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Day 1: Fertilization
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. -
Day 3: Division
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. -
Day 9: Implantation
After it gets to the uterus, the fertilized egg attaches to the lining of the uterus, called the endometrium. -
Day 18: CNS formation
The neural groove (future spinal cord) forms over the notochord with a brain bulge at one end. -
Day 23: Heartbeat
the heart begins to beat in Humans. It is the first functioning embryonic organ formed -
Day 32: Growth
Upper and lower limb buds begin growing. The brain continues to develop. -
Day 56: End of Embryonic Period
All major organs are formed now, but they are too immature for the fetus to survive out of the womb.
