Fertilization is the fusion of a sperm with an ovum in the oviduct (also called the fallopian tube.)
During sexual intercourse, thousands of sperms are released into the vagina by the penis.
Sperms swim through the cervix into the uterus up to the oviduct.
Few sperms that reach the ovum try to penetrate it.
Only one sperm penetrates the ovum.
When the sperm penetrates the ovum, the surface of the sperm fuses with the nucleus of the ovum to form a zygote.
The zygote moves from the oviduct and enters the uterus, attaching itself to the uterus walls.
This process is called implantation.
Once implantation has taken place, the zygote is now referred to as an embryo.
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