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Fertilization


Definition:

As fertilization (Latin fertilitas = fertility) or fertilization, the union of sperm cell and ovum is called, while consequence the zygote originates. Due to the fusion of the nuclei of both germ cells, the zygote now has a complete, diploid set of chromosomes, with a total of 46 chromosomes (only in humans!). Only with the genetic material of father and mother, the fertilized cell can begin with the cytokinesis, since the previously haploid chromosome set of both germ cells (23 chromosomes each) would lead to an uneven distribution of the chromosomes in a cell division.
By the way: The terms used in everyday lifeEmpfдngnis' and 'procreation'also refer to successful fertilization.

Course of fertilization

1.) After ejaculation, the sperm move through the woman's vagina. The majority of sperm die before reaching the egg on the way through the acidic vaginal environment and the hard permeable cervical mucus in the cervix. Not fully functional sperm do not make it to the cervical canal and are so selected.
2.) Each month, several oocytes mature in the ovaries, of which only one is ultimately ejected. Excessive oocytes absorb the body relatively quickly. The unfertilized egg migrates through the fallopian tube to the womb (duration: about 3 days). However, the ovum is only fertile for about 10 hours. If the spermatozoa is not fertilized within this period, the body will react later with the obstruction of the buccal mucosa (menstruation).
3.) Only 100 - 1000 sperm reach the fallopian tubes at all. As soon as the head of a sperm hits the egg cell, enzymes on the head cap dissolve the oocyte membrane (acrosome reaction) so that the sperm together with its own nucleus can enter the egg (fertilization). The oocyte reacts first with a reversal of the membrane potential, and subsequently with the membrane's predilution, to prevent the entry of further sperm.
4.) The haploid nuclei of both germ cells (simple chromosomes) merge into a diploid chromosome set.
5.) Via the fallopian tube, the fertilized egg cell moves on to the womb, where the implantation (nidation) takes place.