People would hardly argue that the birth of a new life is in essence a great miracle. Thanks to the progress and development of technologies, during the 9 months period we can sometimes “take a peek” at the future child’s growth and development. However, there is a specific space of time, when no one is able to see it despite the fact that the development process has already started. This is the mysterious first week of pregnancy. So what happens to an egg-cell during the next week after the insemination? Let’s lift the veil of mystery.
So, How Does the Future Baby Evolve During the First Week of Pregnancy?
Once the core of the lucky sperm merges with the nucleus of the stormed egg-cell, a zygote (a single-celled embryo with a complete set of chromosomes) is formed. The zygote begins to move from the ampullary portion of the tube towards the uterine cavity, carrying the entire genetic package needed for the development of a future of human being. About a day later the zygote splits for the first time into two cells, blastomeres. On her way there zygote travels like a queen surrounded by a gradually decreasing army of sperm unsuccessfully attacking the now firmly closed target. The splitting egg does not have its own organs and functions of the movement, it needs the energy for something more important, so it is delivered to the uterus by the periodic wavelike contractions of the fallopian tubes, cilia (a very small hair) movements of the tube cavity epithelium lining and capillary fluid flow. Only the coordinated work of all of these components can provide efficient transportation of a fertilized egg.
On the 4th – 5th day of its existence, the zygote reaches the uterus. It is already composed of several dozens of blastomeres (embryonic cells), which are becoming smaller with every splitting. The embryo is still not connected with the mother’s body, so before it implants it’s nourishment is provided with its own resources, thanks to the various nutrients and enzymes contained in the cytoplasm . Besides, the general idea is that the egg shell is able to absorb various elements from the fluid produced by the mucous membrane of the uterus.
At this stage,inside the egg appears a cavity filled with water. This pressure on the dense outer wall of the shell coming from the inside of it makes it become thin and tear. Otherwise it would not have allowed the embryo to implant. Blastocyst, this is how an embryo at this stage is called, now slowly comes out of the egg through the gap and starts preparing for implantation, which most often occurs on the 7th day after fertilization. Now the future embryo looks like a ball with an inside cavity filled with liquid and an isolated group of embryonic nodule cells on the one of its poles. The blastocyst outer shell, called trophoblast, grows special spurs, which it uses to attach itself to the uterine wall.
The first week results in one of the most important and crucial events of pregnancy – the embryo’s introduction into the uterus lining, in other words, the implantation. The trophoblast spurs begin producing special enzymes that allow them to sligtly melt the endometrium and make a small and cozy cavity for the embryo in the uterus lining. After that, the uterus lining grows back over the blastocyst. It now appears completely immersed in the endometrium, rich with a special secretion containing a lot of different biologically active compounds, necessary for the further development of the embryo. The whole implantation process can take up to two days. Now nourishment for the embryo would be provided by the mother’s body up until it’s birth.
As soon as the embry shell spurs grow into the blood vessels of the uterus wall, the human chorionic gonadotropin (hCG) hormone starts getting into the mother’s bloodstream. After a while the woman will get an ability to learn about a new life growing inside of her with the help of a pregnancy test or a special blood test. This very hormone also gives a signal of successful embryo implantation to the yellow body, encouraging it to further produce progesterone – a hormone responsible for maintaining pregnancy.
This is the first week of a soon-to-be human’s life inside the uterus. More of such weeks await ahead of him or her, but this period is the earliest and can be compared to the foundation laying of a building. Besides, it becomes clear that it is impossible to determine pregnancy in the first week, regardless of the wishes of many women who are planning to have a baby. First signs of pregnancy might make themselves known no sooner than the complete implantation of the embryo into the uterus and completion of the strong bond with the mother’s body.