How is inhaled air modified before it reaches the lungs?

Options

A. It must be humified.
B. It must be warmed.
C. It must be filtered.
D. All of the above

Answer

To answer the question "How is inhaled air modified before it reaches the lungs?", we can break down the process into several key steps:

### Step-by-Step Solution:

1. **Entry of Air**: Inhaled air enters the body through the nostrils or mouth.

2. **Filtration**:
- As air passes through the nasal passages, it encounters tiny hairs called cilia and mucus.
- These structures act as filters that trap dust, pollen, and other particulate matter, preventing them from entering the lungs.

3. **Humidification**:
- The air is then humidified as it passes through the moist surfaces of the nasal cavity.
- This process adds moisture to the air, which is essential for the respiratory system to function properly and to prevent the lungs from drying out.

4. **Warming**:
- The inhaled air is also warmed to match the body temperature.
- This occurs as the air comes into contact with the warm blood vessels in the nasal passages and trachea, ensuring that the air reaching the lungs is at a suitable temperature for gas exchange.

5. **Final Modification**:
- By the time the air reaches the trachea and subsequently the lungs, it has been filtered, humidified, and warmed.
- This modification is crucial for efficient respiration and to protect the delicate tissues of the lungs.

6. **Conclusion**:
- Therefore, inhaled air is modified in three significant ways: it is filtered, humidified, and warmed.
- The correct answer to the question is that all of these modifications occur before the air reaches the lungs.

### Final Answer:
Inhaled air is modified before it reaches the lungs by being filtered, humidified, and warmed. Thus, the correct answer is option 4: all of the above.

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