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The Heart

size of a fist

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
Anterior to the vertebral column, posterior to the sternum
Enclosed in pericardium, a double-walled sac


Protects, anchors, and prevents overfilling


Deep two-layered serous pericardium
Parietal layer lines the internal surface of the fibrous pericardium
Visceral layer (epicardium) on external surface of the heart
Separated by fluid-filled pericardial cavity (decreases friction)


visceral layer of the serous pericardium


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


continuous with endothelial lining of blood vessels


Separated internally by the interatrial septum

Coronary sulcus (atrioventricular groove) encircles the junction of the atria and ventricles

Auricles increase atrial volume


Separated by the interventricular septum

Anterior and posterior interventricular sulci mark the position of the septum externally

Atria: The Receiving Chambers

Walls are ridged by pectinate muscles

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

Walls are ridged by trabeculae carneae

Papillary muscles project into the ventricular cavities

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: Arteries

Right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular arteries

Coronary Circulation: Veins

Small cardiac, middle, and great cardiac veins

Coronary sinus

Homeostatic Imbalances

Angina pectoris

Myocardial infarction (heart attack)

Angina pectoris

Thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium

Myocardial infarction

(heart attack)

Prolonged coronary blockage

Areas of cell death are repaired with noncontractile scar tissue

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