Fertilisation

By Zoe Rees

CORONA RADIATA

ZONA PELLUCIDA

PERIVETELLINE SPACE

CELL MEMBRANE

NUCLEUS

HEAD

MID-PIECE FLAGELLUM

PROTECTIVE COATING

NUCLEUS

CapacitationThe protective coating of PROTEINS and GLYCOPROTEINS is removed. This involves ENZYMES found in the uterus.

The sperm is travelling towards the egg, surrounded by the CORONA RADIATA, a membrane.

The sperm contracts the CORONA RADIATA which ruptures releasing PROTEASE ENZYMES

The enzymes DIGEST the ZONA PELLUCIDA surrounding the oocyte.

The sperm travels through the CORONA RADIATA and ZONA PELLUCIDA and into the PERIVETELLINE SPACE.

INVERSION of the ACROSOME results in the formation of a NEEDLE-LIKE FILAMENT.

The needle filament PIERCES the softened oocyte membrane, known as a ACROSOME REACTION. Allowing the head to penetrate.

The entry of the head stimulates THICKENING of the ZONA PELLUCIDA which prevents the entry of other sperm known as POLYSPERMY.

The entry of the head stimulates the completion of the SECOND MEIOTIC DIVISION of the OOCYTE NUCLEUS.

The nuclei of the oocyte and the sperm FUSE together to form a DIPLOID CELL (ZYGOTE)