The heart muscle, the most important muscle in your body, is fuelled by the coronary arteries, which originate in the aorta where it leaves the heart. There are two main arteries, one on the right and one on the left. The right coronary artery supplies the right side of the heart, and the lower part of the left ventricle, which is the high-pressure chamber that pumps the blood through our bodies. The artery on the left divides into two branches (the left anterior descending and the circumflex arteries), which together supply the rest of the left ventricle. These three arteries run down over the surface of the heart, and send branches into the muscle. It's the narrowing or blockage of these arteries by atheromatous plaque which causes coronary artery disease (also known as coronary heart disease).