The submucosa is a loose connective tissue layer with lymphocytic infiltration as well as with large numbers of glands. The ducts from these glands deliver the mucous and serous secretions to the luminal surface of the trachea. Review the EM structure of cilia. The structure of the extrapulmonary bronchi is similar to that of the trachea. In the intrapulmonary bronchi , the respiratory epithelium and lamina propria are similar to those of the trachea, but the submucosal layer now contains smooth muscle fibers.
Several glands are still present.
The supporting cartilages become irregular plates held together by dense connective tissue. The intrapulmonary bronchi travel in large connective tissue septa. Smaller branches leave these septa and become surrounded with respiratory tissues. These are the ordinary bronchioles . These ordinary bronchioles with respiratory epithelia have no cartilage support in their walls and there are no glands.