<Li> If the posterior descending artery is supplied by the circumflex artery (CX), a branch of the left artery, then the coronary circulation can be classified as "left - dominant". </Li> <Li> If the posterior descending artery is supplied by both the right coronary artery and the circumflex artery, then the coronary circulation can be classified as "co-dominant". </Li> <P> Approximately 70% of the general population are right - dominant, 20% are co-dominant, and 10% are left - dominant . A precise anatomic definition of dominance would be the artery which gives off supply to the AV node i.e. the AV nodal artery . Most of the time this is the right coronary artery . </P> <P> The papillary muscles attach the mitral valve (the valve between the left atrium and the left ventricle) and the tricuspid valve (the valve between the right atrium and the right ventricle) to the wall of the heart . If the papillary muscles are not functioning properly, the mitral valve may leak during contraction of the left ventricle . This causes some of the blood to travel "in reverse", from the left ventricle to the left atrium, instead of forward to the aorta and the rest of the body . This leaking of blood to the left atrium is known as mitral regurgitation . Similarly, the leaking of blood from the right ventricle through the tricuspid valve and into the right atrium can also occur, and this is described as tricuspid insufficiency or tricuspid regurgitation . </P>

Where do coronary arteries begin and veins end