Fig. 2.

The normal airway epithelium lining the tracheobronchial tree contains more cell types. The main cell types in the upper part of the tree are represented by ciliated cells, goblet cells and basal cells, in lower branches these types are gradually replaced by club cells. Among main cells the minor cell types are irregularly interspersed. Hypoxia influences both cellular proliferation and cilia formation. The proliferation was observed mainly in the population of secreting cells - goblet cells and club cells. Cilia of ciliated cells under hypoxic conditions become shorter and sparse.