what is the function of bronchioles

Bronchioles are part of the tracheobronchial tree, which carries air to and from the lungs and exchanges gases such as oxygen and carbon dioxide. They are the smallest airways in the respiratory tract and lead directly to the alveolar ducts, which house the alveoli responsible for exchanging gases with the blood. The function of the bronchioles is to deliver air to a diffuse network of around 300 million alveoli in the lungs, where gas exchange occurs. Bronchioles are also supported by smooth muscle tissue, which surrounds each bronchiole and can constrict or dilate the airway, controlling airflow through contraction and dilation of the airway. The bronchioles are lined with cells that create mucus, which keeps the airways moist and traps bacteria, viruses, fungi, and other particles to protect the lungs and prevent infection. The bronchi are also lined with cilia, tiny hair-like structures that help move mucus and particles out of the lungs.