LH begins the resumption of meiosis, but the penetration of the egg by a sperm is what causes the completion of that process. After the LH surge, the first meiotic division occurs, but this division does not reduce the number of chromosomes. This is an equal division in which forty-six chromosomes are still left within the egg nucleus. Actually, it is more complex than this, and 1 will explain it in detail in chapter 12.

The “first polar body” is a small, divided nucleus that is pinched off from the main body of the egg prior to ovulation, about thirty hours after the LH surge. The extrusion of the first polar body from the egg shows that the first meiotic division has occurred under the influence of LH, meaning that the egg is now prepared to undergo the all-important second meiotic division. Many college biology students get confused by these two stages of meiosis. In the first division, all the chromosomes partly divide but do not split completely. /n the second division, they actually complete the split. The egg is thus prepared during meiosis for the entrance of a sperm.