Which of the folllowing structures prevents atrioventricular valves from reverting into atria during ventricular contraction?

Options

A. Chordae tendine
B. Purkinje fibers
C. Bundle of His
D. Columnae carnae

Answer

To solve the question, "Which of the following structures prevents atrioventricular valves from reverting into atria during ventricular contraction?", we will analyze the options provided and understand the function of each structure in relation to the atrioventricular (AV) valves.

### Step-by-Step Solution:

1. **Understanding Atrioventricular Valves**: The atrioventricular valves, also known as AV valves, are located between the atria and ventricles of the heart. Their primary function is to prevent the backflow of blood from the ventricles into the atria during ventricular contraction.

2. **Identifying the Structures**: The options provided are:
- A) Chordae tendineae
- B) Purkinje fibers
- C) Bundle of His
- D) Columnar carneae

3. **Analyzing Each Option**:
- **A) Chordae tendineae**: These are fibrous cords that connect the AV valves to the papillary muscles in the ventricles. They play a crucial role in preventing the leaflets of the AV valves from inverting into the atria when the ventricles contract.
- **B) Purkinje fibers**: These fibers are responsible for conducting electrical impulses that trigger ventricular contraction, but they do not prevent the AV valves from reverting.
- **C) Bundle of His**: This structure is part of the electrical conduction system of the heart, transmitting impulses to the ventricles, but it does not have a role in preventing backflow through the AV valves.
- **D) Columnar carneae**: These are muscular ridges found in the ventricles that help in the contraction of the heart muscle but do not prevent the AV valves from inverting.

4. **Conclusion**: The structure that prevents the atrioventricular valves from reverting into the atria during ventricular contraction is the **chordae tendineae**. They ensure that the valve leaflets remain in place and do not allow backflow of blood.

### Final Answer:
The correct answer is **A) Chordae tendineae**.