Nasal lining. Coloured scanning electron micrograph (SEM) of folded stratified squamous epithelium from the lining of the nasal cavity. The nasal cavity warms, humidifies and filters inspired air. The lining contains moisture- secreting cells, mucus-secreting cells and sensory cells. Mucus traps foreign particles such as bacteria and dust, preventing them from entering the lungs. The folds increase the surface area of the lining, allowing more secretory and sensory cells. Magnification: x150 when printed 10 centimetres wide.