State the role of the zona pellucida after a sperm has fused with the ovum.
Answer
It undergoes the cortical reaction to become a zona reaction layer that blocks entry of additional sperms (prevents polyspermy).
Step-by-step solution
- Identify that fertilization occurs when a sperm penetrates the zona pellucida and fuses with the ovum.
- Recall that cortical granules in the oocyte release their contents immediately after fusion.
- Explain that the released substances modify the zona pellucida to form a zona reaction layer.
- State that this modified zona pellucida prevents entry of any further sperms, thereby avoiding polyspermy.
Common mistake: Thinking the zona pellucida helps additional sperm enter instead of blocking them
Concept tested: Zona pellucida function post‑fertilization
Published · How this solution was prepared and checked
← All Human Reproduction questions