Thursday, December 28, 2006


The primary cilium is a slender protuberance on the surface of nearly every cell in the body. Cilia are functioning organelles know to be essential to normal development and health. Some cilia are rigid spikes that gather sensory information, while other cilia are flexible and whip-like, registering or directing flow in the surrounding fluid. Cilia and flagella both have an internal structure built upon microtubules, but the flagellum is longer and is more often a single organelle. Inside both cilia and flagella is a microtubule-based cytoskeleton termed the axoneme, which provides scaffolding for various protein complexes. 3D diagram - axoneme : 3D animation – inside flagellum : image - detail of cilia : tem - structure cilium : diagram - mechanism of ciliary motility : Geometric Clutch Model : animation - cilia & flagella

The motor protein dynein powers the sliding of the microtubules against one another — first on one side, then on the other. This dynein-powered sliding produces a whip-like motion employed to move fluid past or over the cell. During the course of evolution, cilia have been adapted to function as mechanoreceptors, chemoreceptors, and the outer segment of the rods in the vertebrate retina. Although called stereocilia, the hair-cell protrusions in the inner ear are actually modified villi. sem image - inner ear stereocilia

The microtubular axoneme also provides binding sites for molecular motor proteins, such as kinesin II, which assist in the transport of proteins up and down the microtubules. 3D diagram - axoneme The microtubule organizing center, also called a basal body, lies at the base of the cilium. tem - basal bodies. The basal body is created as the centriole (a microtubular structure essential to cell division) migrates to the surface. The transition zone between axoneme and basal body serves as a docking station for intraflagellar transport and motor proteins. During intraflagellar transport (IFT) materials needed to build the cilia are carried to the ciliary tip and spent materials are carried down to the ciliary body. The IFT particle, which is made up of at least 17 polypeptide subunits, may also carry signals collected by various receptors embedded in the ciliary membrane.

More: Cilia, Flagella, and Centrioles : Cilia and flagella :
HHMI Bulletin September 2005: The Importance of Being Cilia
Google cilia

Virtual Cell Textbook - Cell Biology : Main page of BioChemistry : Main page of Molecules : Main page of Pathways : Main page of Genes : Main page of Cell : Main page of Cell to Cell : Main page of Neuron: Main page of Brain:


Blogger dronbyfoto said...

I like it! Good job. Go on.

10:58 PM  

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