Which structure of lungs is directly involved in `O_(2)//CO_(2)` exchange between air and blood capillaries?

Options

A. Bronchi
B. Trechea
C. Alveoli
D. Secondary bronchi

Answer

To determine which structure of the lungs is directly involved in the exchange of oxygen (O₂) and carbon dioxide (CO₂) between air and blood capillaries, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structures of the Respiratory System**:
- The main structures involved in the respiratory system include the trachea, bronchi, bronchioles, and alveoli.

2. **Understand the Function of Each Structure**:
- **Trachea**: The windpipe that conducts air to the bronchi but is not involved in gas exchange.
- **Bronchi**: The main passageways that branch from the trachea into the lungs, also not directly involved in gas exchange.
- **Bronchioles**: Smaller branches of the bronchi that lead to the alveoli, but still not the primary site for gas exchange.
- **Alveoli**: Tiny air sacs located at the end of the bronchioles where gas exchange occurs.

3. **Focus on Gas Exchange**:
- Gas exchange refers to the process where oxygen from the air is transferred to the blood, and carbon dioxide from the blood is released into the air. This process occurs in the alveoli.

4. **Analyze the Structure of Alveoli**:
- Alveoli are made up of simple squamous epithelium, which consists of very thin and flattened cells. This thin structure allows for efficient diffusion of gases.
- Alveoli are surrounded by capillaries, facilitating the exchange of gases between the air in the alveoli and the blood in the capillaries.

5. **Conclude**:
- Based on the above analysis, the structure of the lungs that is directly involved in the exchange of O₂ and CO₂ between air and blood capillaries is the **alveoli**.

### Final Answer:
The structure of the lungs directly involved in O₂/CO₂ exchange between air and blood capillaries is **alveoli**.

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