Presence of large number of alveoli around alveolar ducts opening into bronchioles in mammalian lungs is

Options

A. an efficient system of ventilation with no residual air
B. an efficient system of ventilation with little residual air
C. inefficient system of ventilation with little of residual air
D. inefficient system of ventilation with high percentage of residual air

Answer

To solve the question regarding the presence of a large number of alveoli around alveolar ducts opening into bronchioles in mammalian lungs, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of the Respiratory System**:
- The respiratory system begins with the trachea, which bifurcates into primary bronchi. These further divide into secondary bronchi, tertiary bronchi, and eventually lead to bronchioles.

2. **Role of Alveoli**:
- Alveoli are tiny air sacs located at the end of the bronchioles. They are the primary site for gas exchange in the lungs.

3. **Features of Alveoli**:
- Alveoli have a **large surface area** (approximately 100 square meters in total) which facilitates efficient gas exchange.
- They consist of a **thin single layer of epithelial cells**, allowing for easy diffusion of gases (oxygen and carbon dioxide).
- Alveoli are surrounded by a dense network of **capillaries**, ensuring a rich blood supply for gas exchange.

4. **Importance of Ventilation**:
- An efficient ventilation system is crucial for maintaining a concentration gradient for gas exchange. This means that fresh air must continuously enter the alveoli to replace air that has already participated in gas exchange.

5. **Dead Space**:
- There is a volume of air in the lungs that does not participate in gas exchange, known as **dead space**. This air remains in the respiratory system but does not contribute to oxygen uptake or carbon dioxide removal.

6. **Conclusion**:
- The presence of a large number of alveoli around the alveolar ducts is essential for creating an efficient system of ventilation with minimal residual air. This design maximizes the surface area available for gas exchange while maintaining effective ventilation.

### Final Answer:
The presence of a large number of alveoli around alveolar ducts opening into bronchioles in mammalian lungs is to create an efficient system of ventilation with little residual air.

---