<Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> Coronary circulation is the circulation of blood in the blood vessels of the heart muscle (myocardium). The vessels that deliver oxygen - rich blood to the myocardium are the coronary arteries . The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins . These include the great cardiac vein, the middle cardiac vein, the small cardiac vein, the smallest cardiac veins, and the anterior cardiac veins . </P> <P> The arteries, when healthy, are capable of autoregulation to maintain coronary blood flow at levels appropriate to the needs of the heart muscle . These relatively narrow vessels are commonly affected by atherosclerosis and can become blocked, causing angina or a heart attack . The coronary arteries that run deep within the myocardium are referred to as subendocardial . </P> <P> The coronary arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium; there is very little redundant blood supply, which is why blockage of these vessels can be so critical . </P>

When does blood flow occur through the coronary circulation