Extrusion of second polar body from egg occurs

Extrusion of second polar body from egg occurs after the sperm’s entry but before amphimixis (the fusion of the male pronucleus and the female pronucleus). At the time of ovulation, the secondary oocyte is arrested at metaphase II. Only the fi rst polar body can be found in theperivitelline space at that time.
Entry of a sperm into the secondary oocyte triggers the completion of meiosis II, resulting in the formation of second polar ody and ovum. 

(1) The fi rst cleavage occurs about 24 hours after the formation of the zygote. The second polar body is extruded before the formation of the zygote.

(3) The second polar body is extruded before amphimixis (the fusion of the male pronucleus and the female
pronucleus). 

(4) Just before the entry of a sperm, the oocyte is arrested at metaphase II. Only the fi rst polar body can be found in the perivitelline space at that time.