How does a sperm pass through the zona pellucida around an egg?

To pass through the zona pellucida, a mammalian spermatozoon must first undergo capacitation while traveling through the female genital tract, which enables it to perform the acrosome reaction.1

Contrary to the process in some other animals where a chemical lysin dissolves the egg's protective layers, the pathway through the zona pellucida in mammals is primarily mechanical. As the sperm contacts the zona pellucida, it creates an oblique slit by oscillating its head near the point of attachment. This process is highly specific, as the zona pellucida acts as a barrier that ensures only sperm of the appropriate species can bind and penetrate the egg.12