Acrosome reaction

Acrosome reaction

The acrosome enzyme hyaluronidase and proteolytic enzymes released to open a pathway

for passage of sperm head through zona pellucida within 30 minutes, so fertilization will occur.

Why does only one sperm enter the oocyte?

1- Only few sperms get as far as the zona pellucida so that it might be 10, 20 or 30 minutes before the 2nd sperm arrives.

2- Within few minutes after the 1st sperm penetrate the zona pellucida, Ca++ diffuse through the oocyte membrane and cause release of cortical granules that prevent binding of additional sperms.

3- The oocyte membrane its fusion with sperm is believed to be electrically depolarized.