The coronary arteries are the two blood vessels which supply the heart with oxygenated blood. There is a left and a right coronary artery and they are the first branches of the aorta. Each of them arises from the corresponding left and right aortic sinus, which is one of the dilated parts at the base of the ascending aorta above each one of the cusp of the aortic valve.
The left coronary artery originates from the left aortic sinus and descends obliquely, giving off its two main branches; the anterior interventricular artery, which travels all the way down to reach the apex of heart, and the circumflex artery, which curves to the left in the atrioventricular groove, winding around the border of heart to the posterior side of this organ.
The right coronary artery arises from the right aortic sinus and runs around to the right side of heart along the atrioventricular groove, giving off branches that supply both the right atrium and ventricle. On the posterior side of heart, it gives off the posterior interventricular branch. You have to bear in mind that the right coronary has less side branches and blood volume than the left coronary artery.
Anterior aspect of human heart, showing the two coronary arteries.
