Bronchiole

The bronchioles are the last part of the conducting system of the respiratory tract. They are branches of the small bronchi, and are smaller than one millimetre in diameter.

There are no glands or cartilage in any of the bronchioles, and the epithelial cells become more cuboidal in shape.

Bronchioles divide until they become terminal bronchioles, after these the respiratory bronchioles have sporadic alveoli on their walls. Eventually the respiratory tract branches into alveolar ducts, then alveolar sacs.