Which structures branch from the bronchi?

The correct answer is bronchioles, as they are the structures that branch from the bronchi. In the respiratory system, after air travels through the trachea, it enters the bronchi, which then divide into smaller passages known as bronchioles. These bronchioles continue to branch out into even finer networks, ultimately leading to the alveoli, where gas exchange occurs.

Bronchioles are crucial as they help direct airflow into the lungs and play a role in regulating airflow through their muscular walls, which can constrict or dilate. This branching structure is essential for increasing the surface area for gas exchange and ensuring that air reaches the alveoli effectively.

Other structures mentioned, such as alveoli and capillaries, have their specific functions within the respiratory system. Alveoli are the air sacs where oxygen and carbon dioxide exchange takes place, and capillaries are the tiny blood vessels that surround the alveoli, transporting gases to and from the bloodstream. Bronchial tubes generally refer to the larger airway passages but do not accurately capture the smaller, branching tubes that follow from the bronchi.