The Heart - 11 March 2008

Mediastinum

Superior

Superior thoracic outlet

Sternal angle & T4

Thymus, great vessels, vagus & phrenic nerves; esophagus, trachea, thoracic duct; lymph

nodes & vessels

Inferior

Anterior

Space between pericardium and sternum;

Thymus, lymph nodes & vessels

Middle

Heart in pericardial sac, ascending aorta,

lower half of superior vena cava, pulmonary

trunk & veins; phrenic nerve

Posterior

Esophagus, trachea & the two bronchi, thoracic

descending aorta, azygos & hemiazygos veins,

thoracic duct, sympathetic trunks & splanchnic

nerves; lymph nodes.

Rosse & Gaddum-Rosse, 1997; Fig. 22-1

Sinuses of pericardium

Transverse sinus

Passes posterior to the outflow of the heart

Oblique sinus

Blind pouch bounded by the inferior venacava and the pulmonary arteries

Rosse & Gaddum-Rosse, 1997; Fig. 21-3. See Netter 2006, pl. 215

Pericardium & Pleura

Visceral pleura over lungs

Parietal pleura, fibrous pericardium and parietal serous pericardium fused into a single unit

Phrenic nerve and pericardiacophrenic a & v between pleura and fibrous pericardium

Visceral pericardium (epicardium) over surface of heart

Rosse & Gaddum-Rosse, 1997; Fig. 19-17. See Moore & Dalley 2006, Fig 1-35

Surfaces of heart

Sternocostal surface

Diaphragmatic surface

Base

Right margin

Left margin

Know structures associated with each surface

Netter 2003, pl. 208; 2006, pl. 212

Coronary Arteries

• Right Coronary Artery

– SA Nodal branch

– Right marginal branch

– Posterior interventricular branch

• Left Coronary Artery

– Anterior interventricular branch

– Circumflex branch

– Posterior left ventricular branch

Cardiac veins

• Great cardiac vein

– Runs in coronary sinus

• Middle cardiac vein

– Parallel to posterior interventricular a.

• Coronary sinus

– The confluence of the Middle & Great Cardiac vv.

– Empties into the right atrium

Netter 2003, pl. 212; Netter 2006, pl. 216

Internal structures of the heart

• Right atrium

– Pectinate muscles

– Crista terminalis

– Fossa ovalis

– Ostium of coronary sinus

– Tricuspid valve

• Right ventricle

– Papillary muscles

– Chordae tendinae

– Septomarginal trabecula

– Pulmonary valve

Internal structures of the heart

• Left ventricle

– Mitral valve

– Trabeculae carnae

– Papillary muscles

– Aortic valve

• Left atrium

– Pulmonary veins

– Mitral valve

Netter 2003, pl. 216, 217; 2006, pl. 220, 221

Interventricular septum

Muscular interventricular septum

membranous interventricular septum

membranousatrioventricular septum

Netter 2003, pl. 220; 2006, pl. 224

Fibrous rings of heart

Provide attachment for valves and myocardium

Insulate atria and ventricles from propagating myopotentials

Netter 2003, pl. 218; 2006, pl. 222

Conducting System of Heart

• Modified cardiomyocytes

• Sinuatrial node

– Controls the rate of contraction

• Atrioventricular node

– Receives impulses from SA node

– Passes to AV bundle

• Atrioventricular bundle

– Traverses the fibrous framework of the heart into the ventricles

• Bundle branches

– Distribute impulses to papillary muscles of both ventricles

The sinuatrial node is supplied with both parasympathetic and sympathetic innervation via the cardiac plexus.

Netter 2003, pl. 221; 2006, pl. 225

Stimulation affects the rate of nodal discharge.

Sympathetic stimulation accelerates heart rate.

Parasympathetic stimulation slows heart rate.

Cardiac Cycle - diastole

diastole - atria fill

late diastole - ventricles fill

Netter, 1997; plate 210; 2003, pl. 218; 2006, pl. 222
Moore & Dalley, 2006; Fig. 1.45

Cardiac Cycle - systole

early systole - ventricular contraction begins

late systole - ventricles empty

Netter, 1997; plate 210; 2003, pl. 218
Moore & Dalley, 2006; Fig. 1.45