Mucosa of trachea

The mucosa (mucous membrane) is continuous above with that of the larynx, and below with that of the bronchi. It consists of areolar and lymphoid tissue, and presents a well-marked basement membrane, supporting a stratified epithelium, the surface layer of which is columnar and ciliated, while the deeper layers are composed of oval or rounded cells. Beneath the basement membrane there is a distinct layer of longitudinal elastic fibers with a small amount of intervening areolar tissue. The submucous layer is composed of a loose mesh-work of connective tissue, containing large bloodvessels, nerves, and mucous glands; the ducts of the latter pierce the overlying layers and open on the surface.