Cilia

Cilia: Populations of thin, motile processes found covering the surface of ciliates (Ciliophora) or the free surface of the cells making up ciliated Epithelium. Each cilium arises from a basic granule in the superficial layer of Cytoplasm. The movement of cilia propels ciliates through the liquid in which they live. The movement of cilia on a ciliated epithelium serves to propel a surface layer of mucus or fluid. (King & Stansfield, A Dictionary of Genetics, 4th ed)1

Anatomical Information about Cilia

Why are cilia important?

The human lung is exposed daily to inhaled pathogens, allergens, and irritants, and innate host defenses are crucial to prevent pulmonary injury and infection. Complex, local defenses have evolved to protect the airways, including the mucociliary escalator, which mechanically eliminates bacteria and particulates that deposit at the respiratory epithelium.

Cilia completely line the nasopharynx, middle ear, paranasal sinuses, and larger airways. Each ciliated cell has hundreds of cilia that are oriented and beat in the same direction. A normal cilium is a complex, specialized structure, composed of roughly 250 proteins. It contains an array of longitudinal axonemal microtubules, consisting of 9 doublets arranged in an outer circle around a central pair. Radial spokes radiate from the central pair to microtubule A and an incomplete tubule B. The principal protein of the microtubules is a - and b -tubulin. The microtubules are anchored by a basal body in the apical cytoplasm of the cell. Dynein, an ATPase and "motor" of the cilium, is attached to the microtubules and appears as distinct inner and outer dynein arms, and provides energy for microtubule sliding.

The shortening or absence of dynein arms (inner, outer, or both) is the most common form of the syndrome, occurring in ninety percent of cases with ultrastructural defects, but other structural abnormalities (like absent radial spokes) can produce decreased or absent ciliary movement.

Source: RDCRN (NCATS/NIH)2

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References

  1. Source: MeSH (U.S. National Library of Medicine)
  2. Source: RDCRN (NCATS/NIH): rarediseasesnetwork.org/ cms/ gdmcc/ Learn-More/ FAQs

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