Bronchiole

Bronchioles are conducting airways and have a diameter of 1 millimeter or less. The ciliated, pseudostratified columnar epithelium remains the same as in the previous airways. At this level, the bronchioles are no longer surrounded by cartilage and display a ring of smooth muscle. They also lack glands. What is the orientation of the smooth muscle fibers surrounding the terminal bronchioles? How does this influence the shape of the bronchial mucosa?