D3 Events of Fertilisation, IVF SL

Capacitation

Physiological changes undergone by the sperm in the female reproductive system that lead to their activation and, eventually, fertilisation of the egg.

Egg activation

The process initiated by the penetration of a sperm into the egg, resulting in metabolic changes (the rise of intracellular calcium levels and the cortical reaction) that prevent polyspermy and trigger meiosis II, leading to the formation of female pronucleus.

Cortical reaction

A process that happens right after a sperm enters the egg (part of egg activation). It releases cortical granules from the egg’s cytoplasm into the space outside the plasma membrane, making it hard. This prevents polyspermy as other sperm can’t get in. This is triggered by the influx of calcium ions after sperm’s fusion with the egg.

Pronucleus (male or female)

The haploid nucleus of the sperm/egg before the formation of the diploid zygote nucleus.

Acrosome reaction

Part of the fertilisation process where the acrosome of the sperm that reached the egg releases enzymes that digest the zona pellucida so the sperm can reach the egg’s plasma membrane.