Fibrous, hollow rods consisting of thousands of sub-units made of the protein tubulin. As a tubular structure, they are 25 nm in diameter, a length varying from 200 nm to 20 micrometers, with a wall thickness of 5 nm. Found in eukaryotic cells, and throughout the cytoplasm, they are an essential component of the cytoskeleton that help in supporting the shape of cells, and in forming the internal structure of cilia and flagella. They serve other important cellular functions as well. Exhibiting dynamic behavior, they provide platforms (or routes) for intracellular transport such as the movement of organelles. In fact, they are part of a small pair of organelles called centrioles that enable cells to divide. Involved in mitosis (and meiosis), they promote the formation of mitotic spindles, which in turn enables the process by which eukaryotic cells separate their chromatids (i.e., they separate chromosomes during mitosis). During embryogenesis, they are crucial to the process of morphogenesis (i.e., in the formation of the architecture of the body) and to the formation of the brain morphogenesis through the activity of microtubule-associated proteins (MAPs).
See Acrosome, Axon hillock, Centrioles, Chromatid, Chromosome, Cilia, Cytoplasm, Cytoskeleton, Embyrogenesis, Eukaryote cell (or organism), Flagella, Growth cone, Meiosis (or reduction division), Mitosis, Morphogenesis, Organelles, Proteins