When there is no air in initial bronchioles, they does not collapse. It is due to `:`

Options

A. Presence of Lecithin
B. Presence of incomplete cartilagenous rings
C. Presence of complete cartilagenous rings
D. Presence of mucous

Answer

To solve the question, "When there is no air in initial bronchioles, they do not collapse. It is due to:", we will analyze the options provided and the physiological structure of the bronchioles.

### Step-by-Step Solution:

1. **Understanding the Structure of Bronchioles**:
- The bronchioles are small air passages in the lungs that lead from the bronchi to the alveoli. They are involved in the conduction of air and gas exchange.

2. **Analyzing the Options**:
- The options provided are:
a) Presence of lecithin
b) Presence of incomplete cartilage rings
c) Presence of complete cartilaginous rings
d) Presence of mucus

3. **Evaluating Each Option**:
- **Presence of Lecithin**: Lecithin is a phospholipid that is part of surfactant, which reduces surface tension in the alveoli but does not directly prevent collapse of bronchioles.
- **Presence of Incomplete Cartilage Rings**: The bronchi have incomplete cartilage rings that allow flexibility and prevent collapse. This is particularly important in the trachea and bronchi, where some collapse is necessary for food passage in the esophagus.
- **Presence of Complete Cartilaginous Rings**: Complete rings would not allow for flexibility and would not be present in the bronchioles.
- **Presence of Mucus**: Mucus helps trap particles and pathogens but does not provide structural support to prevent collapse.

4. **Conclusion**:
- The correct answer is **b) Presence of incomplete cartilage rings**. These rings provide structural support to the bronchioles, preventing them from collapsing even when there is no air present.

### Final Answer:
When there is no air in initial bronchioles, they do not collapse due to the presence of **incomplete cartilage rings**.

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