Why Do Polar Bodies Form?

A polar body forms as a result of the asymmetric division of an immature egg cell, also called an oocyte, according to Biology Online. Polar bodies always occur during the process of cell division as a vital part of meiosis and mitosis.

In the early stage of cell division, meiosis, the division of the immature egg cell or oocyte results in cells that are not evenly divided. One of these cells is much smaller than the other. The larger cell is the secondary oocyte while the smaller cell is the primary polar body. This primary polar body is generally released right before ovulation.

During the next stage, mitosis, the secondary oocyte divides. This occurs when the egg cell has left the ovary and has made contact with a sperm cell. However, polar bodies cannot be fertilized. The two cells that result after this second division are a mature egg cell and one additional polar body. The primary polar body from the first division undergoes its own mitosis, producing two secondary polar bodies. Most of these polar bodies, which were more or less used as filler during the meiosis and mitosis process, do not have any use at this point and die shortly after.