<P> There are some anastomoses between branches of the two coronary arteries . However the coronary arteries are functionally end arteries and so these meetings are referred to as potential anastamoses, which lack function, as opposed to true anastomoses like that in the palm of the hand . This is because blockage of one coronary artery generally results in death of the heart tissue due to lack of sufficient blood supply from the other branch . When two arteries or their branches join, the area of the myocardium receives dual blood supply . These junctions are called anastomoses . If one coronary artery is obstucted by an atheroma, the second artery is still able to supply oxygenated blood to the myocardium . However, this can only occur if the atheroma progresses slowly, giving the anastomoses a chance to proliferate . </P> <P> Under the most common configuration of coronary arteries, there are three areas of anastomoses . Small branches of the LAD (left anterior descending / anterior interventricular) branch of the left coronary join with branches of the posterior interventricular branch of the right coronary in the interventricular sulcus (groove). More superiorly, there is an anastomosis between the circumflex artery (a branch of the left coronary artery) and the right coronary artery in the atrioventricular groove . There is also an anastomosis between the septal branches of the two coronary arteries in the interventricular septum . The photograph shows area of heart supplied by the right and the left coronary arteries . </P> <P> The left and right coronary arteries occasionally arise by a common trunk, or their number may be increased to three; the additional branch being the posterior coronary artery (which is smaller in size). In rare cases, a person will have the third coronary artery run around the root of the aorta . </P> <P> Occasionally, a coronary artery will exist as a double structure (i.e. there are two arteries, parallel to each other, where ordinarily there would be one). </P>

Where does blood from the coronary circulation return to the heart