The menstrual cycle has two periods which follow each other under the influence of hormones. Right (normal) menstrual cycle has a specific duration of 21 to 35 days. But most of the normal menstrual cycle The normal menstrual cycle: the main feature of women's health   It lasts 28 days.

The first period of the menstrual cycle begins on the first day of menstruation and ends with the beginning of ovulation, which accounts for about the middle of the menstrual cycle. During this period, under the influence of pituitary follicle-stimulating hormone (FSH), and female sex hormones estrogen in the ovary matures the egg enclosed in the follicle. A large number of laid eggs in the ovaries of girls in utero. During each menstrual cycle, only one egg matures in the ovaries of one. But sometimes there are two, and then can be born twins.

What controls the menstrual cycle?

Start of the first period associated with the team coming from the cerebral cortex, which is under the department of the brain responsible for communication of the central nervous system with the endocrine system - the hypothalamus begins to produce hormones folliberin, which stimulates the pituitary follicle-stimulating hormone (FSH). FSH has an effect directly on the follicle, causing it begins to ripen a new egg and follicle epithelium produces the female sex hormones estrogen.

As long as the follicle matures under the influence of estrogen, first restored (after just last menstrual period, during which there was a rejection of the mucous membrane), and then expands the mucous membrane of the uterus. In it, new blood vessels, and glands.

Ovulation

When the egg is fully ripe, its maturity signal enters the central nervous system (CNS), which sends a signal to the hypothalamus. The hypothalamus begins to produce hormones that block the production of FSH and lyuliberin hormone that stimulates the pituitary secretion of luteinizing hormone (LH). The amount of LH increases sharply, and the day after that under the influence of hormonal change of the egg is released from the ovary. This process is called ovulation.

After ovulation, the egg falls almost immediately into the fallopian tube and begins to move toward the uterus. The egg lives only a day, and during this time the sperm must have time to fertilize it. But sperm live longer, from one to three days and can live up to the time of ovulation, even if the sexual act occurred three days before.

The second period of the menstrual cycle

After ovulation begins the second period of the menstrual cycle. During this period, under the influence of LH ruptured follicle is transformed into endocrine gland the corpus luteum, which for the entire second half of the menstrual cycle will produce the female sex hormone progesterone (mostly) and estrogens. Under the influence of progesterone begin to function glands embedded in the mucous membrane of the uterus during the first period of the menstrual cycle. Progesterone also inhibits the contractile activity of the muscle layer of the uterus - you need to in the event of pregnancy to keep a fertilized egg in the uterus.

The egg continues to move toward the uterus. If it is fertilized by sperm, the movement continues germ that enters the uterus in a week after fertilization and is embedded in the mucosa. Initially, this is superficial, loosely, and then his uniform jacket grows blood vessels to the wall of the uterus and on the site of the placenta attachment gradually formed, which with time (approximately 16 weeks of gestation) will take over the entire hormonal function. In the meantime, female hormones continues secreting corpus luteum, which is growing, is transformed into the corpus luteum of pregnancy.

If pregnancy has not occurred

If pregnancy does not occur, then under the influence of hormones, he entered the egg in the uterus in the figurative expression of some obstetricians "born with a mucous membrane is torn away." This occurs due to the fact that in the CNS signal is non-pregnancy, this signal is transmitted to the hypothalamus, which terminates lyuliberina hormone secretagogues stimulate secretion of LH by the pituitary gland. The pituitary gland stops secrete LH, resulting in the corpus luteum does not secrete female hormones. The mucous membrane of the uterus, deprived of hormonal support, rejected that accompany the next menstrual bleeding.

On the first day of the menstrual cycle The menstrual cycle - that occurs in different phases?   It begins a new egg maturation, as hormones change again - begins the first period of the next menstrual cycle.

The menstrual cycle of women - a clear mechanism that allows it to have a baby. The slightest failure of this mechanism may be to deprive it of such a possibility.

Galina Romanenko

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