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In page Coronary artery anomaly:

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Coronary arteries arise from ostia, openings of the aorta (the largest artery in the human body) at the upper third or middle third of the sinuses of Valsalva (the first part of the big pipe coming off the main pumping chamber). The walls of coronary arteries consist of three layers: the tunica intima or inner layer (possible site of lipid deposits and fibrosis, during life), the tunica media (a smooth muscle layer whose tone is modulated by the nervous system, influencing vessel diameter and resistance) and adventitia (where nervous endings are located). Normally, the initial portion of coronary arteries lies onto the external surface of the heart (epicardium) where fat deposits tend to form during life.[citation needed]