Trachea. Light micrograph (LM) of a transverse section through the trachea.At the top are the columnar epithelial cells that line the trachea. They have hair-like cilia on their surface that beat to move mucous, and particles trapped in it, upwards out of the respiratory tract. The mucus produced by mucosa glands (purple, hollow) and secreted by goblet cells in the epithelium. Magnification: 150 when printed at 10 centimetres wide