The Egg Before and After Fertilization
When a woman ovulates, she releases a mature egg called an ovum, which travels to the fallopian tube where there is a potential place for it to be fertilized. If the ovum becomes fertilized by the male sperm, it means, that conception (the process of becoming pregnant which involves both fertilization and implantation) has occurred.
After conception, the fertilized egg becomes known as a zygote. The zygote is a single nucleus, which contains the genetic material from both parents. Although fertilized, a true pregnancy is not considered to have occurred until the egg has successfully implanted itself in the uterus.
From Zygote to Embryo, Blastocysts and Trophoblasts
After the first cell division of the zygote, the developing baby becomes known as an embryo. The tiny embryo is encased within a thin walled hollow structure, known as a blastocyst, or a cluster of cells. The developing cells on the outside of the blastocyst are known as the trophoblast. They provide nutrition to the embryo. The trophoblast is the part of the blastocyst, which attaches itself to the lining of the uterus and results in implantation bleeding. After successful implantation the trophoblast will become the placenta and continue to nourish the growing embryo. After a period of eight weeks of pregnancy, the embryo is then referred to as a fetus until birth. The foetus (fetus) is the developing, unborn human baby.