Cilia
There are two types of cilia; motile and primary, and they tend to be around 10um in length and around 0.2um in diameter[1]. Motile cilia grow in clusters e.g. the cells in the bronchial epithelium, primary cilia grow as a single cilium e.g. those on the embryonic node. Motile cilia are found on a limited range of different cell types whereas primary cilia are found on nearly every cell in the human body. Primary cilia's function is to recieve signals from other cells or fluids.
Motile Cilia
Cilia (singular: Cilium) are cylindrical organelles[2][3], built from microtubules, in a “9 + 2” arrangement[4], with 9 doublet microtubules surrounding the circumference and a central pair in the middle. The microtubules are regularly cross-linked with accessory proteins to make up the axoneme, a central core that provides stability. Certain accessory proteins such as dynein (see Figure 1) play a key role in the organelles movement. The 9 doublet microtubules around the circumference consist of one complete and one incomplete tubule, which are shared by common tubule wall. The organelle is also anchored to the cell membrane by the basal body, which is composed of triplet microtubules that transition into the doublet ones seen in the axoneme[5]. The majority of cilia in different eukaryotes have this characteristic arrangement[6]. They are motile structures whereby the rhythmic beating of cilia creates movement. Cilia are involved in mucociliary clearance in which bacteria, mucus and dust are swept up the respiratory tract into the mouth and eliminated by swallowing. Moreover, ciliated cells move oocytes along the fallopian tubes, and sperm from testes into the male reproductive tract[7]. Furthermore, by the beating of cilia, single cells are able to propel through fluid[8]. The movement of cilia is caused by axoneme, which can reach a length of 10-200 micrometers[9]. Dynein is a cytoskeleton motor protein within cilia which enables them to have movement. This occurs by the conversion of chemical energy in ATP to mechanical energy.[10]
Primary Cilia
Cilia can also be immotile (primary cilia) and have a “9+0” arrangement where they have 9 peripheral doublet microtubules and 0 single microtubules in the centre[11][12].
References
- ↑ The Histology Guide - The University of Leeds. Epithelia: Specialisations; Available from: http://www.histology.leeds.ac.uk/tissue_types/epithelia/epi_specialisations.php
- ↑ 5) “Fundamental role of microvilli in the main functions of differentiated cells: Outline of an universal regulating and signalling system at the cell periphery” K. Lange, J Cell Physiol. 2011, 226, 896-927 Abstract. https://www.ncbi.nlm.nih.gov/pubmed/20607764
- ↑ Lynn H. (2008) The Ciliated Protozoa Characterization, Classification, and Guide to the Literature, New York: Springer
- ↑ Lynn H. (2008) The Ciliated Protozoa Characterization, Classification, and Guide to the Literature, New York: Springer
- ↑ Jeff Hardin, Gregory Bertoni, Lewis J. Kliensmith, Becker's World of the Cell, Page 453, Eighth Edition, Benjamin Cummings, Pearson, San Francisco, 2010
- ↑ Alberts B, Johnson A, Lewis J, Morgan D, Raff M, Roberts K, Walter P. Molecular Biology of the Cell. 6th Ed, New York; Garland Science. 2015 (page 941-942)
- ↑ Martini FH, Nath JL, Bartholomew EF. Fundamentals of Anatomy and Physiology. 9th Ed, San Francisco; Pearson Education Inc: 2012 (page 70-71)
- ↑ Alberts, Bruce et al. (2008). Molecular Biology of the Cell, 5th edition, New York: Garland Science. (Page 1031)
- ↑ Alberts B, Johnson A, Lewis J, Morgan D, Raff M, Roberts K, Walter P. Molecular Biology of the Cell. 6th Ed, New York; Garland Science 2015 (page 941-942)
- ↑ https://www.ncbi.nlm.nih.gov/pubmed/20607764
- ↑ Satir P, Pedersen LB, Christensen ST. The primary cilium at a glance. Journal of Cell Science 2010; 123(499-503): 1. http://jcs.biologists.org/content/123/4/499 (accessed 14 November 2016).
- ↑ 5) “Fundamental role of microvilli in the main functions of differentiated cells: Outline of an universal regulating and signalling system at the cell periphery” K. Lange, J Cell Physiol. 2011, 226, 896-927 Abstract. https://www.ncbi.nlm.nih.gov/pubmed/20607764