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Short, eyelashlike filament that is numerous on tissue cells of most animals. Capable of beating in unison, cilia perform a variety of functions, including providing the means of locomotion for some protozoans, moving mammalian ova (eggs) through oviducts, generating water currents to carry food and oxygen past the gills of clams, and cleaning debris from mammalian respiratory systems. Like a flagellum, a cilium has a central core consisting of two central microtubules surrounded by an outer ring of nine double fibres. Ciliary outgrowth is controlled by the basal body, located just inside the cell surface at the base of the cilium. Beneath the surface of some cells is a network of microtubular bundles that may coordinate ciliary beating.
This entry comes from Encyclopædia Britannica Concise. For the full entry on cilium, visit Britannica.com.