What is the primary site of gaseous exchange in the human respiratory system, consisting of tiny air sacs surrounded by capillaries?

💡 Solution & Explanation

Alveoli are microscopic air sacs in human lungs where the actual diffusion of oxygen into pulmonary capillaries and carbon dioxide out of the blood takes place. Conducting passages like the trachea and bronchi only transport air and do not participate in respiratory gas exchange. The extremely thin walls of millions of alveoli provide a vast surface area essential for efficient respiration.