Most cardiac veins drain into which structure before delivering blood to the right atrium?

• A. Great cardiac vein
• B. Coronary sinus
• C. Anterior interventricular artery
• D. Oblique vein of left atrium

Answer: (B)

Most cardiac venous blood is collected into the coronary sinus, a large venous channel located in the posterior part of the coronary sulcus. This single structure gathers blood from the major cardiac veins and then empties into the right atrium, providing the main route for venous return from the heart muscle. While some smaller veins may drain directly into other chambers or have smaller tributaries, the coronary sinus serves as the primary convergence point before blood reaches the right atrium. The anterior interventricular artery is an artery, not a vein, so it isn’t involved in venous drainage, and the oblique vein of the left atrium is a smaller contributor that typically drains into the coronary sinus but does not serve as the main collection point.