Fig. 4.

Movement patterns of 9+2 motile cilia and 9+0 motile cilia. The 9+2 motile cilia are found in the lateral ventricle, respiratory ducts, female reproductive system, and sperm. 9+0 motile monocilia are located at the surface of the embryonic ventral node and rotate quickly to create a smooth leftward flow, which determines the left-right asymmetry of the animal body. The generation of the leftward nodal flow is dependent on the posterior tilt of the rotating cilia. Motile cilia beat coordinately along the anterior-posterior axis and generate a directional fluid flow, a phenomenon known as planar cell polarity. The sperm flagellum is a specialized 9+2 structure that gives sperm cells their motility.