which of the following is the primary site of exchange of gases in the human lungs?

Options

A. Alveoli
B. Secondary bornchi
C. Tertiary bornchi
D. Bronchioles

Answer

To determine the primary site of gas exchange in the human lungs, we can follow these steps:

### Step 1: Understand the Structure of the Lungs
The human lungs consist of two main parts, and within them, there are various branching structures that facilitate the movement of air. The trachea, or windpipe, enters the lungs and divides into two primary bronchi.

**Hint:** Think about the pathway that air takes as it enters the lungs.

### Step 2: Identify the Branching of the Bronchi
After the primary bronchi, the airways continue to branch into secondary bronchi and then tertiary bronchi. These branches further divide into smaller air passages known as bronchioles.

**Hint:** Consider how the bronchioles connect to the areas where gas exchange occurs.

### Step 3: Locate the Alveoli
At the end of the bronchioles, there are tiny air sacs called alveoli. These structures are cup-shaped and are surrounded by capillaries, which are small blood vessels.

**Hint:** Focus on the structures that are specifically designed for gas exchange.

### Step 4: Understand the Function of Alveoli
The alveoli are the primary sites where the exchange of gases occurs. They allow oxygen to enter the bloodstream and carbon dioxide to be expelled from the blood. This process is essential for respiration.

**Hint:** Think about the role of alveoli in oxygenating the blood and removing carbon dioxide.

### Step 5: Conclusion
Based on the structure and function of the lungs, the primary site of gas exchange in the human lungs is the alveoli.

**Final Answer:** Alveoli