Heart Anatomy

Heart Anatomy

• Approximately the size of a fist• Location

– In the mediastinum between second rib and fifth intercostal space

– On the superior surface of diaphragm– Two-thirds to the left of the midsternal line

• Enclosed in pericardium, a double-walled sac

PLAY Animation: Rotatable heart

Figure 18.1a

Point ofmaximalintensity(PMI)

Diaphragm

(a)

Sternum2nd ribMidsternal line

Figure 18.1c

(c)

Superiorvena cava

Left lung

AortaParietalpleura (cut)

Pericardium(cut)

Pulmonarytrunk

DiaphragmApex ofheart

Pericardium

• Superficial fibrous pericardium• Protects, anchors, and prevents overfilling

Pericardium

• Deep two-layered serous pericardium– Separated by fluid-filled pericardial cavity

(decreases friction)

Figure 18.2

Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardium

Pulmonarytrunk

Heart chamber

Heartwall

PericardiumMyocardium

Layers of the Heart Wall1. Epicardium—visceral layer of the serous

pericardium

Layers of the Heart Wall

2. Myocardium – Spiral bundles of cardiac muscle cells – Fibrous skeleton of the heart: crisscrossing,

interlacing layer of connective tissue• Anchors cardiac muscle fibers • Supports great vessels and valves• Limits spread of action potentials to specific paths

Layers of the Heart Wall

3. Endocardium is continuous with endothelial lining of blood vessels

Figure 18.2

Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardium

Pulmonarytrunk

Heart chamber

Heartwall

PericardiumMyocardium

Figure 18.3

Cardiacmusclebundles

Chambers

• Four chambers– Two atria

• Separated internally by the interatrial septum• Coronary sulcus (atrioventricular groove) encircles the

junction of the atria and ventricles• Auricles increase atrial volume

Chambers

• Two ventricles– Separated by the interventricular septum– Anterior and posterior interventricular sulci mark

the position of the septum externally

Figure 18.4b

(b) Anterior view

Brachiocephalic trunk

Superior vena cava

Right pulmonaryarteryAscending aortaPulmonary trunk

Right pulmonaryveins

Right atriumRight coronary artery(in coronary sulcus)Anterior cardiac veinRight ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava

Left common carotidarteryLeft subclavian artery

Ligamentum arteriosumLeft pulmonary artery

Left pulmonary veins

Circumflex artery

Left coronary artery(in coronary sulcus)

Left ventricle

Great cardiac veinAnterior interventricularartery (in anteriorinterventricular sulcus)Apex

Aortic arch

Auricle ofleft atrium

Atria: The Receiving Chamberson diagram

• Vessels entering right atrium– Superior vena cava – Inferior vena cava– Coronary sinus

• Vessels entering left atrium– Right and left pulmonary veins

Ventricles: The Discharging Chambers on diagram

• Walls are ridged by trabeculae carneae• Papillary muscles project into the ventricular

cavities• Vessel leaving the right ventricle

– Pulmonary trunk• Vessel leaving the left ventricle

– Aorta

Figure 18.4e

AortaLeft pulmonaryarteryLeft atriumLeft pulmonaryveins

Mitral (bicuspid)valve

Aortic valvePulmonary valveLeft ventricle

Papillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium

(e) Frontal section

Superior vena cavaRight pulmonaryarteryPulmonary trunkRight atriumRight pulmonaryveinsFossa ovalisPectinate musclesTricuspid valveRight ventricle

Chordae tendineaeTrabeculae carneaeInferior vena cava

Pathway of Blood Through the Heart

• The heart is two side-by-side pumps– Right side is the pump for the pulmonary circuit

• Vessels that carry blood to and from the lungs– Left side is the pump for the systemic circuit

• Vessels that carry the blood to and from all body tissues

Figure 18.5

Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood

Capillary bedsof lungs wheregas exchangeoccurs

Capillary beds of allbody tissues wheregas exchange occurs

Pulmonary veinsPulmonary arteries

PulmonaryCircuit

SystemicCircuit

Aorta and branches

Left atrium

HeartLeft ventricleRight atrium

Right ventricle

Venae cavae

Pathway of Blood Through the Heart

• Right atrium tricuspid valve right ventricle• Right ventricle pulmonary semilunar valve

pulmonary trunk pulmonary arteries lungs

PLAY Animation: Rotatable heart (sectioned)

PLAY Animation: Rotatable heart (sectioned)

Pathway of Blood Through the Heart

• Lungs pulmonary veins left atrium• Left atrium bicuspid valve left ventricle• Left ventricle aortic semilunar valve aorta• Aorta systemic circulation

Pathway of Blood Through the Heart

• Equal volumes of blood are pumped to the pulmonary and systemic circuits

• Pulmonary circuit is a short, low-pressure circulation

• Systemic circuit blood encounters much resistance in the long pathways

• Anatomy of the ventricles reflects these differences

Figure 18.6

Rightventricle

Leftventricle

Interventricularseptum

Coronary Circulation

• The functional blood supply to the heart muscle itself

• Arterial supply varies considerably and contains many anastomoses (junctions) among branches

• Collateral routes provide additional routes for blood delivery

Coronary Circulation don’t copy

• Arteries – Right and left coronary (in atrioventricular

groove), marginal, circumflex, and anterior interventricular arteries

• Veins – Small cardiac, anterior cardiac, and great cardiac

veins

Figure 18.4d

(d) Posterior surface view

AortaLeft pulmonaryarteryLeft pulmonaryveinsAuricle of leftatriumLeft atriumGreat cardiacveinPosterior veinof left ventricleLeft ventricle

