Our heart gets its own blood supply through the coronary arteries, which encircle the heart like a crown. (Hence the term "coronary," from the Latin word for crown.) There are two main coronary arteries, which branch out of the aorta. These large coronary arteries are about the width of a drinking straw and gradually taper as they descend on the heart. The left main coronary artery divides into two branches called the left anterior descending artery and the circumflex artery. The right coronary artery branches into the posterior descending artery and the marginal artery. These arteries branch into smaller and smaller arteries, some of which penetrate inside the heart. They eventually branch into capillaries, some so fine that it would take ten of them lying side by side to form the thickness of a human hair. Your capillaries deliver oxygen and nutrients and remove waste from your heart's cells. If one or more of the coronary arteries becomes narrowed or completely blocked, blood supply to the heart may be decreased or cut off altogether. The results can be painful and even deadly, including angina (chest pain), tissue death, and myocardial infarction, in other words, a heart attack.
Find out more about what happens when coronary arteries become blocked: