First menstruation appears aged 10 - 16 years. Since then the body is considered to be capable of conceiving and nurturing pregnancy. In 45 - 55 years old, this function begins to gradually fade away and menstruation ceases. This period is called menopause.
The first day of the menstrual cycle is considered the first day of menstruation, the last - the day before the start of the next menstruation. The cycle time for all women are different. Normally, it lasts 21 - 35 days, in most cases - 28 days.
The first phase of the menstrual cycle (follicular) occupies a large part of it. Thus, of the 28-day cycle, it comes first 14 days. In the blood, with the advent of this phase, brain cells start to secrete the hormone. This is preceded by a series of complex biochemical processes. This hormone stimulates the ovaries, causing them to increase in number of follicles simultaneously.
Follicles begin to grow at the same pace. Then, one advances in the growth of the rest becomes dominant. Then the remaining follicles, slowing down the growth rate, again turning to its initial state. The dominant follicle grows and actively growing, sometimes reaching 2, 5 cm in diameter. It serves as the production and release into the blood "female" hormone - estrogen.
Estrogen in the female body performs many functions. It helps to improve blood flow to the uterus, increases sexual desire of women at the time of exit from the egg follicle, allowing implement inherent in the female body process of conception. This hormone is capable of reducing the viscosity of mucus in the channel of the cervix, which facilitates the penetration of sperm into the uterus.
By increasing the content of estrogen in the blood up to a certain level, the brain produces luteinizing hormone, which causes ovulation ie rupture of the follicle and release of the egg. This process is in the middle of the cycle. To get into the uterus, the egg gets released into the channel through a thin branch of the uterine tube. Under the influence of estrogen, it clings to the surface of the ovary in the place where there was a rupture of the follicle.
To get to the egg uterus, fallopian tubes begin to shrink, thus creating fluctuations special cells. They will move the egg into the uterus. Moreover, the entire process takes place with a certain duration. After all, if he accelerates, the egg leaves the uterus prematurely, not merged with the sperm. When decelerating same fertilized egg will attach to the uterine wall is not, and to the pipe. Normal flow of these processes are accompanied by the health of the reproductive organs of women and slender work hormones.