[Respiratory portion of the lungs of intact BALB strain mice].

Four male mice (1-month-old) of BALB strain have been studied. Three types of cells participate in formation of cellular lining of the terminal branchioles: ciliated, Clara cells and villose cells which are included in the neuroepithelial bodies composition. Clara cells are numerous and they are similar in their ultrastructural organization, they contain a great number of polymorphous secretory granules, single mitochondria and a poorly developed endoplasmic reticulum. A comparatively large number of pores of Khone are revealed: there are 4-8 pores per one alveole, and one pore is situated on 197.4 mcm2 of the alveolar surface. Alveolocytes of the second type of make the main actively secreting cell population of the alveolar passages and alveoles. Simultaneously, at the state of secretion there are 76% of the cells. The secretion of alveolar surfactant is realized by means of merocrine exocytosis. Relative volumetric fraction of mitochondria in alveolocytes of the II type comprises 12% and that of "cytophospholiposomes" (osmiophilic laminar bodies)--11%.