Question

Acrosome reaction of the sperm occurs due to:

• A. It's contact with zona pellucida of the ova
• B. Reactions within the uterine environment of the female
• C. Reactions within the epididymal environment of the male
• D. Androgens produced in the uterus

Answer 1

The correct option is A It's contact with zona pellucida of the ova

One of the three glycoproteins, ZP3 present in the zona pellucida functions as a sperm receptor and binds to a complementary molecule on the surface of the sperm head. Binding of the sperm head to the receptor molecule (ZP3) induces the acrosome of the sperm to release it's hydrolytic enzymes (sperm lysins).

The sperm lysins include:
(i) Hyaluronidase, that hydrolyses hyaluronic acid of the follicular cells.
(ii) Corona penetrating enzyme dissolves corona radiata portion around the secondary oocyte by hydrolysing their ground substances.
(iii) Acrosin helps to digest zona pellucida.

All these enzymes dissolve the corona radiata and zona pellucida sorrounding the egg and enable the sperm to reach the plasma membrane of the egg. The above changes in the sperm is called acrosome reaction.