Physiology: The fertilization and implantation.
After ejaculation, the sperm remains in contact with the mucus, with whom he has been more or less mixed.
Because of the preovulatory estrogen peak, the mucus has a maximum at this point its qualities of receptivity (abundance, spinnbarkeit, clarity and other physicochemical characters) sperm leaking vaginal acidity.
Male gametes (sperm) can live for several days in a mucus excellent and seem to congregate in the crypts of the endocervix (improperly called glands), where they are gradually released into the uterus and fallopian tubes .
The movement of the sperm into the cervix, the uterus and fallopian tubes light is poorly understood, and it is not only because of their motility, as there are sperm in the fallopian tubes after a few minutes report time too short they cross themselves the considerable distance too, uterine and tubal kinetic Have a role.
During this trip, sperm acquire their fertilizing ability through a process of “empowerment” in contact with the mucus and mucosal genital mutilation. The dead sperm are reabsorbed at the mucosa, mainly in the endometrium.
After the discharge of the pituitary hormone LH in the fourteenth day of a cycle of twenty-eight days, it is an opening on the mature ovarian follicle, through which the follicular fluid flows into the peritoneum causing oocyte .
The corpus luteum that forms on the ovary secretes very quickly from progesterone , which, among other biological actions, will cause thermal drift and lose the mucus receptor properties.
Upon issuance, the oocyte is surrounded by a ring of granulosa cells (corona radiata) and did not complete its maturation: it is the stage of oocyte II with 23 chromosomes (22 + X A), after having issued its first polar body, and enters its final maturation mitosis.
It is driven by a current of peritoneal fluid to the external orifice of the tube, which is also close to the ovary by scanning the surface with the fringes of its flag. The egg in the tube migrates under the action of the cilia of the tubal epithelium and peristalsis, and is freed from its corona radiata during the route.
The meeting of sperm and oocyte seems to be in the outer third of the fallopian tube.
The sperm also carries 23 chromosomes (22 + X A, or 22 A + Y) penetrates the ovum which completes its final maturation mitosis and deliver its second polar body. The sperm binds to specific receptors on the zona pellucida of the oocyte and the cross, and merges with the plasma membrane of the egg; nuclei (pronuclei) male and female accolent to reconstruct an egg at 46 chromosomes, the sex is determined by the capital chromosome sperm.
The progestational period is six to seven days during which the egg formed leads a free life. It divides rapidly and has tripled in size when it enters the uterine lumen at the morula stage after three to four days to cross 6 to 8 inches apart in that.
The morula then remains free in the uterine lumen for three additional days during which she spent at the blastocyst stage three tenths of a millimeter in diameter.
Implantation and early pregnancy
The blastocyst comes into contact with the endometrium (uterine lining), in which he enters the ninth day after fertilization or to the 23rd day of a 28 day cycle, because the egg is fertilized for only a few hours.
Its rudimentary trophoblast (the precursor of the placenta) very quickly secretes HCG, whose detection is the basis of pregnancy tests , which will stimulate the corpus luteum: far from drying up the secretions progestogen latter will increase steadily and maintain the endometrium in place: amenorrhea is pregnancy.
It should be noted the essential role of the corpus luteum and its hormonal secretions, both during the progestational (tubal contractions, nutrition egg free by genital secretions) that during implantation (proper preparation of the endometrium) the beginning of pregnancy.