Figure 1.

The structure of centrosomes and cilia/flagella. The centriole, also called the basal body, is a structural constituent of centrosomes, cilia and flagella. The canonical centriole has nine microtubule triplets and is approximately 0.5 μm long and 0.2 μm in diameter. Each centrosome is composed of a mother (or grandmother) and daughter centriole present in an orthogonal configuration and surrounded by a matrix of proteins called the pericentriolar material (PCM). The older centriole (mother) shows subdistal appendages, where microtubules are docked, and distal appendages, which are important for docking to the cell membrane. In many cells the centriole migrates and tethers to the cell membrane via its appendages and seeds the growth of cilia and flagella. The skeleton of cilia and flagella, called the axoneme, results from a continuation of the basal body structure and might be composed of nine microtubule doublets with dynein arms and a central microtubule pair, as it is for most motile cilia (a); or nine doublets with no dynein arms or central pair, as it is in the case of most immotile cilia (b). The distal part of the basal body is called the transition zone, where the outer tubule stops growing. Adapted with kind permission from Springer Science + Business Media: Cell Mol Life Sci Centrioles: active players or passengers during mitosis? 67 (2010). 2173–2194. Debec A, Sullivan W, and Bettencourt Dias M, Figure  1, Copyright © The Author(s) 2010.