Heart

Structure

The heart has four chambers: two atria on top and two ventricles below. The right side handles deoxygenated blood; the left side handles oxygenated blood. Four valves (tricuspid, pulmonary, mitral, aortic) prevent backflow as the chambers contract in sequence.

Function

At rest, the heart beats roughly 60 to 100 times per minute, pumping about 5 liters of blood per minute. The sinoatrial node sets the rhythm, while the atrioventricular node coordinates the delay between atrial and ventricular contraction.

Position

It sits in the mediastinum, tilted slightly to the left, with its apex pointing toward the lower-left rib. The pericardium, a double-layered sac, anchors and protects it.