bild

Lung lining. Coloured scanning electron micrograph (SEM) of a section through epithelial cells of the terminal bronchus (lung airway). Some of the cells are covered in cilia, tiny microscopic hairs. Rhythmic movements of the cilia serve to move mucus and trapped particles away from the gas-exchanging parts of the lung, and towards the throat, where they can be expelled. Magnification: x10,000 when printed at 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/EYE OF SCIENCE/SCIENCE PHOTO LIBRARY)