The alveoli are the primary sites of gas exchange in the lungs, marking them as the key components of the respiratory zone. This zone includes structures where oxygen and carbon dioxide diffuse between air and blood, crucial for effective respiration. In contrast, the trachea, bronchi, and terminal bronchioles belong to the conducting zone, responsible mainly for air transport and conditioning. Understanding the distinction is vital during surgical procedures involving lung resection or ventilation management to preserve or recognize functional lung tissue.

Reference: Gray's Anatomy, Richard L. Drake, 42nd Edition.