[Concept of defects in the interrupted development of the bronchopulmonary system. I. Aplasias and hypoplasias].

The defects in case of interrupted development of broncho-pulmonary systems are intranatal, perinatal and postnatal deviations from its normal development. They could be: 1) aplasias; 2) hypoplasias; 3) dysplasias. The aplasias are early intranatal dysembryopathies, originating under the effect of epigenetic and paragenetic factors. In classical aplasias, the rudimentary development of a bronchus, first and second generation is the absence of pulmonary parenchyma, is concerned. In aplasias of the air passages of third, fourth, etc. generations, the primitive mesoderm could undergo cyst-like formation via independent differentiation to "primitive air spaces", with collagenous ventilation without direct bronchial communication. The hypoplasias are defects, associated with the abortive development both of air passages and the pulmonary parenchyma under the effect of paragenetic factors. They are manifested in four forms: 1) classical hypoplasias; 2) hypoplasias with cylindrically dilated bronchi; 3) hypoplasias with ampullarly dilated bronchi; 4) late hypoplasias. There are numerous intermediate forms among those basic forms, confirming their pathogenetic common origin and justifies their inclusion in the common group. The classical hypoplasias correspond to the description given by P. Schneider (1912). The hypoplasias with cylindrically dilated bronchi correspond to the so-called congenital cylindric bronchiectasis. The hypoplasias with ampullar dilations of bronchi correspond to the so-called congenital ampullar bronchiectasis. The late hypoplasias correspond to the so-called dysontogenetic bronchiectasis. In our opinion, the term hypoplasia, in pathologoanatomical and pathogenetic sense, is more informative and reflects the associated abortive development of the air passages and pulmonary parenchyma.