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The sperm penetrates the egg.
It takes about 24 hours for a sperm cell to fertilize an egg. When the sperm penetrates the egg, the surface of the egg changes so that no other sperm can enter. -
The Cells Start to Divide. The fertilized egg starts growing fast, dividing into many cells. It leaves the fallopian tube and enters the uterus 3 to 4 days after fertilization.
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After it gets to the uterus, the fertilized egg attaches to the lining of the uterus, called the endometrium.
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The neural groove (future spinal cord) forms over the notochord with a brain bulge at one end.
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the heart begins to beat in Humans. It is the first functioning embryonic organ formed
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Upper and lower limb buds begin growing. The brain continues to develop.
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All major organs are formed now, but they are too immature for the fetus to survive out of the womb.
