What is the primary function of the alveoli in the lungs?

• A. Production of mucus
• B. Gas exchange
• C. Air filtration
• D. Sound production

Answer: (B)

The primary function of the alveoli in the lungs is gas exchange. Alveoli are tiny air sacs that are surrounded by capillaries, which are the smallest blood vessels. When air enters the lungs, it reaches the alveoli where oxygen from the inhaled air diffuses across the alveolar membrane into the bloodstream. At the same time, carbon dioxide, which is a waste product of metabolism, diffuses from the blood into the alveoli to be exhaled. This process of exchanging oxygen and carbon dioxide is essential for maintaining proper oxygen levels in the blood and removing carbon dioxide.

The structure of the alveoli, with their large surface area and thin walls, facilitates efficient gas exchange. This is critical for breathing and supports cellular respiration throughout the body.