Cilia are minute, iiairlike processes on the surface of protozoans or of metazoan cells which by their motion accomplish locomotion or produce a current. Each cilium contains a peripheral circle of nine doublet microtubules arranged around two single microtubules. Each microtubule is composed of tubulin proteins.
Although the mechanism of ciliary movement is not completely understood- It is known that the microtubules behave as sliding filament that move past one another much like the sliding filaments of vertebrate skeletal muscle. The fluxes of Ca2+ across the membrane is not responsible for controlling the organized beating of cilia.