How is the fertilization envelope formed?

Answer 1

The fertilization envelope is formed after sperm entry into the egg, triggering a series of events known as the cortical reaction. Upon fertilization, cortical granules in the egg release their contents into the space between the egg membrane and the vitelline layer, leading to modifications of the egg's extracellular matrix. This process hardens the outer layer and creates a protective barrier that prevents additional sperm from entering, thus ensuring that only one sperm fertilizes the egg. The formation of the fertilization envelope is crucial for preventing polyspermy and protecting the developing embryo.