What nourishes the myocardium?

The myocardium, which is the muscular layer of the heart responsible for its contraction and overall function, receives its nourishment primarily through the coronary arteries. These arteries branch off from the aorta shortly after the aorta exits the heart. Their primary role is to supply oxygen-rich blood to the heart muscle itself, ensuring that it receives the necessary nutrients and oxygen required for its demanding work of pumping blood throughout the body.

The pulmonary arteries are responsible for carrying deoxygenated blood from the heart to the lungs, where it gets oxygenated. The venous system works to return deoxygenated blood back to the heart but does not supply nutrients to the myocardium. The aorta, while it is the largest artery in the body and distributes oxygenated blood to the systemic circulation, does not directly nourish the heart muscle. Thus, the correct answer emphasizes the importance of the coronary arteries in maintaining the health and function of the myocardium.