trachea, pl. tracheae (tra´ke-a, -ke-e) [NA]
The air tube extending from the larynx into the thorax (level of the fifth or sixth thoracic vertebra) where it bifurcates into the right and left main bronchi. The t. is composed of from 16 to 20 rings of hyaline cartilage connected by a membrane (annular ligament); posteriorly, the rings are deficient for one-fifth to one-third of their circumference, the interval forming the membranous wall being closed by a fibrous membrane containing smooth muscular fibers. Internally, the mucosa is composed of a pseudostratified ciliated columnar epithelium with mucous goblet cells; numerous small mixed mucous and serous glands occur, the ducts of which open to the surface of the epithelium.windpipe; [G. tracheia arteria, rough artery]
saber-sheath t. a type of tracheal collapse seen in chronic obstructive pulmonary disease in which there is an increase in the outer posterior tracheal dimension with side-to-side narrowing involving the lower 2/3 of the trachea.
scabbard t. a deformity of the t. caused by flattening and approximation of the lateral walls, producing more or less pronounced stenosis.
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