What is the physiological role of the alveoli in the lungs?

The alveoli are tiny air sacs located at the end of the respiratory bronchioles in the lungs, and their primary physiological role is to facilitate gas exchange. This process is crucial for respiration, as it allows the exchange of oxygen and carbon dioxide between the air we breathe and the bloodstream.

When air reaches the alveoli, oxygen diffuses across the thin walls of these sacs into the adjacent capillaries, where it binds to hemoglobin in red blood cells. Simultaneously, carbon dioxide, which is a waste product of metabolism, diffuses from the blood into the alveoli to be expelled from the body during exhalation. The structure of the alveoli—specifically their large surface area and thin walls—optimizes this gas exchange process, making it highly efficient.

The other options do not accurately describe the primary function of the alveoli. For instance, while the lungs play a role in filtering some particles from the air, this function is more associated with the upper airways and other structures, rather than the alveoli themselves. Sound production for speech primarily involves the vocal cords in the larynx, not the alveoli. Airflow control is managed by various muscles and structures in the respiratory system, such as the diaphragm and