Which vessel returns blood from the heart muscle to the right atrium?

• A. Coronary sinus
• B. Aorta
• C. Pulmonary artery
• D. Inferior vena cava

Answer: (A)

The heart’s own venous drainage returns blood from the muscle of the heart through a single large vein that empties into the right atrium. This vessel, the coronary sinus, collects deoxygenated blood from the myocardial veins (like the great cardiac vein and others) and delivers it into the right atrium, close to where the vena cavae drain. That setup keeps the blood from the heart muscle circulating back into the right-sided heart chambers before it moves on to the lungs for reoxygenation.

The other vessels described aren’t involved in draining the heart muscle. The aorta is the main arterial outflow to the body, not a vein. The pulmonary artery carries blood from the right ventricle to the lungs, also not a venous drainage vessel. The inferior vena cava brings systemic venous blood from the lower body into the right atrium, not blood from the heart muscle itself.