What are alveoli primarily responsible for?

• A. Producing surfactant
• B. Engaging in gas exchange between blood and air
• C. Transporting carbon dioxide
• D. Transporting oxygen effectively

Answer: (B)

Alveoli are tiny, balloon-like structures in the lungs that play a crucial role in the respiratory system. They are primarily responsible for facilitating gas exchange between the air and the bloodstream. This process occurs through the thin alveolar walls, which allow oxygen from inhaled air to diffuse into the blood while simultaneously enabling carbon dioxide, a waste product of metabolism, to move from the blood into the alveoli to be exhaled.

The process of gas exchange is vital for maintaining adequate oxygen levels in the body, which is necessary for cellular respiration and overall metabolic function. Each alveolus is surrounded by a network of capillaries, where this exchange occurs efficiently due to the large surface area provided by millions of alveoli in the lungs.

While alveoli also play a role in the production of surfactant—which helps keep them open and reduces surface tension—this function does not encompass their main role. Similarly, alveoli do not directly transport carbon dioxide or oxygen; instead, they provide the site where these gases can diffuse between the air and blood, making gas exchange their primary responsibility.