Following insemination, viable spermatozoa that are retained in the female reproductive tract must: 1) transverse the cervix, 2) be transported through the uterus to the oviduct, 3) undergo capacitation, 4) bind to the oocyte, 5) undergo the acrosome reaction and 6) penetrate the zona pellucida and fuse with the oocyte plasma membrane.  After fusion with the plasma membrane, the fertilizing spermatozoon enters the oocyte cytoplasm and its nucleus decondenses.  The male pronucleus is formed.  This signifies successful fertilization.