Final answer:
The coronary sinus, located in the coronary sulcus on the posterior of the heart, receives most of the deoxygenated blood from the myocardium and drains directly into the right atrium.
Step-by-step explanation:
The structure located in the coronary sulcus on the posterior of the heart that receives most of the deoxygenated blood from the myocardium is known as the coronary sinus. This large, thin-walled vein lies within the atrioventricular sulcus and directly drains into the right atrium. The coronary veins, which follow the path of the heart's arteries, feed into the coronary sinus, completing the circuit of blood through the heart's own vascular system. The part of the heart that receives most of the deoxygenated blood from the myocardium is the coronary sinus, which is located in the coronary sulcus on the posterior of the heart. The coronary sulcus is the sulcus that marks the boundary between the atria and ventricles.