Physiologic Anatomy of the Coronary Blood Supply
Figure 21–3 shows the heart and its coronary blood supply. Note that the main coronary arteries lie on the surface of the heart and smaller arteries then pene-trate from the surface into the cardiac muscle mass. It is almost entirely through these arteries that the heart receives its nutritive blood supply. Only the inner 1/10 millimeter of the endocardial surface can obtain sig-nificant nutrition directly from the blood inside the cardiac chambers, so that this source of muscle nutri-tion is minuscule.
The left coronary artery supplies mainly the anterior and left lateral portions of the left ventricle, whereas the right coronary arterysupplies most of the right ventricle as well as the posterior part of the left ven-tricle in 80 to 90 per cent of people.
Most of the coronary venous blood flow from the left ventricular muscle returns to the right atrium of the heart by way of thecoronary sinus—which is about 75 per cent of the total coronary blood flow. And most of the coronary venous blood from the right ventricu-lar muscle returns through small anterior cardiac veins that flow directly into the right atrium, not by way of the coronary sinus. A very small amount of coronary venous blood also flows back into the heart through very minute thebesian veins, which empty directly into all chambers of the heart.