Which part of the respiratory system is primarily responsible for gas exchange?

• A. Bronchi
• B. Trachea
• C. Alveoli
• D. Larynx

Answer: (C)

The alveoli are the primary structures in the respiratory system responsible for gas exchange. These tiny, balloon-like sacs are located at the end of the bronchioles in the lungs and are surrounded by a network of capillaries. The alveoli provide a large surface area and a thin barrier for oxygen and carbon dioxide to diffuse between the air in the alveoli and the blood in the capillaries. When inhaled air reaches the alveoli, oxygen from the air passes into the bloodstream, and carbon dioxide from the blood is expelled into the alveolar air, which is then exhaled. This efficient exchange of gases is crucial for maintaining proper oxygen levels in the body and removing carbon dioxide, a waste product of metabolism.

In contrast, the bronchi and trachea primarily serve as conduits for air, directing it from the trachea into the lungs and vice versa. The larynx functions mainly as a passage for air and plays a role in voice production, but it is not involved in the gas exchange process. Thus, the alveoli's unique structure and placement make them essential for effective gas exchange in the respiratory system.