The term cilia is Latin for "eyelashes." Common in single-cell organisms, these hair-like structure wave to move the cell around or to move something around the cell. Cilia also are present on most cells in the human body. Some tissues in the body, such as the Fallopian tubes in women and the trachea, also have a special type of cilia that help transport substances along the tissues' surfaces
In the body, cilia on the surface of tissues are responsible for protecting a person from germs in the lungs and for pushing an ovum through the Fallopian tube, among other tasks. These cilia are called motile cilia, and they are found in groups and beat in waves. Primary cilia, on the other hand, usually are found only one at a time on cells
The rhythm of waving cilia is controlled by centrioles, which are organelles located inside the cell wall. Mitochondria, other units inside the cell, provide adenosine triphosphate (ATP), a source of cellular energy, for the cilia. The ATP directs the chemical kinesin to bind to certain parts of the cilia that control their movement. Thus, the cilia are able to beat or essentially swim their way through viscous liquid. Similar to cilia, flagella are longer such hairs, usually found in ones or twos, such as the tail of a sperm. They share many characteristics with cilia
Primary ciliary dyskinesia (PCD), also known as immotile ciliary syndrome, is a rare, ciliopathic, autosomal recessive genetic disorder that causes a defect in the action of the cilia lining the respiratory tract (lower and upper, sinuses, Eustachian tube, middle ear) and fallopian tube, and also of the flagella of sperm in males
This disease is genetically inherited. Structures that make up the cilia including inner and/or outer dynein arms, central apparatus, radial spokes, etc. are missing or dysfunctional and thus the axoneme structure lacks the ability to move. Axonemes are the elongated structures that make up cilia and flagella. Additionally, there may be chemical defects that interfere with ciliary function in the presence of adequate structure. Whatever the underlying cause, dysfunction of the cilia begins during and impacts the embryologic phase of development

PCD is a genetically heterogeneous disorder affecting motile cilia[5] which are made up of approximately 250 proteins.[6] Around 90%[7] of individuals with PCD have ultrastructural defects affecting protein(s) in the outer and/or inner dynein arms which give cilia their motility, with roughly 38%[7] of these defects caused by mutations on two genes, DNAI1 and DNAH5, both of which code for proteins found in the ciliary outer dynein arm

electron microscope image of lung trachea epithelium. There are both ciliated and on-ciliated cells in this epitheliumcilium diagram

cilium diagram
Normal cilia (A) and cilia representative of Kartagener's syndrome (B)

The main consequence of impaired ciliary function is reduced or absent mucus clearance from the lungs, and susceptibility to chronic recurrent respiratory infections, including sinusitis, bronchitis, pneumonia, and otitis media. Progressive damage to the respiratory system is common, including progressive bronchiectasis beginning in early childhood, and sinus disease (sometimes becoming severe in adults

In males, immotility of sperm can lead to infertility, although conception remains possible through the use of in vitro fertilization and, as well as this, there have been reported cases where sperm were able to move.[2] Trials have also shown that there is a marked reduction in fertility in female sufferers of Kartagener's Syndrome due to dysfunction of the oviductal cilia.[3]
Mucous Clearance

Small amounts of mucous are normally produced in the bronchial tubes to trap soot, bacteria, and other small particles we all breathe in every day, and larger amounts of mucous are produced when the bronchial tubes are inflammed (for example, after smoke or polluted air exposure, or during a respiratory infection). The cells lining the bronchial tubes are covered by tiny, moving hairs called cilia, which beat in the direction of the mouth.

The beating of these cilia moves mucous up the bronchial tubes and windpipe up to the mouth, where the mucous is either swallowed or, occasionally, coughed out.

The passages of the nose, sinuses, and Eustachian tube (the tube connecting the middle ear with the inside of the throat) are lined by tissues which are very similar to the tissues of the bronchial tubes, and the cells lining these passages are also covered by cilia

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Sagittal CT image showing "tree in bud" appearance of mucous impaction in distal small airways related to primary ciliary dyskinesia

Cross section of a cilium from a subject with normal motile cilia (top) and a subject with immotile cilia (bottom)

Cilia are made up of even tinier tubes, called microtubules. All cilia contain 9 outer pairs of microtubules, and 2 central single tubules. From each outer pair of microtubules, a pair of dynein "arms" reach towards the next pair of microtubules. The dynein arms actually grab the adjacent pair of microtubules in a specific order, which causes the cilia to bend. Radial spokes extend from each outer pair of microtubules towards the inner central tubules. Nexin links also join each outer pair of microtubules with the adjacent outer pair. Radial spokes and nexin links help stabilize the cilia's structure
Types of Abnormal Cilia
Abnormalities of any of the parts of cilia can lead the cilia being unable to beat. Abnormalities of all the components of cilia have been seen in individuals with Immotile Cilia Syndrome, including absence of the inner or outer dynein arms (or both), absence of the central spokes, absence of the nexin links, and various abnormalities of the microtubules. Abnormalities involving the dynein arms are the commonest cause of Immotile Cilia Syndrome. As all of these abnormalities lead to failure of the cilia to move, all of these abnormalities lead to the same symptoms. In rare instances, cilia from individuals with Immotile Cilia Syndrome look normal using the electron microscope, but video-microscope images show that the cilia fail to beat (for unknown reasons), or do not beat in a coordinated, forwards-and-backwards way. The symptoms in these individuals are the same as in other people with Immotile Cilia Syndrome