where does the cortical reaction occur?
Answers. Best Answer: The cortical reaction, also known as the zona reaction, occurs when a sperm cell unites with the egg's plasma membrane, altering the zona pellucida which prevents other sperm from binding to and entering the egg.The cortical reaction is exocytosis of the egg's cortical granules.Cortical granules are secretory vesicles that reside just below the egg's plasma membrane.he cortical reaction is exocytosis of the egg's cortical granules. Cortical granules are secretory vesicles that reside just below the egg's plasma membrane.