TRACHEA, or WINDPIPE, the tube extending from the larynx, or organ of the voice, and from the level of the fifth cervical vertebra to the third dorsal ver tebra, at which latter point the trachea bifurcates or divides into two main bron chi or divisions, one supplying each lung with air tubes. The average length of the trachea is 4% inches and its diam eter about three-fourths of an inch. the latter measurement being greater in males than in females. The trachea con sists of fibrous membranes united by elastic cartilaginous rings, rendering the tube flexible and patent. The cartilages are circular but imperfect rings, each being joined posteriorly by fibrous mem brane. They vary from 16 to 20 in num ber. The muscular fibres of the trachea are of longitudinal and transverse ar rangement. The trachea is lined with mucous membrane, the epithelium of which is ciliated. The trachea receives blood from the inferior thyroid arteries, and nerves from the pneumogastric and recurrent trunks, and also from the sym pathetic system. The right bronchus, or one of the main divisions of the trachea, is wider and shorter than the left. It enters the lung opposite the fourth dor sal vertebra. The left bronchus is smaller and more oblique than the right and enters the left lung at the level of the fifth dorsal vertebra.
Diseases and Injuries of the The trachea is liable to inflammation and its products, and frequently suffers from extension of disease from the larynx. Acute inflammation may occur as an idiopathic affection, or a symptom of other disease, as smallpox, measles, typhus, tuberculosis, croup, etc. The symptoms are pain in the windpipe from the top of the sternum, expectoration of mucus, sometimes in regular rings, and a peculiar brazen-like cough. When con fined to the larynx there is no hoarse ness. Chronic inflammation usually ac companies follicular pharyngo-laryngi tis, tuberculosis, and syphilis. Constric tion of the trachea may be produced by aneurismal or other tumors pressing ex ternally on the trachea; or the symptoms may be produced by pressure on the nervous trunk, or the inferior laryngeal fibers. Constriction may also depend on undue muscular contraction, the seat thereof being immediately above the bifurcation of the trachea. Foreign bodies occasionally pass through the larnyx into the trachea, and the accident is a formidable one, which not infre quently proves fatal.