The number of alveoli in the human lungs has been estimated to be approximately

Options

A. 100 million
B. 300 million
C. 125 million
D. 300 billion

Answer

To answer the question regarding the estimated number of alveoli in the human lungs, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Function of Alveoli**:
- Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place. Their primary function is to facilitate this gaseous exchange efficiently.

2. **Structure of Alveoli**:
- Alveoli are irregularly shaped and clustered, which increases the surface area available for gas exchange. This is crucial because a larger surface area allows for more efficient diffusion of gases.

3. **Thin Membranes**:
- The walls of the alveoli are very thin, which further enhances the efficiency of gas exchange. Thin membranes allow gases to move quickly between the alveoli and the blood.

4. **Rich Blood Supply**:
- Alveoli have a rich blood supply, which is essential for transporting oxygen to body tissues and removing carbon dioxide from the bloodstream.

5. **Estimation of Alveoli Count**:
- It has been estimated that there are approximately 300 million alveoli in the human lungs. This number is significant as it provides a vast surface area for gas exchange, which is necessary for meeting the oxygen demands of the body.

6. **Conclusion**:
- Therefore, the estimated number of alveoli in the human lungs is around 300 million, or 30 crore. This high number is essential for maximizing the efficiency of gas exchange.

### Final Answer:
The number of alveoli in the human lungs has been estimated to be approximately **300 million**.

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