what is the function of bronchus

The bronchi are an essential part of the respiratory system, and their function is to carry air to and from the lungs. They also help moisturize the air you breathe and screen out foreign particles. The bronchi are lined with cells that create mucus, which keeps your airways moist and traps bacteria, viruses, fungi, and other particles to protect your lungs and prevent infection. The bronchi are also lined with tiny hair-like structures called cilia, which help move mucus and particles out of your lungs. The bronchi distribute the air throughout the lungs until reaching the respiratory bronchioles and alveolar sacs, which are the location for carbon dioxide and oxygen gas exchange across the wall of pulmonary capillaries and lung alveoli. The bronchi also contain smooth muscle between the mucosa and the fibrocartilaginous layers, which controls bronchi diameter and length and functions in the expiration of air from the lungs.