A disease syndrome caused by abnormal sub-microscopic structure of cilia, which therefore do not function properly during embryonic life, childhood and adulthood. The consequences are situs inversus, in which the developing internal organs in the embryo rotate randomly (so that 50% of affected people have their heart on the right side of the chest and their liver on the left side of the abdomen), abnormal sinuses, a bad form of chronic bronchitis called bronchiectasis, because mucus is not cleared from lungs properly, and male infertility because the sperm tail (the flagellum) has the same sub-microscopic structure as the cilia and cannot propel the spermatozoon. Curiously, female fertility is often normal or adequate: it seems the cilia of the fallopian tube's fimbrial end still make useful contact with the cumulus mass at ovulation, stopping the egg from getting lost and giving the muscular contractions of the tube the chance to carry the egg down to the ampullary-isthmic junction. Also called Kartagener's syndrome, after the Swiss physician Manes Kartagener, who first described a triad of situs inversus, abnormal sinuses and bronchiectasis.

Tiny hair-like projections on the surface of some cells, which are thus called 'ciliated'. Coordinated beating of the cilia moves mucus and mucus-like substances (such as the cumulus mass) on the surface of ciliated cells in the direction of the cilial beat. An individual cilium has the same basic sub-microscopic structure as the tail (the flagellum) of a sperm cell (a spermatozoon). See also immotile cilia syndrome. Plural: cilia.