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The fertilization envelope is formed by the lifting of the vitelline envelope away from the egg plasma membrane. The cortical granules contain enzymes that aid in the detachment of the vitelline envelope, as well as other components that aid the osmotic swelling of the fertilization envelope away from the egg.
Keeping this in consideration, what does the cortical granule do?
Cortical granules are regulatory secretory organelles (ranging from 0.2 um to 0.6 um in diameter) found within oocytes and are most associated with polyspermy prevention after the event of fertilization. This exocytosis of cortical granules is known as the cortical reaction.
Likewise, how do cortical granules prevent Polyspermy?
To prevent polyspermy, the zona pellucida, a structure that surrounds mammalian eggs, becomes impermeable upon fertilization, preventing the entry of further sperm. The structural changes in the zona upon fertilization are driven by the exocytosis of cortical granules.
After the sperm enters the cytoplasm of the oocyte (also called ovocyte), the tail and the outer coating of the sperm disintegrate and the cortical reaction takes place, preventing other sperm from fertilizing the same egg. The sperm nucleus then fuses with the ovum, enabling fusion of their genetic material.