Cellular component - Cilium
The cilium is a cell surface projection found at the surface of a large proportion of eukaryotic cells. The two basic types of cilia, motile (alternatively named flagella) and non-motile, collectively perform a wide variety of functions broadly encompassing cell/fluid movement and sensory perception. Their most prominent structural component is the axoneme which consists of nine doublet microtubules, with all motile cilia - except those at the embryonic node - containing an additional central pair of microtubules. The axonemal microtubules of all cilia nucleate and extend from a basal body, a centriolar structure most often composed of a radial array of nine triplet microtubules. In most cells, basal bodies associate with cell membranes and cilia are assembled as 'extracellular' membrane-enclosed compartments.
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