# Bronchi --- **Bronchi** are the hollow tube-shaped structures of the [[respiratory tracts|lower respiratory tract]] that are in the [[lungs]]. Air passes through them on it's way to the [[alveoli]] where oxygen from the air and carbon dioxide in the blood is exchanged. The bronchi are arranged in a highly branched hierarchy called the **bronchial tree**. ![[bronchi types.png]] - **Main bronchi** branch off the [[respiratory tracts|trachea]] - there is a left and a right main bronchi—one for each lung - **Lobar bronchi** branch off each main bronchi - there are two *left* lobar bronchi, and three *right* lobar bronchi—one for each [[lungs#Lobes|lobe]] in each lung - **Segmental bronchi** branch off each lobar bronchi - there is one that corresponds to each [[lungs#Bronchopulmonary Segments|bronchopulmonary segment]] - **Small bronchi** branch off many times from each segmental bronchi - typically there are 9-12 total "generations" of bronchi, and the main, lobar and segmental branches are only the first three - **Bronchioles** are what small bronchi become when reach a size of about 1 mm and lack cartilage in the walls and are thus able to [[#Bronchiodialation & Bronchoconstriction|constrict/dialate]]. - **Terminal bronchioles** are brionchioles that no longer branch off and terminate in an [[alveoli|alveolar sac]] ![[bronchi.png]] ## Bronchoconstriction & Bronchodilation **Bronchoconstriction** is a narrowing of the bronchioles due to a constriction of the [[smooth muscle]] that makes up the walls of the bronchioles. Causes [[lung sounds|wheezing]] and [[dyspnea|shortness of breath]]. **Bronchodilation** is the dilating of the bronchioles due to a relaxation of that smooth muscles. Caused by [[sympathetic nervous system|sympathetic]] stimulation. [[bronchodilators]] are beds that cause bronchodilation, often used for breathing problems. ## Problems with the Bronchi - **bronchitis** is an inflammation of the bronchi; there are two types, acute and chronic - **Acute bronchitis** develops rapidly as a result of a cold or other infection and is usually over in 10-14 days - [[COPD|chronic bronchitis]] is a form of COPD which results form long-term exposure to irritants which causes long-term thickening of the bronchial walls and the production of extra mucus. - [[asthma]] is an obstruction of the bronchi due to an inflammatory response/mucus ___