ASTRID & HANNS-FRIEDER MICHLER / SCIENCE PHOTO LIBRARY ASTRID & HANNS-FRIEDER MICHLER / SCIENCE PHOTO LIBRARY
Light micrograph of the human trachea (windpipe). The epithelium (layer on left, forming the lining of the lumen) is composed of two types of cell; ciliated cells with long, grass-like projections and mucus-secreting goblet cells, which are covered in short microvilli. The mucus secreted by the goblet cells to trap large dust particles and also scrubs inhaled air of gaseous pollutants such as ozone & sulphur dioxide. A rhythmic beating of the cilia also acts as a filter to particles suspended in the incoming air, sweeping dust & other foreign material back towards the larynx. Magnification: x20 at 35mm size.
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