Which vein drains deoxygenated blood from the heart muscle into the right atrium?

• A. Coronary sinus
• B. Superior vena cava
• C. Inferior vena cava
• D. Pulmonary vein

Answer: (A)

The key idea is how blood from the heart muscle (myocardium) returns to the heart. Veins of the heart drain deoxygenated blood into a large vein called the coronary sinus, which sits in the posterior part of the heart. The coronary sinus then empties into the right atrium, delivering the myocardium’s venous blood to the chamber that sends it to the lungs for oxygenation.

In contrast, the superior and inferior vena cavae collect systemic venous blood from the rest of the body into the right atrium, not blood from the heart muscle itself. The pulmonary veins bring oxygenated blood from the lungs into the left atrium, not into the right atrium. So the vessel that specifically collects deoxygenated blood from the heart muscle and drains into the right atrium is the coronary sinus.