At the female genital system, you ovaries are stimulated by a hormone produced by the placenta, called human chorionic gonadotropin (HCG), and start to function still in the embryonic stage. HCG is a hormone very similar to luteinizing hormone (LH). At birth, a woman has approximately one million primary follicles, also called primordial, on each ovary. Most of these follicles degenerate and a woman reaches puberty with about 400,000 follicles in each ovary.
It is at puberty that a girl begins to produce the main female sex hormones, which are the estrogen and the progesterone. O estrogen is produced in the cells of the developing ovarian follicle, and it is responsible for the appearance of secondary sexual characteristics in women, such as the appearance of breasts, hip enlargement, hair distribution. by the body, etc. Estrogen also induces the maturation of Organs genitals, in addition to promoting the sex drive. THE progesterone is another female sex hormone that is mainly produced by the
yellow body, also called corpus luteum of the ovary. This hormone stimulates the development of blood vessels and glands in the endometrium, thickening it and preparing the uterus to receive the embryo.Once a girl starts producing these sex hormones, once a month she will ovulate, starting her menstrual cycle, which will take place approximately every 28 days. The ovary, at the time of ovulation, releases a secondary oocyte while the uterus prepares to receive the embryo. If secondary oocyte fertilization occurs, the embryo will implant in the uterus and develop, if Instead, it degenerates and is eliminated along with the inner wall of the uterus, in a process called in menstruation. All these processes that occur in both the uterus and the ovary are controlled by the hormones FSH (follicle-stimulating hormone) and LH (luteinizing hormone). Menstruation occurs when the levels of all hormones get too low in a woman's blood, and marks the beginning of a menstrual cycle.
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For educational purposes, we will divide the menstrual cycle into three phases, the proliferative phase, a secretion phase and the menstrual phase.
At proliferative phase, also called follicular phase, the follicle grows and prepares for ovulation. This growth is stimulated by the hormone FSH, and as the follicle grows, it starts to produce estrogens, a group of hormones that stimulate the development of the endometrium. In this process, several follicles are stimulated, but only one of them ends its growth, accumulating fluid inside and transforming itself into a mature follicle or graafian follicle. Upon reaching a certain level in the blood, estrogen begins to stimulate the pituitary gland to release large amounts. of LH and FSH, which will induce ovulation, which usually occurs on the fourteenth day after the beginning of the cycle. menstrual.
At secretory phase, also known as luteal phase, LH stimulates the cells of the ruptured ovarian follicle to transform into yellow body, also called corpus luteum. It is in the corpus luteum that estrogen and progesterone are produced.
If fertilization of the secondary oocyte does not occur, the menstrual phase. In this phase, the corpus luteum degenerates, stopping producing progesterone and estrogen. The drop in the production of these hormones causes the uterus to undergo desquamation, resulting in menstruation, which can last from three to seven days, depending on the woman and her physiological conditions. This drop in the levels of progesterone and estrogen causes the pituitary to produce FSH again, restarting a new menstrual cycle.
The first menstruation occurs at puberty and we call it menarche. After the age of 50, the production of female sex hormones declines, ovulation and menstrual cycles become irregular until they stop completely. At this stage, known as menopause, there is no more reproductive activity in the woman's body.
by Paula Louredo
Graduated in Biology
