Longitudinal section of trachea (human, adult)

Stain: Azan. On top: the epithelium (1) is pseudostratified with cilia and goblet cells on a distinct basement membrane (↓). There is almost no demarcation (at this magnification) between lamina propria and submucosa due to the dense blue (2) staining of elastic fibers reinforced by collagen fibers. Mixed seromucous tracheal glands (3) and fat cells (4, white) are localized in the submucosa, in between a red-stained blood vessel (*). The perichondrial edges of hyaline cartilage (6) are connected by a fibrous tissue (5, fibroelastic membrane).