Microtubules are cytoskeleton components that are made of two proteins, α-tubulin and ß-tubulin. They originate from centrosomes and serve three functions. First, they form the mitotic spindle of mitosis. Second, they make up cilia and flagella. Third, In nerve cells, they form a “railroad track” that motor proteins like kinesin and dynein travel on. Microtubules are also dynamic; they frequently lengthen and shorten.