Please note: This article contains sexual health content and it is purely made for educational purposes.
Fertilization is the process of fusion of two different types of sex (male and female) cells and developing a new organism from that fusion cell. Fertilization happens in every common species like plants, animals, and humans. But fertilization in humans is much more complicated and it is a needed one, to sustain our race. Let’s see about the process in detail.
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Sperm and an Ovum |
Human fertilization occurs only in women, where she gives birth to a child from a single cell (ovum or egg cell) in her body. But to make the women get fertilized (i.e., to give birth to a child) a man is required, who delivers another type of cell (sperm cell) for the fertilization. So, when the sperm from the man and the ovum from the woman got fused in the woman’s body, fertilization occurs and that fusion cell develops into a full-form baby. Only the sperm can get to the women’s body for fertilization, and not the ovum to the sperm.
This fertilization occurs in the reproductive system of the women, where the baby develops. Both male and female have their own reproductive system which is mainly used for producing their sex cells (sperm and ovum) for reproduction purposes.
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Credit: By Baresh25 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=62622694 |
The above diagram shows the anatomy of the male and female reproductive systems. The testicles are the important part of the male reproductive system, which produces the sperms; and the ovaries are the important part of the female reproductive system which produces the ovum. The process of sperm production in the male is called spermatogenesis whereas the process of ovum production in the female is called oogenesis. Both the systems perform various processes to produce their sex cell. The process of spermatogenesis and oogenesis has been clearly explained in my previous post. Please click the below links to see the process.
The female reproductive system ejects an ovum every month from the ovary owing to be fertilized by the sperm. If the ovum is not fertilized, then the ovum will be lost as menstruation, which we call it as the period. But in the male reproductive system, sperms are produced daily. Every day, millions of sperms are produced at the rate of 1500 per second. The ejection of sperm from the male body is called ejaculation. Now when an ovum is ejected by the ovary during ovulation, it is made to pass through the fallopian tube.
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The small tiny projections, known as Cilia cells in the fallopian tube, move the egg along the way. At this time, when the woman had the sperm gets inserted into her vagina by sexual intercourse, it travels across several obstacles and reaches the ovum. On the way through its journey, several million sperms die due to the environment present in the female reproductive system. But still, some of them survive due to the fluid present around the sperm. After crossing several obstacles, the sperm reaches the ovum and it crosses two main gates named as corona radiata and zona pellucida. After that, the sperm embeds on the surface of the ovum. After embedding, the sperm’s packed genetic material unwinds and becomes a pronucleus. Meanwhile, the women’s DNA does its final division and becomes a pronucleus. Now both the pronucleus shares its DNA (1N1C, 23 chromosomes each), and becomes a single DNA (2N2C, 46 chromosomes). Once the DNA has been mingled, the ovum and the sperm will be together called a zygote. Now the zygote will produce certain chemicals that will destroy all other sperms that are outside the zygote to prevent further entry into the egg.
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Fertilization process |
Now the zygote flows along the fallopian tube by the movement of the cilia cells and falls into the uterus path. On the way through its journey that single cell starts to grow by going under the mitotic division. The mitotic division is a kind of division, where one cell is duplicated into another; thereby each cell will be genetically identical to the other. To know more about the mitotic division, and the number of chromosomes, please visit the following link.
The cells start to divide rapidly and become a blastocyst. The blastocyst attaches to the lining in the path which was developed especially for it. This lining is made, when there is an ovulation. This blastocyst then embeds under the lining and transforms into a full-grown baby. This process will take up to 7 to 10 months. The baby gets all its nutrients through the umbilical cord which is connected to the blood vessels through the placenta. When the baby is removed the placenta is also removed together.
As we saw, that human fertilization is a complicated one. The combination of the sperm and ovum can take place in different forms which result in different varieties of babies, called twins. But as you think, twins are not the same types of babies born together. There are different types of twins, which we can discuss in the next post.
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