventricular

repolarization (go back to normal state)repolarization (go back to normal state)

PLAYPLAY InterActive Physiology ®: Intrinsic Conduction System, pages 3–6

Heart SoundsHeart Sounds

Figure 18.19

ElectrocardiographyElectrocardiography

Figure 18.16

Heart SoundsHeart Sounds

Heart sounds (lub-dup) are Heart sounds (lub-dup) are associated with closing of heart associated with closing of heart valvesvalves• First sound occurs as AV valves close First sound occurs as AV valves close

and signifies beginning of systoleand signifies beginning of systole• Second sound occurs when SL valves Second sound occurs when SL valves

close at the beginning of ventricular close at the beginning of ventricular diastolediastole

Atrial fibrillation

Ventricular fibrillation

Ventricular tachycardia

Cardiac CycleCardiac Cycle

Cardiac cycle refers to all events Cardiac cycle refers to all events associated with blood flow through associated with blood flow through the heartthe heart• Systole – contraction of heart muscleSystole – contraction of heart muscle• Diastole – relaxation of heart muscleDiastole – relaxation of heart muscle

Phases of the Cardiac CyclePhases of the Cardiac Cycle

Ventricular filling – mid-to-late Ventricular filling – mid-to-late diastolediastole• Heart blood pressure is low as blood Heart blood pressure is low as blood

enters atria and flows into ventriclesenters atria and flows into ventricles• AV valves are open, then atrial systole AV valves are open, then atrial systole

occursoccurs

Phases of the Cardiac CyclePhases of the Cardiac Cycle

Ventricular systoleVentricular systole• Atria relax Atria relax • Rising ventricular pressure results in Rising ventricular pressure results in

closing of AV valvesclosing of AV valves• Ventricular ejection phase opens Ventricular ejection phase opens

semilunar valvessemilunar valves

Phases of the Cardiac CyclePhases of the Cardiac Cycle

Isovolumetric relaxation – early Isovolumetric relaxation – early diastolediastole• Ventricles relaxVentricles relax

PLAYPLAY InterActive Physiology ®: Cardiac Cycle, pages 3–18

Figure 18.20

Examples of Congenital Heart Examples of Congenital Heart DefectsDefects

Figure 18.25

Age-Related Changes Affecting Age-Related Changes Affecting the Heartthe Heart

Sclerosis and thickening of valve Sclerosis and thickening of valve flapsflaps

Decline in cardiac reserveDecline in cardiac reserve Fibrosis of cardiac muscleFibrosis of cardiac muscle AtherosclerosisAtherosclerosis