Editing Cilium (section)

===Motile cilia===
[[File:Bronchiolar epithelium 4 - SEM.jpg|thumb|[[Trachea]]l respiratory epithelium showing cilia and much smaller [[microvilli]] on non-ciliated cells in [[Scanning electron microscope|scanning electron micrograph]].]]
[[Mammal]]s also have '''motile cilia''' or '''secondary cilia''' that are usually present on a cell's surface in large numbers (multiciliate), and beat in coordinated [[Metachronal rhythm|metachronal waves]].<ref name="Lewin2007">{{cite book|author=Benjamin Lewin|title=Cells|url=https://books.google.com/books?id=2VEGC8j9g9wC&pg=PA359|year=2007|publisher=Jones & Bartlett Learning|isbn=978-0-7637-3905-8|page=359}}</ref> Multiciliated cells are found [[respiratory epithelium|lining the respiratory tract]] where they function in [[mucociliary clearance]] sweeping mucus containing debris away from the [[lung]]s.<ref name="2012-Enuka">{{cite journal | vauthors = Enuka Y, Hanukoglu I, Edelheit O, Vaknine H, Hanukoglu A | title = Epithelial sodium channels (ENaC) are uniformly distributed on motile cilia in the oviduct and the respiratory airways | journal = Histochemistry and Cell Biology | volume = 137 | issue = 3 | pages = 339–53 | date = March 2012 | pmid = 22207244 | doi = 10.1007/s00418-011-0904-1 | s2cid = 15178940 }}</ref> Each cell in the respiratory epithelium has around 200 motile cilia.<ref name=Horani/>

In the [[reproductive tract]], [[smooth muscle]] contractions help the beating of the cilia in moving the [[egg cell]] from the ovary to the uterus.<ref name="2012-Enuka" /><ref name="Panelli"/>
In the [[ventricular system|ventricles of the brain]] ciliated [[ependymal cells]] circulate the [[cerebrospinal fluid]].

The functioning of motile cilia is strongly dependent on the maintenance of optimal levels of [[Periciliary liquid layer|periciliary fluid]] bathing the cilia. [[Epithelial sodium channel]]s (ENaCs) are specifically expressed along the entire length of cilia in the respiratory tract, and [[fallopian tube]] or ''[[oviduct]]'' that apparently serve as sensors to regulate the periciliary fluid.<ref name="2012-Enuka" /><ref name="2016-Hanukoglu" >{{cite journal | vauthors = Hanukoglu I, Hanukoglu A | title = Epithelial sodium channel (ENaC) family: Phylogeny, structure-function, tissue distribution, and associated inherited diseases | journal = Gene | volume = 579 | issue = 2 | pages = 95–132 | date = April 2016 | pmid = 26772908 | pmc = 4756657 | doi = 10.1016/j.gene.2015.12.061 }}</ref>

====Modified motile cilia====
Motile cilia without the central pair of singlets (9+0) are found in early embryonic development. They are present as nodal cilia on the nodal cells of the [[primitive node]]. Nodal cells are responsible for the [[left-right asymmetry]] in [[bilaterians|bilateral animals]].<ref name="Desgrange"/> While lacking the central apparatus there are [[dynein arm]]s present that allow the nodal cilia to move in a spinning  fashion. The movement creates a current flow of the extraembryonic fluid across the [[primitive node|nodal surface]] in a leftward direction that initiates the left-right asymmetry in the developing embryo.
<ref name="Horani"/><ref name="Larsen"/>

Motile, multiple, 9+0 cilia are found on the epithelial cells of the [[choroid plexus]]. Cilia also can change structure when introduced to hot temperatures and become sharp. They are present in large numbers on each cell and move relatively slowly, making them intermediate between motile and primary cilia. In addition to 9+0 cilia that are mobile, there are also solitary 9+2 cilia that stay immobile found in hair cells.<ref name=Takeda/>

====Nodal cilia====
[[File:Nodal cilia.jpg|thumb|[[Scanning electron micrograph]] of nodal cilia on a [[mouse]] embryo]]
'''Nodal cells''' have a single cilium called a monocilium. They are present in the very early [[Embryonic development|development of the embryo]] on the [[primitive node]]. There are two areas of the node with different types of '''nodal cilia'''. On the central node are motile cilia, and on the peripheral area of the node the nodal cilia are modified motile.<ref name="Larsen">{{cite book |last1=Schoenwolf |first1=Gary C. |title=Larsen's human embryology |date=2015 |location=Philadelphia, PA |isbn=9781455706846 |page=64 |edition=Fifth}}</ref>

The motile cilia on the central cells rotate to generate the leftward flow of extracellular fluid needed to initiate the left-right asymmetry.<ref name="Larsen"/>