Which of the following are in direct contact with the AV valves and prevent these from collapsing back into atria ?

Options

A. Chordae tendinae
B. Papillary muscles
C. Columnae carnae
D. Musculi pentinati

Answer

To solve the question regarding which structures are in direct contact with the AV valves and prevent them from collapsing back into the atria, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding AV Valves**: The Atrioventricular (AV) valves are located between the atria and ventricles of the heart. They are crucial for ensuring unidirectional blood flow.

2. **Identifying Key Structures**: The question provides four options:
- Chordae tendineae
- Papillary muscle
- Columnar carnea
- Musculi pectinate

3. **Role of Chordae Tendineae**: The chordae tendineae are fibrous cords that connect the AV valves to the papillary muscles. Their primary function is to prevent the valves from inverting or collapsing back into the atria when the ventricles contract.

4. **Role of Papillary Muscles**: While the papillary muscles are connected to the chordae tendineae and play a supportive role, they do not directly contact the AV valves.

5. **Understanding Other Options**:
- **Columnar carnea**: These are muscular structures found in the ventricles and do not have a direct role in supporting the AV valves.
- **Musculi pectinate**: These are muscular ridges found in the atria and also do not have a direct role in supporting the AV valves.

6. **Conclusion**: The only structure that is in direct contact with the AV valves and prevents them from collapsing back into the atria is the **chordae tendineae**.

### Final Answer:
**Chordae tendineae** are in direct contact with the AV valves and prevent them from collapsing back into the atria.

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