DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY
Nasopharynx surface, scanning electron micrograph (SEM). Seen here are: squamous nasal epithelial cells, a ciliated nasal epithelial cell and an M cell (lymphoepithelium). The nasopharynx lies behind the nose and above the level of the soft palate. Stratified squamous nasal epithelial cells line the surface of the nasopharynx (tightly packed together in this image). The epithelial cell surfaces are covered with microvilli that increase the cell surface area. Mucus, secreted by cells in the epithelial lining (not seen), traps foreign objects, preventing them from entering the lungs. Near the centre of the image is a ciliated nasal epithelial cell. Coordinated, beating of the cilia (hair-likr) propels the mucus to the back of the pharynx, where it is swallowed. The M-cell is part of the lymphoepithelium and aids in transporting foreign antigens to the underlying lymphoid follicles. Magnification: x1,200 when shortest axis printed at 25 millimetres.
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