Prof. J.P.N. Mishra
The heart is situated in the thoracic cavity between the lungs. This area is termed as mediastinum. The base of the cone-shaped heart is uppermost, behind the sternum, and the great vessels enter or leave here. The apex (tip) of the heart points downward and is just above the diaphragm to the left of the midline. This is why we may think of the heart as being on the left side, because the strongest beat can be heard or felt here. The heart is enclosed in the pericardial membranes, of which there are three layers (Fig. 1-1). The outermost is the fibrous pericardium, a loose-fitting sac of strong fibrous connective tissue that extends inferiorly over the diaphragm and superiorly over the bases of the large vessels that enter and leave the heart. The serous pericardium is a folded membrane; the fold gives it two layers, parietal and visceral. Lining the fibrous pericardium is the parietal pericardium. On the surface of the heart muscle is the visceral pericardium, often called the epicardium. Between the parietal and visceral pericardial membranes is serous fluid, which prevents friction as the heart beats (Saladin, 2004).
Fig. 1-1. Layers of the wall of the heart and the pericardial membranes
