The conus artery (third coronary artery) is a coronary artery that is present in only 45 percent of human hearts. The conus artery may provide collateral blood flow to the heart when the left anterior descending artery is occluded. In one study, 305 cadaveric specimens were examined to determine the origin of the conus coronary artery. The authors found that the conus artery could arise independently from the aorta or from a common ostium with the right coronary artery.
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Conus artery Wikipedia(Text) CC BY-SA