The blood supply to the heart is divided into two main arteries which lie in the interventricular and atrioventricular grooves:
The right coronary artery, smaller than the left, arises from the anterior aortic sinus. Then it passes between the pulmonary trunk and the right atrium descending into the inferior border of the heart along the interventricular groove to anastomose with the left coronary artery at the posterior interventricular groove. At the lower border of the heart, it gives off the right marginal branch and the posterior interventricular branch which runs in the posterior interventricular groove. The posterior interventricular branch then anastomoses with the left coronary artery near the apex of the heart.
The left coronary artery arises from the left posterior aortic sinus. It passes posterior to the left side of the pulmonary trunk to reach the left part of the atrioventricular groove. Then it crosses laterally on the left border of the heart to form the circumflex artery that extends to the posterior interatrial groove. The left coronary artery gives off an important branch about 2 cm from its origin, the anterior interventricular artery which supplies the anterior aspect of both ventricles. This then passes around the apex of the heart to anastomose with the posterior interventricular branch of the right coronary artery.
Figure.8: The coronary arteries (Drake et al, 2009).
The venous drainage of the heart (Fig.9):
The cardiac veins run alongside the coronary arteries and eventually open into the right atrium. The rest of the blood drains by small cardiac veins directly into the cardiac chambers.
In the posterior of the atrioventricular groove runs the coronary sinus which into the right atrium: the opening is located to the left of that of the inferior vena cava. The coronary sinus receives blood from four main veins:
1- The great cardiac vein which runs in the anterior interventricular groove.
2- The middle cardiac vein which runs in the posterior interventricular groove.
3- The small cardiac vein which runs with the right marginal artery along the lower border of the heart.
4- The oblique vein which passes obliquely across the posterior left atrium.
The anterior cardiac veins open directly into the right atrium by crossing the anterior atrioventricular groove, draining the blood from the anterior surface of the heart.
Figure.9: The venous drainage of the heart (Drake et al, 2009).