The bronchioles or bronchioli are the first airway branches that no longer contain cartilage. They're branches of the bronchi, and are smaller than one millimeter in diameter. There're no glands or cartilage in any of the bronchioles, and the epithelial cells become more cuboidal in shape. The bronchioles terminate by entering the circular sacs called alveoli. Control of airflow resistance and air distribution in the lungs's controlled by the bronchioles. Pathology Bronchospasm, a life-threaten… (More on Bronchiole)