Prembryo Culture-IVF-Missouri Center for Reproductive Medicine & Fertility

Following penetration by sperm, the egg is one cell containing the female pronucleus with the genetic material from the egg, and the male pronucleus with the genetic material from the sperm. This is the two pronuclei (2PN) egg, called a zygote. The zygote is a single cell containing genetic material from both the mother and the father. Fertilization is not complete until the two pronuclei merge to form the nucleus of the pre-embryo.

The fertilized egg undergoes divisions called cleavages. It divides into two cells and from there eventually into 6-8 cells. Each cell in these cleavage stage pre-embryos is called a blastomere. Actual image of a fertilized egg with the male pronucleus and female pronucleus labeled within the egg. The zona pelllucida, polar body and a non-fertilizing sperm are also labeled.

Actual image of a fertilized egg with the male pronucleus and female pronucleus labeled within the egg. The zona pelllucida, polar body and a non-fertilizing sperm are also labeled.

Actual picture of an 8-cell embryo with one cell labeled blastomere

Picture above: micrograph of a zygote or 2-PN Stage preembryo; PN stands for pronuclei Picture above: micrograph of an 8-cell preembryo with eight blastomeres Actual image of a blastocyst with labeling:the trophoblast, which gives rise to the placenta, the Inner Cell Mass, which gives rise to the embryo, and the thinning zona pellucida ready for hatching.

Actual image of a blastocyst with labeling:the trophoblast, which gives rise to the placenta, the Inner Cell Mass, which gives rise to the embryo, and the thinning zona pellucida ready for hatching.

Picture above: micrograph of a blastocyst at 5 days of culture