Why do girls have menstruation?
Menstruation is part of the menstrual cycle. Their favorable course is the main sign that the health of the girl is good. During menstruation, the volume of blood lost is up to 150 milliliters.
How do menstruations begin?
The main reason why girls have menstruation is the lack of pregnancy and endometrial rejection, which was prepared for the adoption of a fertilized egg.
At some point, the brain sends a hormonal signal, and one of the ovaries, having accepted it, also begins to produce hormones. Under the action of estrogen, the egg, which is located inside this ovary in a special follicle, begins to mature. In the middle of the menstrual cycle, the follicle bursts. The mature egg enters the abdominal cavity (the period of ovulation), and then begins to move along the fallopian tube into the uterus. If fertilization does not occur along the way, then it dies. This is the follicular phase.
Cause of menstrual bleeding
Then comes the luteal phase.In place of the follicle, a corpus luteum is formed, which produces the hormone progesterone. Thanks to him, the blood supply to the uterus is improved. Since the pregnancy has not come, the level of progesterone drops, which leads to a narrowing of the arteries of the uterus. Endometrium is rejected, which is why girls have menstruation.
This whole process is accompanied by rupture of blood vessels and vaginal bleeding. All this suggests that the girl entered the final period of puberty and became a girl who is already able to give birth to a child. For the first time, menstruation can begin at about 12–14 years old, but this framework is relative, since each girl has her own body characteristics.
At first, monthly periods may be uneven, non-permanent, but over time they normalize. The reason why girls go for menstrual periods of a different number of days is explained by the physiological characteristics of the body: menstruation lasts from two to seven days. Experienced emotional stresses, frequent overwork, existing diseases of the reproductive system can affect the change in their duration.
So, you know why girls have periods. They are a normal biological process for every girl. A few days before their occurrence, some signs may appear, for example, swelling of the mammary glands, changes in blood pressure, as well as mood changes, irritability over trifles, aggressive behavior. This phenomenon is called premenstrual syndrome - PMS.