Anatomy and Physiology Resource Site

10.6 - Fertilization

After copulation, the male and female haploid gametes must join in the process of fertilization in order for a new diploid zygote to be made.

Factors affecting the male and female gametes coming into contact:

The female reproductive tract is acidic and will kill sperm if they remain in the female reproductive tract for more than 1-2 days
The mature egg cell releases allurin to attract the sperm into the correct oviduct
Fertilization must occur in a small window of time (2-3 days) in the female reproductive cycle in order for implantation to be successful

If the sperm reaches the ovum at the appropriate time, the sperm still has several barriers to overcome before it can fertilize the ovum.

Sperm must "tunnel" through a loose layer of cells surrounding the ovum, the corona radiata
Acrosomal enzymes must digest the zona pellucida (a coating around the ovum) in a process called the acrosome reaction
Once a single sperm has fused with the ovum cell membrane, additional sperm are prevented from fusing with the ovum by the block to polyspermy, a chemical reaction inside the ovum

Within one hour after fertilization the sperm and ovum nuclei fuse to create the new diploid zygote.

Figure 10.6 - Layers of the female ovum.