Changes

* When the spermatozoon completely penetrates the zona pellucida and reaches the perivitelline space, it settles into a bed of '''microvilli''' formed by the oocyte plasma membrane.

* When the spermatozoon completely penetrates the zona pellucida and reaches the perivitelline space, it settles into a bed of '''microvilli''' formed by the oocyte plasma membrane.

* Oocyte plasma membrane fuses with the '''equitorial segment''' and the fertilizing spermatozoon is engulfed.  

* Oocyte plasma membrane fuses with the '''equitorial segment''' and the fertilizing spermatozoon is engulfed.  

**Brought about by a fusion protein that is inactive prior to the [[Copulation_-Sperm_in_the_Female_Tract_- Anatomy & Physiology|acrosome reaction]].

**Brought about by a fusion protein that is inactive prior to the [[Sperm in the Female Tract - Anatomy & Physiology|acrosome reaction]].

* Nucleus of the spermatozoon is within the oocyte cytoplasm.

* Nucleus of the spermatozoon is within the oocyte cytoplasm.

* Sperm nuclear membrane disappears.

* Sperm nuclear membrane disappears.