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Development of the human embryo

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Running Head: DEVELOPMENT OF THE HUMAN EMBRYO Development of the human embryo [Writer's Name] [Institution's Name] Development of the human embryo After about two days the egg has divided to having about eight cells. After four days it is in the uterus and has to "land" somewhere and attach itself to the endometrium. The sperm that penetrates the egg controls gender. Every female egg contains one X chromosome. Every sperm either contains one X or one Y chromosome. To be a male one X and one Y chromosome must be present. To be female two X-chromosomes are present. At the moment of conception the gender is decided. From that point on it can not change. ...read more.


Once it attaches to the endometrium, the primary yolk sac forms. During the next few days the blastocyst divides twice daily. It will contain a couple of thousand cells by the 12th day (Cole, 2003). The beginning of the second week of pregnancy marks a new stage for the embryo. Every single day from this point on until the next few weeks is crucial to proper development in the embryo. The 14th day marks the collapse of the primary yolk sac. This also marks the beginning of week two, when gastrulating begins. According to Webster's Encyclopaedia, ed.1996, "Gastrulating is the process in which post-blastula embryo forms three germ layers, which will differentiate into various structures and organs." ...read more.


The outer cell layer will eventually become the backbone, the brain, and the nerves. This layer also makes the skin, the hair, and sebaceous and sweat glands. (Cole,2003) The middle layer is going to be the lower layer of skin, the bones, and the muscles. Blood and lymph vessels are also made from this layer. Blood cells and the heart muscles make a bloodstream. The sex organs and the kidneys also come from this layer. The inner layer makes up a simple intestinal tube with a mucus membrane. From that tube the lungs and urinary tract form. Everything from all the layers come together to form the organ system. Then the embryo can do a test run with the system. This happens every day while the organs are being formed. ...read more.

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