The coronary arteries originate as the right and left main coronary arteries,
which exit the ascending aorta just above the aortic valve (coronary ostia).
There are three cusps of the aortic valve: the non-coronary cusp, which
contains no ostia, the right coronary cusp, which contains the ostia of
the right coronary artery, and the left coronary cusp, which contains the
ostia of the left (main) coronary artery. The ostia of the left and right
coronary arteries are located just above the aortic valve, as are the left
and right sinuses of Valsalva.
Oxygenated blood is pumped into the aorta from the left ventricle; it then
flows into the coronary artery ostia. Blood flow into the coronary arteries
is greatest during ventricular diastole.