The electron micrograph at the left shows absent (or very short) ciliary dynein arms in a case of ciliary dyskinesis. Normally, short inner and outer dynein arms jut from the microtubule doublets of a cilium. In the center is a microtubule singlet pair. The dynein arms are necessary for proper ciliary movement, and decreased ciliary motion predisposes to recurrent infection with inflammation and bronchial destruction. Kartagener syndrome is one form of ciliary dyskinesis in which additional abnormalities, including situs inversus, are present.