cortical granules

Hyalin is a protein released from the cortical granules of a fertilized animal 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.

The cortical granules inside the oocyte then fuse to the outer membrane and a transient fast block reaction occurs.

This electrical signal causes small sacs just beneath the membrane (cortical granules) to dump their contents into the space surrounding the egg.

In the slow block to polyspermy, the cortical granules released from the ovum are deposited in the perivitelline space.

Sea urchin cortical granules regulated proteolysis by cortical granule serine protease 1 at fertilisation.

Interestingly, Munoz-Gotera et al. [ 44 ] showed that calreticulin localizes to cortical granules in guinea pig oocytes and is released into the perivitelline space following activation.

Cortical granules inside the secondary oocyte fuse with the plasma membrane of the cell, causing enzymes inside these granules to be expelled by exocytosis to the zona pellucida.

In the cortical reaction, cortical granules directly beneath the plasma membrane are released into the space between the plasma membrane and the vitelline membrane (the perivitelline space).

It is in this period or in some cases at the beginning of sexual maturity that the primary oocytes secrete proteins to form a coat called zona pellucida and they also produce cortical granules containing enzymes and proteins needed for fertilization.

This itself triggers the cortical reaction, which results in depositing several substances onto the vitelline membrane through exocytosis of the cortical granules, transforming it into a hard layer called the "fertilization membrane", which serves as a barrier inaccessible to other spermatozoa.