Figure 1. Diagram of a transverse section of a cilium or a flagellum. The major elements of the internal axoneme are nine peripheral microtubule doublets surrounding a central pair of single microtubules. Pairs of dynein arms attached to one doublet interact with the adjacent doublet to produce relative sliding. This is then converted into ciliary or flagellar bending by other structures including nexin links and radial spokes.

Figure 2. Diagram of a vertebrate nerve cell showing the extended axon and a number of short dendrites. The polarity of the axonal microtubules is shown, and the bidirectional anterograde (outward) and retrograde (backward) transport along the axon is indicated.

Figure 3. Diagram showing the shape of a migrating fibroblast (a) from above and (b) in profile. The leading edge of the cell is thought to extend as a result of the formation of actin filaments in the broad flattened lamellipodium and numerous fine filopodia.