HISTOPHYSIOLOGY OF THE TRACHEAL EPITHELIUM IN RATS IN POSTNATAL ONTOGENESIS

Using a complex methodology of in vivo monitoring of the motor activity of the ciliary apparatus in combination with histological and morphometric methods, the epithelial lining of the trachea 110 Wistar rats was studied from birth until old age (24 months). In newborn animals, tracheal epithelium was characterized by the minimal content of the ciliated cells (18%), the maximum frequency of the ciliary beat (FCB) -15 Hz and the lack of directional movement of mucus. Within the 1st month of life, the most intensive growth in the number of the ciliated cells and their morphometric parameters (the height of the cell, the length of the cilia) was marked together with the formation of the pseudostratified structure of the epithelium. By the end of this period morphologically identifiable goblet cells first appeared. The emergence of mucociliary transport (0.03 mm/s) was registered since Day 14 after birth. Tracheal epithelium reached structural and functional maturity by the 3rd month of postnatal development, at this time, the velocity of mucus movement (VMM) increased to 0.1 mm/s, FCB at the age of 6-12 months was equal to 11.3-11.7 Hz. In the aged (24 month old) animals FCB increased to 12.9 Hz, while the morphometric parameters of the ciliated cells, the proportion of goblet cells and VMM reached their maximum values. At the same time, the number of the basal (cambial) cells in the epithelial layer was reduced, while the number of dying cells was increased. The results of the study indicate a close relationship between processes of structural and functional differentiation of the ciliated epithelium of the respiratory tract ensuring the effective operation of mucociliary apparatus throughout the life.

trachea, pseudostratified ciliated epithelium, ciliary apparatus, locomotor activity, postnatal ontogenesis