What is the primary function of alveoli in the lungs?

• A. Produce sound
• B. Facilitate gas exchange
• C. Transport oxygen
• D. Filter air

Answer: (B)

The primary function of alveoli in the lungs is to facilitate gas exchange. Alveoli are tiny air sacs located at the end of the respiratory tree and are crucial for the respiratory process. They provide a large surface area for the exchange of oxygen and carbon dioxide between the air in the lungs and the blood in the surrounding capillaries.

During inhalation, oxygen enters the alveoli and diffuses through the thin walls into the bloodstream, where it is picked up by red blood cells for distribution to the body. At the same time, carbon dioxide, which is a waste product of metabolism, diffuses from the blood into the alveoli to be exhaled. This efficient transfer of gases occurs due to the large surface area of the alveoli and their close proximity to the blood vessels.

The other functions described in the options, such as producing sound, transporting oxygen, and filtering air, are associated with different aspects of the respiratory system. For example, sound production primarily involves the larynx, while oxygen transport is carried out by red blood cells in the bloodstream. The filtering of air is mainly a function of the nasal passages and bronchi, where mucus and hairs trap particles before they reach the alveoli. Thus, the unique structure of