Apex

Superior vena cavaRight pulmonary arteryRight pulmonary veins

Right atrium

Inferior vena cava

Right coronary artery(in coronary sulcus)

Coronary sinus

Posteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricle

Homeostatic Imbalances

• Angina pectoris– Thoracic pain caused by a fleeting deficiency in

blood delivery to the myocardium– Cells are weakened

• Myocardial infarction (heart attack)– Prolonged coronary blockage– Areas of cell death are repaired with

noncontractile scar tissue

Heart Valves

• Ensure unidirectional blood flow through the heart• Atrioventricular (AV) valves

– Prevent backflow into the atria when ventricles contract– Tricuspid valve (right)– Mitral valve (left)

• Chordae tendineae anchor AV valve cusps to papillary muscles

Heart Valves

• Semilunar (SL) valves– Prevent backflow into the ventricles when

ventricles relax– Aortic semilunar valve– Pulmonary semilunar valve

Figure 18.8a

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Pulmonary valveAortic valveArea of cutawayMitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valve

(a)

Mitral(left atrioventricular)valveAortic valvePulmonaryvalveFibrous

skeletonAnterior

Figure 18.8b

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Figure 18.8c

Pulmonaryvalve

AorticvalveArea ofcutawayMitralvalve

Tricuspidvalve

Chordae tendineaeattached to tricuspid valve flap

Papillarymuscle

(c)

Figure 18.8d

PulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalve

Mitral valveChordaetendineae

Interventricularseptum

Myocardiumof left ventricle

Opening of inferiorvena cavaTricuspid valve

Papillarymuscles

Myocardiumof rightventricle

(d)

Figure 18.9

1 Blood returning to theheart fills atria, puttingpressure againstatrioventricular valves;atrioventricular valves areforced open.

1 Ventricles contract, forcingblood against atrioventricularvalve cusps.

2 As ventricles fill,atrioventricular valve flapshang limply into ventricles.

2 Atrioventricular valvesclose.

3 Atria contract, forcingadditional blood into ventricles.

3 Papillary musclescontract and chordaetendineae tighten,preventing valve flapsfrom everting into atria.

(a) AV valves open; atrial pressure greater than ventricular pressure

(b) AV valves closed; atrial pressure less than ventricular pressure

Direction ofblood flowAtrium

Ventricle

Cusp ofatrioventricularvalve (open)

Chordaetendineae

Papillarymuscle

Atrium

Blood inventricle

Cusps ofatrioventricularvalve (closed)

Figure 18.10

As ventriclescontract andintraventricularpressure rises,blood is pushed upagainst semilunarvalves, forcing themopen.

As ventricles relaxand intraventricularpressure falls, bloodflows back fromarteries, filling thecusps of semilunarvalves and forcingthem to close.

(a) Semilunar valves open

(b) Semilunar valves closed

AortaPulmonarytrunk

Heart Sounds

• Two sounds (lub-dup) associated with closing of heart valves– First sound occurs as AV valves close and signifies

beginning of systole– Second sound occurs when SL valves close at the

beginning of ventricular diastole • Heart murmurs: abnormal heart sounds most

often indicative of valve problems usually the valve not closing all the way.

Figure 18.19

Tricuspid valve sounds typically heard in right sternal margin of 5th intercostal space

Aortic valve sounds heard in 2nd intercostal space atright sternal margin

Pulmonary valvesounds heard in 2ndintercostal space at leftsternal margin

Mitral valve soundsheard over heart apex(in 5th intercostal space)in line with middle ofclavicle

Mechanical Events: The Cardiac Cycle

• Cardiac cycle: all events associated with blood flow through the heart during one complete heartbeat– Systole—contraction – Diastole—relaxation

Other Factors that Influence Heart Rate

• Age• Gender• Exercise• Body temperature

Developmental Aspects of the Heart don’t copy

• Embryonic heart chambers– Sinus venous– Atrium– Ventricle– Bulbus cordis

Figure 18.23

(a) Day 20: Endothelial tubes begin to fuse.

(b) Day 22: Heart starts pumping.

(c) Day 24: Heart continues to elongate and starts to bend.

(d) Day 28: Bending continues as ventricle moves caudally and atrium moves cranially.

(e) Day 35: Bending is complete.

Tubularheart Ventricle

VentricleAtrium

Venous end Venous end

Arterial end Arterial end4a4

321

AortaSuperiorvenacava

Inferiorvena cava

Ductusarteriosus

Pulmonarytrunk

Foramenovale

Ventricle

Developmental Aspects of the Heart

• Fetal heart structures that bypass pulmonary circulation– Foramen ovale connects the two atria – Ductus arteriosus connects the pulmonary trunk

and the aorta

Developmental Aspects of the Heart

• Congenital heart defects– Lead to mixing of systemic and pulmonary blood– Involve narrowed valves or vessels that increase

the workload on the heart

Figure 18.24

Occurs inabout 1 in every500 births

Occurs inabout 1 in every 1500 births

Narrowedaorta

Occurs inabout 1 in every 2000births

Ventricular septal defect.The superior part of the inter-ventricular septum fails to form; thus, blood mixes between the two ventricles. More blood is shunted from left to right because the left ventricle is stronger.

(a) Coarctation of the aorta. A part of the aorta is narrowed,increasing the workload of the left ventricle.

(b) Tetralogy of Fallot. Multiple defects (tetra = four): (1) Pulmonary trunk too narrow and pulmonary valve stenosed, resulting in (2) hypertrophied right ventricle; (3) ventricular septal defect; (4) aorta opens from both ventricles.

(c)

Age-Related Changes Affecting the Heart

• Sclerosis and thickening of valve flaps• Decline in cardiac reserve• Fibrosis of cardiac muscle• Atherosclerosis