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Streaming Video, 2013
Current format, Streaming Video, 2013, , Available .
Streaming Video, 2013
Current format, Streaming Video, 2013, , Available . Offered in 0 more formats
About 24 hours after fertilization the zygote divides into two cells. Some 15 hours later, the two cells divide to become four. At the end of three days, the fertilized egg cell has become a berry-like structure made up of 16 cells. This structure is called a morula. For eight or nine days after fertilization, the cells that will eventually form the embryo continue to divide within the fallopian tube. The blastocyst, a hollow structure formed by the cells, is slowly carried toward the uterus by tiny hair-like projections called cilia. The blastocyst, though only the size of a pinhead, is composed of hundreds of cells. During the critically important implantation process this structure must attach to the uterine lining, or the pregnancy will fail to survive. If the blastocyst buries itself in the uterine lining, it will obtain nourishment from the mother's blood supply.
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