PHOTO INSOLITE REALITE / SCIENCE PHOTO LIBRARY PHOTO INSOLITE REALITE / SCIENCE PHOTO LIBRARY
False-colour scanning electron micrograph (SEM) of interior surface of a human bronchus, 1 of the larger elements of the bronchial tree that conducts air to the alveoli (air sacs of the lung), where gaseous exchange occurs. The bronchial epithelium is covered with cilia (feathery in appearance) and mucous-secreting cells (mucous secreted appears yellow), which filter the incoming air of dust particles (the cilia are fine projections, which beat constantly, directing dust particles back towards the trachea). The mucous secreted helps scrub the air of harmful gases such as ozone and sulphur dioxide. Magnification: X 1700 at 35mm size.
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