MITOTIC SPINDLE FIBERS
Fibers of mitotic spindle (cleavage spindle) appear as bunches of microtubules, which consist of tubuline and other proteins. Spindle structure is formed of two types of microtubules: the ones, which connect two poles of the spindle (polar microtubules), and the ones, which attach the poles of the spindle to kinetochores of chromosomes (kinetochore microtubules). Kinetochore fibers interact with polar fibers.