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The cilium (pl.: cilia; from Latin cilium ' eyelid '; in Medieval Latin and in anatomy, cilium) is a short hair-like membrane protrusion from many types of eukaryotic cell. [1] [2] (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike projection that extends from the surface of the much larger cell body. [2]
Cilia movement in a metachronal wave. The coordinated movement of the cilia on all the cells is carried out in a fashion that is not clear. This produces wave-like motions that in the trachea, move at a speed of between 6 and 20 mm per minute. [2] The wave produced is a metachronal wave that moves the mucus. [5]
Cilia Structure. Primary cilia are found to be formed when a cell exits the cell cycle. [2] Cilia consist of four main compartments: the basal body at the base, the transition zone, the axenome which is an arrangement of nine doublet microtubules and considered to be the core of the cilium, and the ciliary membrane. [2]
Cilia performs powerful forward strokes with a stiffened flagellum followed by relatively slow recovery movement with a relaxed flagellum. In contrast to flagellates, propulsion of ciliates derives from the motion of a layer of densely-packed and collectively-moving cilia, which are short hair-like flagella covering their bodies.
[1] [2] Cilia and flagella are found on many cells, organisms, and microorganisms, to provide motility. The axoneme serves as the "skeleton" of these organelles, both giving support to the structure and, in some cases, the ability to bend. Though distinctions of function and length may be made between cilia and flagella, the internal structure ...
Plasmodium falciparum cilia and the sperm flagella of Drosophila are examples of cilia that assemble in the cytoplasm and do not require IFT. The process of IFT involves movement of large protein complexes called IFT particles or trains from the cell body to the ciliary tip and followed by their return to the cell body.
The cilia beat in one direction, moving mucus towards the throat where it is swallowed. Moving down the bronchioles, the cells get more cuboidal in shape but are still ciliated. Glands are abundant in the upper respiratory tract, but there are fewer lower down and they are absent starting at the bronchioles.
The body and oral kinetids make up the infraciliature, an organization unique to the ciliates and important in their classification, and include various fibrils and microtubules involved in coordinating the cilia. In some forms there are also body polykinetids, for instance, among the spirotrichs where they generally form bristles called cirri.