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1. any of the short thread-like projections on the surface of a cell, organism, etc., whose rhythmic beating causes movement of the organism or of the surrounding fluid
2. the technical name for eyelash
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a slender filamentous or setaceous process found on cells that is capable of rhythmic movements. Among Protozoa, cilia are characteristic of infusorians. In some lower multicellular animals, such as turbellarians, cilia are found on all external covering elements (integumentary epithelium). The larvae of most coelenterates and sponges have a ciliated covering. In vertebrates, including humans, only a few specialized cells have cilia. For example, in man cilia cover the epithelium of the respiratory tract, the eustachian tubes, the vasa deferentia, the oviducts, and the uterus. Locomotor activity of the cilia ensures movement of the cell in a fluid medium; a ciliated cell that is fixed to a substrate produces currents of fluid in the surrounding medium.

The average cilium has a length of 5–15 microns and a diameter of 0.1–0.6 microns. The number of cilia on one cell ranges from ten to 22 in man to 2,500–15,000 in infusorians. The ultra-structures of cilia and flagella are identical. Externally cilia are covered with a three-layered membrane that becomes the surface membrane of the cell. In the center are two central tubular fibrils, which extend the length of the cilia, and nine peripheral fibrils, each of which is double. In the superficial layers of the cell cytoplasm, each cilium originates from the basal body, which has a structure similar to that of the cilium but lacks the central fibrils. The peripheral fibrils cause movement of the cilium, and the central ones apparently play a supportive role and possibly serve to conduct excitation.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
At least some captures are by direct interception, in which a prototrochal cilium overtakes a particle and adheres to it (Romero et al., 2010).
Cilium is considered to be a relatively inert IOFB and shown to be tolerated for 50 years (one case report).
Briefly, the process of PC assembly begins with the formation of the basal body, the mother centriole from which the cilium nucleates, and its migration and docking to the actin-rich cortex located at the cell surface.
Mimura et al., reported an asymptomatic subconjunctival cilium without hyperemia or edema.
The findings, made in mice, suggest that it might be possible to modify obesity through interventions that alter the function of the cilium, according to scientists at Columbia University Medical Center (CUMC).
than one primary cilium. Doubling or tripling the number of cilia on a cell meant that messages sent by an important development protein called sonic hedgehog were diluted by the time they reached their targets, the researchers reported in the Sept.
Unaccompanied and Pat Smullen draw clear of Cilium, with the disappointing St Nicholas Abbey (third right) behind
Given the fact that almost all proteins implicated in CDKs are at least partially localized in the renal cilium, its vital importance is emphasized and the notion that normal cilium structure and function are essential for renal development and maintenance is supported.
Considering the history of trauma in CASE S, we believe the cilium was mechanically embedded on the cornea at the time of injury and got buried as the surface reepithelialized.
So-called "primary cilia" have been attracting intense attention as recent research has confirmed their role in monitoring the cell's exterior environment and conveying information to the rest of the cell using an arsenal of signals stored inside the thin interior of each antenna-like cilium.
In captures, the overtaken particle then moved with the cilium until it was near the food groove.