Cilia and flagella

Cilia and flagella are highly motile structures containing microtubules and dynein (- end directed motor) as their key constituents. Cilia and flagella can be distinguished by their beating patterns but are nearly identical in structure. Flagella tend to be longer than cilia. Both cilia and flagella can propel cells as they cycle rapidly beating up to 100 t/s. Co-ordinated beating of many cilia can move large cells. Alternatively, if the cells are immobilised, like epithelial cells lining an animal respiratory tract, co-ordinated beating of cilia propels liquid and particles over their apical surfaces.