Final answer:
Bronchioles are the series of small tubules branching from the smallest bronchi inside each lung, carrying air to alveolar ducts and alveolar sacs for gas exchange.
Step-by-step explanation:
The series of small tubules branching from the smallest bronchi inside each lung are known as bronchioles. The respiratory system includes a very important relationship among the bronchi, bronchial tubes, and bronchioles, as they carry air to and from the lungs. This pathway ensures that the air is warmed, moistened, and filtered before reaching the terminal bronchioles, which are connected to alveolar ducts and alveolar sacs, where gas exchange takes place. The bronchioles play a crucial role by controlling the flow of air to the alveoli, and their muscular walls, which lack cartilage, can adjust the airway size.