In vitro fertilization (IVF)
This represents the main laboratory stage of your attempt. A few hours following the egg collection the embryologist places a specific number of motile spermatozoa in the culture dishes containing the eggs.
In conventional IVF there is no further intervention.
The spermatozoa approach the egg on their own and one of them penetrates it and fertilizes it.
In more detail, the spermatozoa digest the layers of granulosa cells, meet the oocyte, attach on the zona pelucida, and only one sperm enters the oocytes.
The oocyte reacts to the penetration of the spermatozoon. First, the zona pelucida and cell membrane change their consistency to prevent the entrance of more sperm. Second, the oocyte resumes the second meitic division and extrudes the second polar body. Simultaneously, the male and female pronuclei form and become visible, marking the fertilization of the oocyte.