This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
All open coronary sinus except? 
Select and explain. 
A. Middle cardiac vein, B. Anterior cardiac vein, C. Small cardiac vein, D. Great cardiac vein
B: Anterior cardiac vein
Answer: B: Anterior cardiac vein 
Explanation: Ans. B. Anterior cardiac veinThe coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle. The coronary sinus drains into the right atrium, at the coronary sinus orifice, an opening between the inferior vena cava and the tricuspid valve. It returns blood from the heart muscle, and is protected by a semicircular fold, the valve of coronary sinus (Thebesian valve).