Alveolar ducts are the result of ramification of the air passages at the end of the respiratory bronchioles. There are approximately 1.5-2 million per lung. Each duct is lined by Clara cells and the occasional epithelial cell; between these are the openings of multiple alveoli. At the distal end of the duct, there is a division into two or more alveolar sacs. There may be isolated areas of cuboidal epithelial cells and smooth myocytes within their walls.
The alveoli permit gaseous exchange to occur within the alveolar ducts.
Last reviewed 01/2018