The spindle fibers are used to control the movement and segregation of chromosomes in both the mitosis cell division and meiosis cell division. The spindles are referred to as the spindle apparatus and also mitotic spindle during mitosis or the meiotic spindle during meiosis. In both cases, the spindles serve the same purpose, which is to separate the daughter cells and their chromosomes.
Spindles are made up of microtubules and proteins. They extend from areas on the sides of the cell called centrioles on each end of the cell or at each pole. The spindles attach to the and attach directly to the chromosomes. Once the spindles are attached they do not simply pull the chromosomes apart, they first align them, and then proceed to separate them. The spindles do not grow without a type of balance in place.
The system that monitors the spindles and makes sure that the process of anaphase happens at the correct time is the kinetochores. The spindles are not completely round like the name might imply. Under a microscope, cross sections show that the spindles are somewhat ellipsoid in its shape. It also tapers from one end to the other of the structure. Not only is the process of the spindles grown monitored, it is protected on the growing end by plus-end microtubule proteins.