Abnormal Intraepithelial Glands in the Human Trachea

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Abstract
Among 25 tracheae studied systematically for intraepithelial glands we found in one patient –-a heavy smoker and former miner–-more than 5 000 intraepithelial mucous glands of a type which does not appear to have been reported previously. These glands were lying in clusters of 20–80, as solitary glands, in rows, or in festoons. The density of the glands within the clusters ranged from 65 to 250 glands/mm2. The number and density of the glands in the different parts of the trachea were fairly varied, the number being smallest in the membranous wall, largest in the lowest part of the cartilaginous wall. The architecture of the individual glands is described. It is composed of 30–50 mucous cells which are grouped especially at the bottom of a duct-shaped lumen which debouches on the surface of the trachea. The glands must be abnormal. It is endeavoured to explain the mechanism of their origin which is similar to the development of the normal submucous glands in the trachea. The formation of the intraepithelial glands may be a metaplasia of the epithelium due to a chronic irritant, possibly heavy smoking or long-lasting exposure to dust. The secretory capacity of the intraepithelial glands was calculated. It was small, amounting to 1/200–1/300 of the total secretory capacity of the goblet cells which was also increased in our patient.