(See also HEART.) The right coronary artery arises from the right aortic sinus and passes into the right atrio-ventricular groove to supply the right ventricle, part of the intraventricular septum and the inferior part of the left ventricle. The left coronary artery arises from the left sinus and divides into an anterior descending branch which supplies the septum and the anterior and apical parts of the heart, and the circumflex branch which passes into the left atrio-ventricular groove and supplies the lateral posterior surfaces of the heart. Small anastomoses exist between the coronary arteries and they have the potential of enlarging if the blood-flow through a neighbouring coronary artery is compromised. (See CIRCULATORY SYSTEM OF THE BLOOD for diagram of heart and coronary arteries.) Coronary artery disease is damage to the heart caused by the narrowing or blockage of these arteries. It commonly presents as ANGINA PECTORIS or acute myocardial infarction (see HEART, DISEASES OF.)