Which term refers to the smallest branches of the bronchi?

The term that refers to the smallest branches of the bronchi is bronchioles. Bronchioles are the thin, small tubes that extend from the bronchi into the lungs and lead to the alveoli, where gas exchange occurs. They play a crucial role in directing airflow to the alveoli and can constrict or dilate to regulate air passage.

Capillaries, while involved in gas exchange, are not part of the bronchial tree and instead are tiny blood vessels that surround the alveoli. Alveoli are the small air sacs at the end of the bronchioles where oxygen and carbon dioxide are exchanged but are not branches of the bronchi themselves. The bronchi are larger airways that branch off from the trachea and lead into the lungs, making them distinct from the bronchioles. Thus, understanding the hierarchical structure of the respiratory system clarifies why bronchioles are identified as the smallest branches of the bronchi.