What is the primary role of alveoli in the respiratory system?

The primary role of alveoli in the respiratory system is to allow gas exchange with the bloodstream. Alveoli are tiny, balloon-like structures located at the end of the bronchial tubes in the lungs. Their walls are extremely thin and are surrounded by a network of capillaries. This anatomical arrangement creates an ideal environment for the exchange of gases—oxygen is absorbed into the blood, and carbon dioxide is expelled from the blood to be exhaled.

During inhalation, air fills the alveoli, increasing the surface area for gas exchange and maximizing the efficiency of oxygen intake and carbon dioxide removal. This process is vital for maintaining proper blood oxygen levels and is essential for the overall function of the body's cells and organs.

The other options, while related to functions of the respiratory system, do not accurately describe the primary role of alveoli. Transporting air to the trachea is a function of the upper respiratory tract. Sound production involves structures in the larynx and vocal cords, not the alveoli directly. Filtering dust and foreign particles primarily occurs in the nasal passages and upper airways, rather than in the alveoli where gas exchange takes place.