Female reproductive system
Activity of female reproductive system is controlled by sex glands: ovaries produced the female sex hormones, such as estrogen and progesterone. Influence of sex hormones is evident in the development of so-called secondary sexual character: constitution, breast, typical female hair pattern.
Hypothalamus and a hypophysis in the central nervous system of the brain serve as the centre regulating ovaries function. Ovaries are the main source of sex hormones in the woman's body. Anatomically, in ovaries two layers can be defined: external with the follicles, and internal. Follicles contain ovocyte. A quantity of female sex cells starting from the teenage age of the girl is gradually decreased. Maturing of ovocyte is accompanied by significant growth of the sex hormones produced mainly in the active follicle. Such changes characterizing the process of preparation for pregnancy can be observed monthly. If the pregnancy does not happen, the menstruation starts, meaning the beginning of a new monthly cycle.
Every menstrual cycle begins from the development of 20-50 follicles containing ovocyte in the ovary. The largest, or dominant follicle can be defined among growing follicles by 8-9th day from the beginning of menstruation. A dominant follicle continues growing and thus depresses other follicles development. The ovocyte grows in a dominant follicle. In a growing follicle, estrogens, female sex hormones, such as estradiol (most active), estrone and estriol are produced. This stage of the cycle is called as follicular. Estradiol content is quickly increased at this stage, reaching the maximum a day before ovulation. In the middle of the menstrual cycle, the dominant follicle releases an ovocyte, this process is called ovulation.
Ovulation causes passing to the following stage of the menstrual cycle, lutein, or the yellow body phase. The yellow body produces other female sex hormone, progesterone.
The yellow body life is 12-14 days and if pregnancy does not happen, by the end of lutein stage, the yellow body stops to function.
Hormones of ovaries (estrogen and progesterone), penetrating into blood, affect the whole organism, providing correct development of genitals, increase in breast, female constitution, voice timbre, and other things.
When the most of follicles is spent, a woman loses ability to conception and menstruation stops. Accordingly, the cyclic fluctuations of sex hormones are stopped and, consequently, level is decreased.
A woman has been menstruating for 30-35 years during her life. The last menstruation, as a rule, is observed at 50-52 years of age. However, this stage may be experienced at 45 or even 35 years of age.
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