The coronary circulation supplies blood to the heart muscle. It consists of an arterial supply from the right and left coronary arteries, which branch off the aorta. The right coronary artery supplies the right atrium and ventricle as well as parts of the left ventricle and septum. The left coronary artery supplies the left atrium and ventricle as well as parts of the right ventricle and septum. Venous drainage occurs through the coronary sinus and smaller cardiac veins that drain directly into the atria or cavities of the heart. Obstructions of the coronary arteries can cause myocardial infarction and angina pectoris, while coronary angioplasty techniques are used to treat arterial narrowing and blockages.