Fetal Development And Human Development

1376 WordsMar 18, 20166 Pages
Fetal development begins with implantation, when the sperm fertilizes the egg. At this point the fertilized egg is know as a zygote. It splits apart into up to 32 cells which enter the uterus and is then known as the blastocyst. Implantation occurs when the blastocyst begins attaching to the wall of the uterus. From this point the blastocyst is referred to as an embryo until the 9th week of the pregnancy. This 8 week period is called the embryonic period (“Fetal Development”). The first week of the embryonic period differentiation begins to occur. The cells of the embryo multiply rapidly and begin forming different parts of the embryo. The embryo is about 1/100th of an inch long at the beginning of the embryonic period. Blood cells, kidney cells, and nerve cells are forming and a blood vessel has formed. This vessel quickly forms a heart outside of the body still in the first week or so of the embryonic period (Boeree). Later in this first week the brain and spinal cord begin developing as well as the gastrointestinal tract (Storck). In the next two weeks the heart remains outside of the body but beats regularly. The embryo still has a tail but “buds” grow where the arms and legs will begin to form. The spinal cord starts to form vertebra and a larynx or voice box is formed. The brain continues forming and at this point the embryo is about 1/4 an inch (Boeree). The placenta is forming and the embryo is in a sack filled with amniotic fluid keeping it alive (“Fetal
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