[The morphology of bronchial clearance]

The secretion of bronchiolar and bronchial epithelium was investigated in human biopsy material by electron microscopy. The secretion of Clara cells in the bronchioli of the goblet cells of bronchial epithelium and the secretion of peribronchial glands produce the gel phase of mucus above the bronchial mucosa. This gel phase is transported on the periciliary sol phase through the cilia beat, which consists of intercellular fluid. Foam-like, regularly arranged surfactant structures are detectable in this sol phase. Due to its surface-active qualities this surfactant, which is formed in the pneumocytes II of the alveolar system, has an anti-adhesive effect on the border between the sol and gel phase of the mucus. Furthermore, it contributes to the stabilisation of the water content in the sol phase, which is of decisive importance for the ciliary mucus transport. The morphological results agree with the results from the physiological and biochemical investigations, indicating that the surfactant has an important function in bronchiolar and bronchial clearance.