Cortical reaction

Cortical Reaction

The Cortical Reaction (pronunciation: /ˈkɔːrtɪkəl riˈækʃən/) is a process that occurs within the egg cell immediately after fertilization.

Etymology

The term "Cortical Reaction" is derived from the Latin word "cortex", meaning "bark", and the Latin word "reactio", meaning "a reaction". The term refers to the reaction that takes place in the outer layer (or "bark") of the egg cell.

Definition

The Cortical Reaction is a series of events that occur within the egg cell after it has been fertilized by a sperm cell. This reaction is triggered by the increase in calcium ion concentration within the egg cell, which is caused by the entry of the sperm cell. The main purpose of the Cortical Reaction is to prevent polyspermy, the fertilization of an egg by more than one sperm cell.

Process

The process of the Cortical Reaction begins when a sperm cell penetrates the zona pellucida, the outer layer of the egg cell. This triggers an influx of calcium ions into the egg cell, which in turn triggers the release of cortical granules. These granules are located just beneath the plasma membrane of the egg cell, and they release their contents into the space between the plasma membrane and the zona pellucida. This causes the zona pellucida to harden and become impenetrable to other sperm cells, thus preventing polyspermy.

Related Terms

Zona Pellucida: The outer layer of the egg cell that is penetrated by the sperm cell during fertilization.
Polyspermy: The fertilization of an egg by more than one sperm cell, which is prevented by the Cortical Reaction.
Cortical Granules: Vesicles located just beneath the plasma membrane of the egg cell that release their contents during the Cortical Reaction.
Calcium Ion: A type of ion that triggers the Cortical Reaction when its concentration increases within the egg cell.