Which of the following best defines the function of alveoli?

The function of alveoli primarily revolves around facilitating gas exchange, which is vital for the respiratory process. Alveoli are tiny, balloon-like structures located at the ends of the bronchioles in the lungs. They provide a large surface area for gas exchange to occur between the air we breathe in and the blood within the capillaries that surround them.

During inhalation, oxygen from the air fills the alveoli, and it diffuses across the alveolar membrane into the bloodstream, where it binds to hemoglobin in red blood cells. Simultaneously, carbon dioxide, which is a waste product of metabolism in the body, diffuses from the blood into the alveoli to be exhaled. This efficient exchange of gases is critical for maintaining the body’s oxygen levels and removing carbon dioxide, thereby sustaining cellular respiration and overall metabolic processes.

While protecting the lungs from infection, maintaining lung structure, and transporting oxygen are important functions related to respiratory health, they do not directly represent the primary role of the alveoli. The alveoli's unique structure and extensive surface area are specifically designed to optimize the gas exchange process, making it their primary function.