The heart is located in the center of the chest. It sits directly above the diaphragm and just beneath the sternum in a space between the lungs called the mediastinum. Its position is usually more horizontal than vertical, but may vary considerably from one person to the next. The apex (tip) of the heart is pointed forward, downward, and toward the left, and the inferior (diaphragmatic) surface lies directly on the diaphragm
The heart is freely movable and unattached to any of the organs that surround it. It is maintained in its proper position by continuity with the major vessels that carry blood from and to it, and by an enclosing fibrous sac called the pericardium. This tough membrane separates the heart from other structures in the mediastinum, and normally is in direct contact with the cardiac surface. A small amount of lubricating pericardial fluid reduces friction between the pericardium and the beating heart.