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 ?
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).
2+] influx through the cilium and into the renal epithelial cells.
Furthermore, the possible implication of the cilium in planar cell polarity has also been addressed.
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.
A cilium forms like a short drinking straw being pushed outwards from inside an inflated balloon.
In ciliopathies such as Bardet-Biedl Syndrome, the primary cilium of cells is abnormal and leads to a host of problems.
During the study, the researchers observed that the enzyme goes to a cellular structure known as the cilium, a long-forgotten organelle without clear function until recently.
However, in the past five years, the field of cilia biology has exploded due to the recognition that many of our basic bodily functions are regulated and "fine-tuned" by the cilium.
The cilium is the technical name for which part of the face?