[Receptor apparatus of the bronchioles and pulmonary alveoli].

Applying the method of silver impregnation in modification by Bielschowsky--Gros and Lavrentiev, two main types of sensitive neural terminals have been revealed in alveolar parenchyma: 1) sensitive neural terminals of bushy type, situating in the connective tissue of the alveolar walls, immediately under flat epithelium covering them; 2) sensitive neural apparatuses with a complex structure, protruding into the alveolar lumen. They are seen as an accumulation of epithelial cells, among them fine branches of myelin neural fibres (neuroepithelial bodies) terminate. Owing to space arrangement of the terminal branchings in the first type terminals, it is possible to consider them as mechanoreceptors accepting impulses which are connected with certain shifts in the pulmonary parenchyma during the process of respiration. Peculiar structure of the second type sensitive apparatuses (neuroepithelial bodies) and their arrangement in the pulmonary alveolar lumen suggest their connection with changes in the alveolar air composition. They are considered to be airreceptors.