As fertilization occurs ?
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natural fertilization of the egg by sperm occurs after sexual intercourse during ovulation in women.At the time of ovulation (this period takes from 24 to 27 hours) ripened egg enters the fallopian tube and meets the sperm, they are connected - so that conception occurs.
As fertilization occurs in normal conditions
Let's examine what happens at fertilization.In the middle of the menstrual cycle, just before the onset of ovulation, the vagina moist created a favorable environment for sperm.At the time of ovulation of follicles present in the ovary into the abdominal cavity of the egg comes out, ready for fertilization.She moves to the fallopian tubes using a lint that "pushed" her fallopian tubes.The egg fallopian tubes will be on during the day, waiting for fertilization by sperm.
At the same time only at a single ejaculation in the female body gets up to 250 million sperm.But to reach the egg and fertilize it can in most cases only one - the fastest and hardy.The shortest time in which the fertilization takes place, like any average woman - from 3 to 6 hours.It is this gap requires the microscopic sperm to pass its way from the vagina to the fallopian tube, and it is approximately 15 cm.
Due to the fact that sperm can remain viable for 5-7 days in a woman's vagina, fertilization may occur some time after ejaculation.Consider the situation when ovulation should occur on the 14th day cycle, and unprotected sexual contact took place on the tenth day.All this time the vagina live sperm, and at the right moment, when the female body releases a mature egg, one sperm "breaks" to her, and they coalesce.So to say exactly what day of fertilization occurs, it is almost impossible.This can only be judged if you know for sure when ovulation occurs.
moment of fertilization
As fertilization occurs in terms of the science of biology?The egg is fertilized by the sperm penetrated into it, which transfers the egg paternal genetic material.
When the sperm reaches the egg, fertilization can make only one of them, as the egg is just "not allow" to get into it a greater number of sperm.Sperm thus produces lysis (dissolving) enzymes that destroy the skin a female egg, which allows him to get inside.Once fertilization has occurred, its membrane becomes very thick due to the special arrangements that run at the biochemical and molecular levels.These processes provide protection against the penetration of sperm into the egg other.
Since the male and female sex cells (gametes) at its core have only half the genetic set (23 chromosomes), after gamete fusion occurs compound nuclei, and after that formed a fertilized egg, now called a zygote.
whether double fertilization is possible?
The egg is one nucleus with 23 chromosomes, so it can merge with a single sperm.The above describes how the female gamete is protected against the ingress of a greater number of sperm.However, sometimes it happens that the cell enters more than one sperm.
However, natural mechanisms regulate everything so that double fertilization occurs rarely.The "extra" simply are reduced sperm (die) and are ejected without bringing with it any harm.In very rare cases, if certain processes went "wrong" with the egg nucleus can merge two or more sperm.It says the insolvency of female gametes - a zygote in this case will not develop and reduced.
How then formed multiple pregnancies?There are two options.
- first - ripening of two or more eggs.Then they each fertilized individually according to the diagram shown above.In addition, each child will have their own individual set of chromosomes.In fact, it will be just brothers / sisters who are born on the same day, they will be called polizigotnymi twins.
- second option - this is where, for whatever reason (these factors are still up to the end of the unknown to science), in the early stages of development of the zygote divides into two identical, which contain the same genetic material, and the light at the same time will be identical (monozygotic, identical) twins.They can be only one gender - either boys or girls.
Fertilization - is an amazing process, which demonstrates the emergence of a new life at the cellular level.You can see a lot of video on the Internet on how fertilization takes place, one of which you will find on this page.