Cardiac veins drain into which vessel located within the right atrium?

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

Answer: (A)

Cardiac veins drain into a single large venous channel called the coronary sinus. This vessel sits in the posterior part of the heart within the coronary sulcus and collects deoxygenated blood from the heart muscle via tributaries like the great, middle, and small cardiac veins, then empties into the right atrium. The other vessels mentioned have different roles: the superior and inferior vena cavae return systemic venous blood to the right atrium, not the myocardium’s venous blood; the pulmonary veins bring oxygenated blood from the lungs into the left atrium. So, the vessel located within the right atrium that receives the cardiac veins is the coronary sinus.