In the respiratory system certain structures allow air to pass from the trachea to the lungs. They are lined with thin muscles and coated with epithelial cells. These structures are called bronchial tubes.
alveoli.
bronchioles.
lobules.

A. Bronchial Tubes

Explanation:

When a person breathes, air comes in through the nose or mouth and then goes into the trachea (windpipe). From there, it passes through the bronchial tubes, which are in the lungs. These tubes let air in and out of your lungs, so you can breathe. The bronchial tubes are sometimes referred to as bronchi or airways.