CH 18: Gross Anatomy of the Heart J.F. Thompson, Ph.D.

Located in the Ventral Body Cavity Ventral body cavity thoracic pleural pericardial mediastinum abdominopelvic abdominal pelvic

The Size of the Heart About same size as a closed fist the base is the wider superior portion the apex is the point

Pericardium The sac containing the heart

Fibrous Pericardium rests on and is attached to diaphragm a tough, inelastic sac of fibrous connective tissue anchored to the blood vessels entering and leaving the base of the heart protects and anchors the heart; prevents overfilling of the chambers of the heart

Parietal (Outer) Serous Pericardium simple squamous epithelium forms outer parietal layer bound to fibrous pericardium secretes a serous (watery) lubricating fluid reduces friction as the heart contracts and twists

Visceral (Inner) Serous Pericardium simple squamous epithelium forms the epicardium forms visceral layer bound to the myocardium of the heart secretes serous fluid reduces friction as the heart pumps, contracts and twists

Heart wall - Three layers Epicardium (outer) visceral layer of pericardium thin, transparent smooth, slippery Myocardium (middle) mass of cardiac muscle Endocardium (inner) endothelium over thin connective tissue smooth lining for the chambers and valves continuous with blood vessel endothelium

Myocardium (Cardiac Muscle) Cardiac muscle cells are involuntary, striated, branched Each fiber is connected to the others by intercalated discs gap junctions allow action potentials to pass from fiber to fiber desmosomes (“spot welds”) to prevent cardiac fibers from separating during contractions

Intercalated Discs [Note the striations and recall the sliding filament method of muscle contraction.]

Surface of the Heart External landmarks Atrioventricular grooves separate atria from ventricles Anterior/posterior interventricular sulcus separates right and left ventricles Coronary vessels run in these grooves

End Anatomy of the Heart CH 18