Continued from the initial human reproduction page, the previous page in this tutorial.
Upon arrival in the uterus, the zygote fuses itself to the uterine wall. At this point, cells of the zygote differentiate into two distinct types
- Embryoblast Cells - These cells continually divide into what will become the embryo, the baby itself
- Trophoblast Cells - These cells form the placenta, that form against the uterine wall
The placenta is the life support machine of the developing embryo, providing oxygen and food for it and removing toxic material and CO2 from the developing embryo. The umbilical cord, a connection to the mothers' blood stream is responsible for this.
By the end of the third week this placenta provides a rich source of nutrients for the unborn baby that now is roughly the size of this letter o....
Towards the end of the first month, the heart starts to form while designated cells begin to form the basic structure of the limbs, spine, nervous and circulatory systems. After the initial formation of these major bodily areas, less essential characteristics begin to develop such as the eyes, ears and nose.
By the tenth week of pregnancy these facial characteristics become recognisable, and the overall silhouette of the embryo now resembles that of a human.
By the fourteenth week, all the major characteristics of the embryo have more or less developed, and possesses all the requirements of a fully functional being.
From this time onwards, the embryo will continue to grow in size rather in complexity via cell division. Forty weeks later, nine months since fertilisation, the embryo, now in the foetal stage is mature enough to enter the world.
The next page goes through the stages of birth, where the mothers body has to adapt to the harsh conditions of birth...