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

**Step-by-Step Solution:**

1. **Understanding the Structure of Bronchioles:**
- The bronchioles are small air passages in the respiratory system that lead to the alveoli. They have a diameter of less than 1.5 millimeters and do not have the same structural support as larger airways.

2. **Role of Cartilage in the Respiratory System:**
- In the trachea and bronchi, cartilage rings and plates provide structural support to keep these airways open. The trachea has complete cartilage rings, while the bronchi have incomplete cartilage plates.

3. **Bronchioles and Structural Support:**
- Unlike the trachea and bronchi, bronchioles do not have cartilage rings. Instead, they rely on the surrounding lung tissue and the pressure differences within the lungs to maintain their shape and prevent collapse.

4. **Transpulmonary Pressure:**
- The key factor that prevents the bronchioles from collapsing is the transpulmonary pressure. This pressure is the difference between the pressure inside the alveoli and the pressure in the pleural cavity. It helps keep the bronchioles open during breathing.

5. **Evaluating the Options:**
- **Presence of Lecithin:** This is incorrect as lecithin is a type of fat and does not provide structural support to bronchioles.
- **Presence of Incomplete Cartilaginous Rings:** This is also incorrect because bronchioles do not have cartilage rings; they have smooth muscle and elastic fibers instead.
- **Presence of Complete Cartilaginous Rings:** This is incorrect since complete rings are found in the trachea, not in bronchioles.
- **Presence of Mucus:** While mucus plays a role in trapping particles and keeping airways moist, it does not prevent bronchioles from collapsing.

6. **Conclusion:**
- The correct answer is that bronchioles do not collapse due to the transpulmonary pressure that keeps them expanded, not due to cartilage or mucus.

**Final Answer:**
The bronchioles do not collapse when there is no air due to the transpulmonary pressure that keeps them expanded.

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