Ciliary Movement

The rhythmic, sweeping motion of epithelial cell cilia, ciliate protozoa, or flagella, caused by the alternating contraction and relaxation of contractile threads (myoids) on one side of the cilium or flagellum.

Although the mechanism of ciliary movement has been thoroughly investigated from a morphological standpoint, there is no good understanding of the functions of the various components of the process. The gills of Mytilus edulis were employed in this investigation, as previously described (Orton, 27). It is completely owing to the movement of the cilia that an effective stream of water is maintained on the gill face and that food is transported up to the animal’s mouth. The presence of these currents may be easily recognised with the naked eye using carmine particles. Cilia often beat or move in unison, whereas flagella beat separately.

Cilia are classified into two types:

1.Stereocilia, which are stationary cytoplasmic extensions, such as the epididymis’s cilia, and the macula and crista of the internal ear. Stereocilia lack microtubules. They include around 3000 actin filaments that are arranged longitudinally.

2. Kinocilia: These are the cilia that move.

The ciliary apparatus is composed of two main components:

(1) The cilium, which is the thin cylindrical process that extends from the cell’s surface; 

(2) The basal body is the structure from which the cilium develops.

A third component exists in certain cells in the form of small fibrils or ciliary rootlets that originate from the basal body and converge into a conical bundle around the nucleus.

Variations in cilia structure:

There are nine peripheral fibrils in Tetrahymena cilia that are joined together as circlets but lack the two central fibrils and the asymmetric arms of subfibril A. (Gibbons, 1963, 1967). Afzelius (1963 a) and others have discovered cilia or flagella that do not follow the 9+2 pattern on occasion.

The detected aberrations include the following: I forms that lack two central fibrils; (ii) forms that have more than two central fibrils; (iii) forms that lack peripheral fibrils; and (iv) forms that contain supernumerary peripheral fibrils. Typically, nonmotile cilia lack the two central fibrils.

Chemical composition of Cilia:

Cilia and flagella are both constituted of 70–84 percent proteins, 13–23% lipids, 1–6% carbohydrates, and 0.2–0.4% adenine and uracil nucleotides. The core fibrils and the arms of the peripheral fibril’s subfebrilA include the protein dynein, which contains the enzyme ATPase. The peripheral fibrils include a protein that is very similar to the actin protein found in muscle cells.

Movements of cilia:

Cilia have two distinct types of motions (rhythms):

(1) Metachronic rhythm, in which cilia in a single row beat sequentially; and (2) Synchronic rhythm, in which cilia in a single row beat sequentially.

(2) Isochmnic or synchronous rhythm, in which all the cilia in a row beat at the same time.

Unlike cilia, flagella exhibit undulant movement, with contraction waves propagating from the attachment site to the border. The flagella beat autonomously.

Origin of cilia:

Cilia is derived from centrioles. It is possible that basal bodies synthesise ciliary proteins independently of centriolar RNA and DNA components. Condensation of vacuoles within specialised mitochondria results in the formation of new basal bodies (Ehret and De Haller, 1963). Centrioles may be involved in the regulation of the synthesis and aggregation of the monomers of proteins essential for the creation of these tubular structures.

Conclusion

Cilia are essentially hair-like protrusions that arise from the plasma membrane. Cilia are involved in movement and mechanoreception. Ciliated organisms are those that possess cilia. The cilia on their tongues are employed for eating and movement.

Cilia is made up of dynein, a motor protein, and microtubules. Tubulin is a linear polymer of globular proteins. Ciliary movement is defined as the rhythmic movement of cilia that results in fluid or cell movement. Cilia are a kind of bacterium found in eukaryotic cells.