Trachea epithelium. Light micrograph of a section through the wall of the human trachea (windpipe), showing cell layers. The epithelium (blue) is the surface layer: it is composed of ciliated cells with hair-like cilia seen projecting into the air space of the trachea; and goblet cells (white) that secrete mucous. Mucous traps dust particles and other air pollutants. While the cilia beat and so sweep foreign matter and mucous back up towards the larynx & out of the lungs. Connective tissue containing bands of fibro-elastic tissue, & sero- mucous glands are found below the epithelium. Magnification: x50 at 35mm size.