Kaplan Nursing Entrance Exam Practice 2026 – Comprehensive Prep

The small air passages within the lungs that further transport air are called bronchioles. These structures branch off from the larger bronchi and become progressively smaller, leading to the alveoli, where gas exchange occurs. Bronchioles have a diameter less than one millimeter and lack cartilage, consisting instead of smooth muscle that allows for the regulation of airflow into the alveoli. This unique structure plays a crucial role in the respiratory system by ensuring that air is delivered efficiently to the sites of gas exchange in the lungs.

The other choices refer to different components of the respiratory system: the alveoli are tiny air sacs where oxygen and carbon dioxide exchange occurs; the trachea is the main airway leading into the lungs; and the bronchi are the larger passages that branch off from the trachea into each lung. Understanding the function and structure of each of these components is essential for a comprehensive grasp of respiratory physiology.