[Differentiation of cells of the bronchial wall in the early period of embryonal development of the lungs].

Electron microscopical analysis of cellular elements of the developing lung has been performed during early stages of the prenatal development. The mesenchymal anlage of the organ is characterized with an essential cell polymorphism. The precursors of the smooth myocytes are formed on the 13th day of embryogenesis and they develop in a close contact with epithelial tubules. Synthesis and accumulation of contractile elements are determining signs of myoblasts differentiation. Already at first stages of differentiation they interact by means of specialized junctions of adhesive type and from clusters, situating on periphery of the epithelial tubules. Increase in amount of contractile filaments in cytoplasm of myoblasts is accompanied with formation of the basement membrane of these cells. Together with myoblasts in the mesenchyme, cells of fibroblastic differon at various levels of development are described.