In this article we will respond to where fertilization occurs, and other issues such as when is the best moment, the process, what are the mechanisms that must be given, the tiempo what usually takes after intercourse, or even what is assisted fertilization.
We hope to solve your doubts without being too technical, but some medical or scientific terms we must use.
Definition of fertilization
Fertilization is defined as the process by which two sex gametes, one male and one female, unite. This union enables the creation of a new life. This is a complex procedure that requires a series of optimal conditions. This process not only occurs in the human species, but is shared by animals, mammals or not.
In the case of people, the fertilization process occurs in the interior of woman's bodyFor this, it is necessary for the woman to be in a specific phase of her menstrual cycle. And that during intercourse ejaculation occurs inside the vagina.
The specific phase in which the woman must be to be fertilized is when the mature egg leaves the ovary and is in the fallopian tube. In a regular cycle this happens around day 14. Of all the millions of sperm that are ejaculated, approximately 200 reach the fallopian tube and only one of them will manage to cross the outer membrane of the ovum and fuse with it.
Sperm have a survival of approximately three days at this location. That is why it is said that this fusion can occur between 19 and 72 hours after sexual intercourse. But times can vary so much between some cases and others that it is not possible to give a specific time.
How is the proccess?
The fertilization process can be divided into four stages:
- Penetration of the radiated crown. The sperm has to penetrate the layer of cells that surrounds the egg. This is the corona radiata.
- Penetration of the zona pellucida. At this stage, the sperm head makes contact with the ZP3 receptor in the zona pellucida of the ovum. This union releases enzymes that allow the passage of sperm.
- Membrane fusion. The sperm comes into contact with the plasma membrane of the egg. In this stage there are 3 processes in the female gamete: formation of the fertilization cone, depolarization of its membrane and release of cortical granules.
- Nucleus fusion and zygote formation. Here the sperm advances until its head is next to the female pronucleus and, once they are next to each other, fusion occurs. The membranes of both disappear, so their chromosomes can come together and there is a new cell with an initial chromosome endowment from both parents.
The zygote, which is in the fallopian tube, will advance for three or four days pushed by the muscular impulses of the tube until it reaches the uterine cavity. These days cell division has already started and the small embryo will adhere to the endometrium. Here it will develop and grow until the moment of delivery.
Assisted fertilization
As you can see, natural fertilization is not as simple as we imagine. A series of circumstances have to occur and it is not always easy. Sometimes getting pregnant can be complicated. Therefore, science allows us the possibility of assisted reproduction. This is a set of medical techniques and treatments aimed at achieving a pregnancy when natural fertilization is not possible.
When we talk about assisted fertilization we are not only talking about medical fertility problems, but it is increasingly a technique that women, who want to be mothers, and do not have a partner, or the partner is of the same sex, resort to.
There are different assisted fertilization treatments, it can be by artificial insemination (AI), fertilization vitro (IVF), egg donation, embryo transfer or embryo-reception. Each of them has its applications and its peculiarities.