Located almost in the center of the chest, the adult human heart is about the size of two fists held side-by-side.

The heart is a pump made of muscle tissue. Its pumping action is regulated by electrical impulses.

Coronary arteries supply blood to the heart muscle. There are two main coronary arteries: the right and the left.

Heart disease is one of the most serious health problems in the United States. Find out more facts and figures on this topic.

Detailed anatomical description of the heart valves, including simple definitions and a labeled, full-color illustration

Heart valves prevent the backward flow of blood. They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle.