They cross the collar of the uterus pretty much within ten minutes.  It is for this reason that women are often advised to not get up directly after!...

They cross into the uterus at a speed of 2 to 3 millimeters per minute, then they arrive at the fertilisation point within about 2 hours.  The journey is a rough one and only about 100 to 200 of the 'chosen ones' will arrive at the the most strategic place.

The spermatozoa next fix themselves onto a membrane that surrounds the egg and alters the shape of the acrosome at the head in order to create a drive-piling effect to try to enter the egg.

Only one can get through!  Once one is successful, the champion spermatozoon loses it's tail and it's head increases in size.  This entrance creates an 'activation' in the egg and it too begins to enlarge.  The two come closer and merge.

An animation of this process can be found at http://www.stanford.edu/group/Urchin/fusion.htm .... but again, this is in sea urchins, so if anyone can help us here.....

A small zygote now exists.  This will then begin to divide to hopefully produce a baby in nine months time!

Introduction

1. The Feminine Cycle

2. The Man's Contribution

3. The Fertilisation

4. How A Girl Or Boy Is Created

5. Marking the Ovulation Time

6. Calculating The Due Date Of Birth

Annex.  Female Anatomy