Bronchiole lining. Coloured scanning electron micrograph (SEM) of a section through the wall of a lung bronchiole showing the ciliated epithelial cells and their nuclei (yellow). Bronchioles link the larynx and bronchi to the lungs. The epithelial lining consists of mucus-secreting glands (not shown) and cells covered in cilia (green)(hair-like). Mucus ( grey) traps debris, such as dust particles or bacteria, in the inhaled air, while the beating of the cilia moves the mucus and particles upwards out of the respiratory tract. This helps to keep the lungs and airways clear and prevent infection. Magnification: x6000 when printed at 10 centimetres wide.