Final answer:
The coronary sinus drains deoxygenated blood from the myocardium and empties into the right atrium of the heart, contributing to the systemic circulation.
Step-by-step explanation:
The coronary sinus empties into the right atrium of the heart. The heart consists of several key structures that manage blood flow in and out of the cardiac chambers. The right atrium serves a crucial role as the receiving chamber for blood returning from the systemic circulation to the heart. This includes the superior and inferior venae cavae, as well as the coronary sinus.
However, most venous blood flow from the coronary veins flows directly into the coronary sinus and from there directly into the right atrium. It is located immediately superior and slightly medial to the opening of the inferior vena cava and is responsible for directing the majority of the blood from the coronary veins back into the heart's right atrium, thus entering the systemic circulation.