Longitudinal section of trachea (human, adult)

Stain: Azan. On top: the epithelium (1) is pseudostratified with cilia and goblet cells. The dense lamina propria (2, ↓, deep blue) is demarcated from the submucosa with seromucous tracheal glands (3). C-shaped cartilage rings (C, light blue) maintain patency. The cartilage edges are connected by a fibrous tissue (5, fibroelastic membrane) and bands of smooth muscle fibers (contributing to the tunica fibro-musculo-cartilaginea). External to the latter an adventitia layer is present.