Basic and Clinical Sciences (BCSE) Practice Exam

What role do alveoli play in gas exchange?

1. They are the primary sites for gas exchange through diffusion.

2. They prevent gas from entering the lungs.

3. They store oxygen for future use.

4. They act as a barrier for pathogens.

The correct answer is: They are the primary sites for gas exchange through diffusion.

Alveoli are crucial structures in the respiratory system that facilitate gas exchange between the air and the blood. They are microscopic air sacs located at the end of the bronchial tree and are primarily responsible for the exchange of oxygen and carbon dioxide. The walls of the alveoli are extremely thin, allowing for efficient diffusion of gases. Oxygen from the inhaled air passes through the alveolar walls and into the surrounding capillaries, where it binds to hemoglobin in red blood cells. Similarly, carbon dioxide in the blood diffuses into the alveoli to be exhaled. This function is essential for maintaining the body's oxygen levels and removing carbon dioxide, which is a waste product of metabolism. The structure of the alveoli, with their large surface area and extensive network of capillaries, is specifically adapted to maximize this gas exchange process.