Fig. 6.

Transmission electron microscopic observation of cells lining the alveolus-like organoid from E13.5 tip epithelium cultured with FGF7 for 14 days. The alveolus-like structure is composed of squamous and cuboidal epithelial cells. L: lumen of the alveolus-like organoid. M: subepithelial matrix. a A squamous epithelial cell with thin cytoplasm is not well developed with organelles, and appears to be alveolar-type 1 cell. Bar = 5 µm. b A cuboidal cell has many lamellar inclusion bodies (arrows) and is considered as an alveolar-type 2 cell. Bar = 10 µm