Editing Lung (section)

====Bronchial airways====
In the bronchi there are incomplete [[Trachea#Structure|tracheal rings]] of [[cartilage]] and smaller plates of cartilage that keep them open.<ref name="GuytonHall">{{cite book|last1=Hall|first1=John|title=Guyton and Hall textbook of medical physiology|date=2011|publisher=Saunders/Elsevier|location=Philadelphia|isbn=978-1-4160-4574-8|edition=12th}}</ref>{{rp|472}} Bronchioles are too narrow to support cartilage and their walls are of [[smooth muscle]], and this is largely absent in the narrower [[respiratory bronchiole]]s which are mainly just of epithelium.<ref name="GuytonHall"/>{{rp|472}} The absence of cartilage in the terminal bronchioles gives them an alternative name of ''membranous bronchioles''.<ref name="Abbott">{{cite journal |last1=Abbott |first1=Gerald F. |last2=Rosado-de-Christenson |first2=Melissa L. |last3=Rossi |first3=Santiago E. |last4=Suster |first4=Saul |title=Imaging of Small Airways Disease |journal=Journal of Thoracic Imaging |volume=24 |issue=4 |pages=285–298 |doi=10.1097/RTI.0b013e3181c1ab83 |pmid=19935225 |date=November 2009|s2cid=10249069 |doi-access=free }}</ref>
[[File:Secondary-pulmonary-lobule-illustration.jpg|thumb|A lobule of the lung enclosed in septa and supplied by a terminal bronchiole that branches into the respiratory bronchioles. Each respiratory bronchiole supplies the alveoli held in each acinus accompanied by a pulmonary artery branch.]]