cilium


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cilium

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

Cilium

 

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.

IU. I. POLIANSKII

References in periodicals archive ?
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).
The total arc of beat at the base of a prototrochal cilium exceeds 200[degrees] (Fig.
2+] influx through the cilium and into the renal epithelial cells.
Considering the history of trauma, the cilium was probably mechanically embedded on the cornea at the time of injury
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.
The lengths of prototrochal cilia or width of the food groove could possibly set an upper limit to size of particles captured and transported, but reported clearance rates over a range of particle sizes indicate that upper size limits on particles cleared from suspension are less than prototrochal cilium length or width of the food groove (Hansen, 1991, 1993; Riisgard et al.
Because there is only one cilium per cell (Strathmann, 1971), the stimulus must also be transmitted to neighboring cells.
When they sequenced the DNA in these ADPKD patient cells, the investigators found mutations in the gene that encodes polycystin-1, suggesting that polycystin-1 helps shepherd polycystin-2 to the cilium.
They found that these mutations lead to malfunctions in a protein called Tectonic1, one of several that forms a crucial collar around the base of a cilium.
The cilium is crucial as it is involved with cell signalling pathways during cell development in different parts of the body.