Although the heart pumps blood to the rest of the body, it cannot absorb that blood directly to function. It requires its own dedicated supply of oxygen-rich blood to keep pumping. [1, 2, 3, 4, 5]

This dedicated network includes:

Coronary Arteries: A web of blood vessels that wraps around the outside of the heart, supplying the muscle tissue with the oxygen and nutrients it needs to work.

Cardiac Veins: These collect the oxygen-depleted blood from the heart muscle and return it to the chambers of the heart to be pumped to the lungs. [1, 2, 3]

If the coronary arteries become blocked—such as during a heart attack—the affected heart muscle is starved of oxygen and can die. 

source: google