It is the component of systemic circulation, which is responsible for the drainage of blood to and from the cardiac musculature.
The aorta gives rise to two coronary arteries (right and left), just beyond the opening of the semilunar valves.
During diastole, the blood is forced into the coronary arteries, which then supply it to the entire cardiac muscle tissue.
The deoxygenated blood is drained back into the right atrium via the coronary veins.
Most of the coronary veins join together to form the coronary venous sinus.
Sometimes, a subtotal/complete obstruction of the coronary arteries deprives the heart tissue of oxygenated blood, which may lead to the death of the heart muscle (myocardial infarction).