Which of the following structures are absent in the heart of adult humans?

Options

A. Ductus arteriosus
B. Ligamentum arteriosus
C. Fossa ovalis
D. Columnae carneae

Answer

To determine which structures are absent in the heart of adult humans, let's analyze the provided options step by step:

1. **Identify the Structures**: The options provided are:
- Ductus arteriosus
- Ligamentum arteriosus
- Fossa ovalis
- Chordae tendineae

2. **Understand Each Structure**:
- **Ductus Arteriosus**: This is a fetal blood vessel that connects the pulmonary artery to the aorta, allowing blood to bypass the lungs. After birth, it typically closes and becomes a fibrous remnant.
- **Ligamentum Arteriosus**: This is the remnant of the ductus arteriosus after it closes. It is present in adults.
- **Fossa Ovalis**: This is a depression in the right atrium that is the remnant of the foramen ovale, which allows blood to bypass the lungs in fetal life. It is present in adults as a depression.
- **Chordae Tendineae**: These are fibrous cords that connect the papillary muscles to the atrioventricular valves (mitral and tricuspid valves) in both ventricles. They are present in adults.

3. **Determine Which Structure is Absent**:
- The **ductus arteriosus** is present in the fetal heart but typically closes after birth and is not present in the adult heart. It becomes the ligamentum arteriosus.

4. **Conclusion**: The structure that is absent in the heart of adult humans is the **ductus arteriosus**.

### Final Answer:
The structure that is absent in the heart of adult humans is the **ductus arteriosus**.

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