Menstruation is a physiological phenomenon that is unique to women and is a cyclical physiological change. The periodic changes of estrogen and progesterone, which cause the regular peeling of the endometrium, are the physiological phenomenon that is unique to women – menstruation. The uterus is pictured: The endometrium is in the uterine cavity, which I liken to soil, soil in which flowers can be grown. In fact, every woman, at the time of maturity in her mother’s belly, when she is a small embryo at about 12 weeks, her sexual organs begin to develop and mature, and she has hundreds of initiating follicles developing in her body every month, except that these follicles cannot develop and mature, called follicular atresia, and before atresia, a hormone is secreted in its follicular membrane cells, which is the estrogen that is unique to us women, and for the endometrium Estrogen is like nitrogen fertilizer for the endometrial soil, which promotes the plants in the soil to flourish and everything to grow. Graf follicular estrogen allows the endometrium to proliferate and undergo proliferative phase changes. In a woman’s childhood this trace amount of estrogen promotes rapid growth of little girls, and bone development; by the time puberty comes with menarche, it often prompts – the start of ovulation, and every month, out of the hundreds of follicles that develop cyclically in a woman’s body Often only one will become a superior follicle and develop to maturity, which we call a Graves’ follicle. Every month, from the first day of your period, your ovaries organize a marathon, just like the Beijing Marathon, and many follicles come to run! Each follicle is excited, active and ready to start at Tiananmen Square as the starting point! Some follicle runners take a round of photos with their cell phones, post them to their friends, and go home. These follicles closed down! The rest of the follicles, started to set out to run, but some couldn’t run anymore, and quit after a few kilometers! Also atretic. The final winner is the Graf follicle, and the course of this follicle marathon is about 14 days! (Starting from the first day of menstruation, after 10 days, the mature follicles stand out) After the mature follicles stand out, they start to rupture! Why do they rupture? Because those follicles that drop out, before they drop out, they secrete estrogen! So during the first half of our menstrual cycle, the estrogen in our body is gradually increasing! It increases to 200 pg per ml, and then, our hypothalamus has a feedback and estrogen starts to drop! So here’s the problem – some girls get their periods twice a month and have a small amount of bleeding in the middle of their menstrual cycle, that’s because after estrogen reaches its peak, it feeds back and lets itself drop, the endometrium proliferates under the effect of estrogen, and since it can’t adapt to the drop of estrogen at once, the endometrium will bleed a small amount, which we This is called ovulatory hemorrhage. This can be negligible if the amount is not too much! There is no need to worry! This is an ovary: at the beginning of menstruation, there are many follicles developing, hundreds of them, developing and atresia at the same time, the largest follicle is the Graf follicle, there is an egg in the follicle, the outer circle is called the follicular membrane cells, which can secrete estrogen! When the follicle ruptures, the egg is expelled from the ovary and enters the abdominal cavity. When the follicle ruptures, the egg is expelled from the ovary into the abdominal cavity. A pit forms in this follicle and the granulosa cells along with the blood coming out around it form our corpus luteum! So, during the second half of the menstrual period, progesterone (corpus luteum) begins to make its magnificent appearance, creating a situation where progesterone and estrogen are present at the same time. Progesterone is like a phosphorus fertilizer that prepares the plant for flowering and fruiting! Progesterone makes the endometrium thicker and thicker. If there is no pregnancy, estrogen and progesterone will decline at the same time, the corpus luteum will atrophy, and the endometrium will not be supported by hormones. The endometrium is very rich in estrogen and progesterone receptors, then the endometrium will form an exfoliation and menstruation will form.