The termination of the second meiosis of the oocyte
At the moment of impregnation one encounters the following condition in the secondary oocyte, which was created shortly before ovulation:
The mitotic spindle, arrested in the metaphase of the second meiosis, becomes active again due to the impregnation. From the docking and impregnating spermatozoon a signal for a resumption and termination of the second oocyte meiosis is triggered. One speaks now of an impregnated oocyte.
In the two hours following impregnation the mitotic spindle pulls the chromatids, situated around the equator, apart so that in the oocyte only 1n1C remains. A new formation of the 2nd polar body takes up the other 1n1C. The remaining first polar body bound by a thin cytoplasma bridge receives the same signal and also divides.
In what follows the structures of the mitotic spindle dissolve. Mitotic spindles formed in the future will be formed from the centrosome introduced by the father.