Which feature of alveoli is critical for efficient gas exchange?

The extensive surface area of alveoli is critical for efficient gas exchange because it maximizes the amount of oxygen that can diffuse into the blood and carbon dioxide that can be removed from it. Alveoli are tiny, balloon-like structures in the lungs that significantly increase the surface area available for gas exchange. This large surface area allows for a greater number of gas molecules to be exchanged simultaneously, which is essential for meeting the oxygen demands of the body and expelling carbon dioxide efficiently.

Additionally, the thin walls of the alveoli (one cell thick) facilitate rapid diffusion of gases due to a short distance for gas molecules to travel. The extensive surface area, combined with this thin barrier, creates an ideal environment for gas exchange, ensuring that the respiratory system can function effectively.