Fertilization And Implantation

Fertilization is the biological process released during a sexual intercourse. In this process, semen containing thousands of sperm is inseminated into the vagina. After the penetration and with the help of reproductive parts sperms start to clear their route in the fallopian tube to meet the ovum. More distance it covers, sperm count reduces and very few sperms reach the egg. An egg is covered by a protective layer called zona pellucida. Sperms modify themselves and start to release chemicals in order to attract the egg and penetrate into it. Upon encountering the egg, the sperm releases its content inside the egg and fuses with the egg nucleus. Fertilization is accomplished in this step. Out of thousands, mostly only one sperm accomplishes its target.

Timing is everything. Both sperm and egg can show their vitality only to a limited period of time. A sperm is alive for 48-72 hours in a female reproductive system whereas the egg can be fertilized until 24 hours from its release. This answers the question how a sexual intercourse leads to pregnancy. However, not every intercourse leads to pregnancy.


Once fertilization happens, the cell starts to divide and multiply within 24 hours at the fallopian tube. This detached multi-celled structure is called zygote. Later, after 3-4 days it travels to the uterus and now we call it as an embryo. The embryo develops and undergoes various stages and gets attached to the endometrial layer of the uterus. This process of attachment is known as implantation. Officially a woman becomes pregnant.

fertilization and implantation

Sex determination

Fertilization is the process in which new cell is formed when two gametes (sex cells) –sperm and ova are fuse together. During this unbiased event, all genetic information is transferred from both the parent to their child and gender of the child is determined. Father determines the sex of the child i.e. if the sperm carries Y chromosome, the child will be a boy; if sperm carries X chromosome child will be a girl.

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Practise This Question

The sex chromosomes of a human female are