The coronary arteries usually arise from the right and left sinus of Valsalva above the corresponding aortic valve leaflet. Rarely a coronary arises from the pulmonary artery (both arising from the pulmonary artery results in death in infancy). There are several occasional variations in coronary origin, with the left coronary being more variable than the right: the anterior interventricular and circumflex may have separate origins in the left coronary sinus (a); the circumflex may arise from the right (b); both coronaries may arise from the right sinus (c); both coronaries may arise from a single trunk (d); rarely, there may be more than two vessels.
In the majority (~60%) of individuals, the right coronary is the dominant supplier of blood to the heart. In some individuals (~20%), the left system is dominant, with the circumflex continuing as the posterior interventricular. In the rest of the population, the two sides are equally balanced. The sinoatrial node receives its blood supply from the right coronary artery in about 70% of individuals and the atrioventricular node almost always (90%) receives its blood supply from the right.
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