centrioles

Centrioles organize the spindle apparatus on which the chromosomes move during mitosis. Cilia and flagella are organized from peripheral centrioles (basal bodies).

Centrioles consist of 9 sets of triplet microtubules, and centrioles are arranged in pairs perpendicular to each other (tem - 9 triplet pair). animation - spinning centriole pair : tour centriole : zoom in on centriole. Џ beautiful Flash 8 animation - Inner Life of the Cell, which shows a centriole pair with radiating microtubules, and Interpretation: Inner Life of the Cell Џ

Unlike cilia and flagella, which are organized from microtubule organizing centers (basal bodies) at the cell periphery, centrioles have no central doublet of microtubules. Centrioles replicate autonomously, beginning from centers that contain proteins needed for their formation (tubulin, etc.). Procentrioles form first, each erecting a single microtubule from which the triplet can form (diagram - centriole formation). After a single centriole is constructed, daughter centrioles grow out from the tubules at right angles. In a non-dividing cell, they move to the periphery to form the basal body for the cilium (tem - basal bodies). In a dividing cell, the second centriole moves to the daughter cell (in a dividing cell). Where spindles are essential for chromosomal separation during reproduction, cilia are essential for cellular differentiation during embryologic development.

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 (functioning as 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.

More: Cilia, Flagella, and Centrioles : Cilia and flagella : HHMI Bulletin September 2005: The Importance of Being Cilia : Google cilia : Virtual Cell Textbook - Cell Biology :