Fertilization is the encounter between a sperm from the father and an egg (oocyte) from the mother. This fertilization is at the origin of the formation of an embryo, then of a fetus which will develop in the maternal uterus.
During intercourse at the time of ovulation, there is a good chance that there is fertilization (if no particular means of contraception is used). During ejaculation, millions of sperm "panic" to the uterine horns, to meet the egg. But only a very small proportion of them will reach the end ...
During fertilization, the protective membrane surrounding the egg will be partially destroyed by the sperm that seek to penetrate. Generally, only one sperm manages to enter. He will then instantly make a chemical barrier to prevent the penetration of other sperm.
Fertilization - this encounter between a spermatozoon and the egg, will lead to a multitude of biological reactions, with the formation of a single cell (the egg) that will very quickly multiply to lead to the development of an embryo.
50% of the father, 50% of the mother
Spermatozoa and oocytes are the only cells in the body that contain only 23 chromosomes instead of 46. The 23 chromosomes contained in the spermatozoon (carriers of the characteristics of the father) will fuse with the 23 chromosomes of the ovum (characteristics of the mother) to form the baby's first cell, which will include 46 chromosomes.
This first cell will then split to form two separate cells. These two cells will then themselves duplicate, and so on ...
The egg thus formed (we do not really yet speak of an embryo), will then leave the proboscis to go little by little in the womb, where it will nestle and finish its growth: this is the " nidation ". It will become after a few days an embryo, then a fetus, and finally, a baby.