bronchiole A small (less than 1 mm diameter) air-conducting tube of the tetrapod lung. Bronchioles arise as branches of a bronchus and terminate in alveoli. The walls of bronchioles are abundant in smooth muscle, which controls the size of the lumen. The cartilage and mucus glands found in bronchi are absent. Related category • ANATOMY AND PHYSIOLOGY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |