Cilia are roughly 10 _m long hair-like protrusions of the cell membrane. In the airways of higher organisms, their coordinated oscillatory beating movements causes directed motion of the mucosal fluid, cleaning the airways from adhering inhaled particles and harmful substances.
It is obvious that in order to achieve efficient directed transport, the ciliary motions must be, at least locally coordinated. Immotile cilia or lack of coordination are made responsible for different severe diseases, such as primary ciliary dyskinesia, therefore there is a demand for reliable diagnostic techniques. The key to every diagnosis is a sound knowledge of the healthy system. To achieve this goal, we focus on two complementary lines of action: