Fig. 1
From: The pathology of small airways disease in COPD: historical aspects and future directions
Transitioning epithelial structure in a respiratory bronchiole. a A bronchiole demonstrating transition from the columnar epithelium to cuboidal epithelium and finally to flattened alveolar epithelium (2X magnification). b An enlarged image of the inset from image A showing columnar epithelium (black arrow), cuboidal epithelium (green arrow) and flattened epithelium (red arrow) (10X magnification). Section stained with hematoxylin and eosin