Final answer:
The smallest airways in the conducting zone are the terminal bronchioles, which are the last airways before the respiratory zone begins with respiratory bronchioles.
Step-by-step explanation:
The smallest airways in the conducting zone are the terminal bronchioles. The conducting zone of the respiratory system includes all the respiratory passages that serve as conduits for air to reach the sites where gas exchange occurs. The terminal bronchioles then give way to the respiratory zone, which begins with the respiratory bronchioles, and continues with alveolar ducts and alveolar sacs where gas exchange takes place. Thus, the conducting zone ends with terminal bronchioles, which are the last airway passages before the gas exchange region of the lungs.
Each lung contains more than one thousand terminal bronchioles that do not have cartilage in their walls, unlike the larger bronchi. The muscular walls of terminal bronchioles allow them to adjust airflow by contracting or relaxing. These terminal bronchioles then branch into respiratory bronchioles, leading to alveolar ducts, and finally to alveolar sacs, resembling clusters of grapes where the actual gas exchange occurs at the alveoli.