Where does blood drain from the myocardium?

Blood drains from the myocardium primarily through the coronary sinus, which is a large vein that collects deoxygenated blood from the heart muscle itself. The coronary sinus is located on the posterior aspect of the heart and empties directly into the right atrium. This arrangement is crucial because the myocardium, composed of heart muscle, requires a constant supply of oxygenated blood from the coronary arteries. After the blood has delivered its oxygen and nutrients, it needs an efficient way to return to the chambers of the heart for reoxygenation in the lungs. Hence, the deoxygenated blood collected by the coronary sinus flows into the right atrium, allowing for efficient circulation.

The left ventricle, pulmonary trunk, and aorta are involved in the heart's pumping action and distribution of oxygenated blood to the body, but they do not serve as pathways for drainage from the myocardium. Therefore, the correct channel for the drainage of blood from the heart muscle itself is indeed through the coronary sinus into the right atrium.