Electron microscopic studies of the lung of the salamander, Hynobius nebulosus: 1. A scanning and transmission electron microscopic observation.

Abstract

The ultrastructure of the lung in the adult salamander, Hynobius nebulosus, was studied by light microscopy, scanning and transmission electron microscopy.The lung consisted of a pair of single air sacs, which have many septa and low ridges containing blood vessels on the internal surface. The internal epithelial cells were classified into respiratory epithelial cells (REC), ciliated cells, and mucous cells including goblet cells. Usually, the two latter were located at the internal end of the septa and at some low ridges, while REC were situated on the remaining internal surface. Mucous cells contained numerous discoid mucous granules and were observed to be transformed into goblet cells as a result of the maturation of these granules. REC also had more or less discoid mucous granules in the apical cytoplasm, and some REC contained many mucous granules as did the mucous cells. Lamellar bodies appeared not only in REC, but also sometimes in the ciliated and mucous cells. These results strongly suggest that REC in Hynobius nebulosus may combine in one cell the feature of pneumocytes with that of mucous or goblet cells.