[Airway epithelium and its reaction to harmful substances]

The trachea and large bronchi are lined with a pseudostratified columnar ciliated epithelium. The secretory elements are represented by goblet cells. In healthy subjects the majority of goblet cells are filled with mucus, only 3% of them discharge secretion. Above the epithelium a regular ciliary border is developed. Among kinocilia with the 9 + 2 inner pattern about 1% of altered cilia are discovered. Goblet cells are the first to react to the majority of noxious substances with the exception of some inert dusts. Their number increases and the mechanism of secretion is accelerated. Damage to the ciliated cells is reflected in an impairment of the ciliary border where the average number of cilia per micron 2 declines and the ratio of altered cilia increases. To compare the effect of various noxious substances a classification of the degree of airway epithelium alteration was proposed. According to the degree of the ciliary border impairment and the functional state of the secretory elements the injury of the epithelium was classified as serious, moderately serious and mild.