Animalia 6 Animals 6 animal tissue article 6 controlled study 6 female lung parenchyma 6 nonhuman 6 Amphibia 4 Amphibian 4 Anura 4 Bufonidae 4 Electronic microscopic 4 Lung 4 Lung ultrastructure 4 Melanophryniscus stelzneri 4 Microscopy, Electron 4 Microscopy, Electron, Scanning 4 Respiratory epithelium 4 Toad 4 Vertebrata 4 cell ultrastructure 4 comparative anatomy 4 lung alveolus cell type 1 4 lung alveolus cell type 2 4 lung structure 4 male 4 melanophryniscus stelzneri stelzneri 4 respiratory epithelium 4 scanning electron microscopy 4