Which valve is present at the opening of coronary sinus?

Options

A. Mitral valve
B. Eustachian valve
C. Thebesian valve
D. Tricuspid valve

Answer

To answer the question "Which valve is present at the opening of the coronary sinus?", we can follow these steps:

1. **Understand the Structure**: The coronary sinus is a large vein that collects deoxygenated blood from the heart muscle (myocardium) and drains it into the right atrium.

2. **Identify the Location**: The coronary sinus opens into the right atrium of the heart.

3. **Know the Function**: The function of the valve at the opening of the coronary sinus is to prevent the backflow of blood from the right atrium into the coronary sinus when the right atrium contracts.

4. **Identify the Valve**: The valve that guards the opening of the coronary sinus is known as the Thebesian valve (or valve of Thebesius).

5. **Conclusion**: Therefore, the valve present at the opening of the coronary sinus is the Thebesian valve.

### Final Answer:
The valve present at the opening of the coronary sinus is the Thebesian valve.