“The second seventh day of the year and the heavenly sperm arrives, the Ren pulse is open, the Taichong pulse is full, and the menstrual events take place at the right time, so there is a child.” The “menstrual event” is menstruation, also called “aunt” or “old friend”. A healthy woman will have vaginal bleeding (actually uterine bleeding) once a month for 3 to 7 days, and this periodic vaginal bleeding is menstruation. Menstruation is a special physiological phenomenon for women and an important sign of the development and maturity of the female reproductive organs. The term “menstruation” is a medical term, and there are various names for this physiological phenomenon: some commonly call it “aunt”, some affectionately call it “old friend”, and others call it “menstruation” or “menstruation”. It is also a sign that the female reproductive organs are mature and that the uterus and ovaries are functional. It is also a sign of the maturity of the female reproductive organs and the ability of the uterus and ovaries to function, indicating their natural fertility. Why does menstruation occur? This begins with the function of the uterus and ovaries mentioned earlier. In a normal woman, all of her egg cells are produced in the fetal stage, with hundreds of thousands of primordial follicles. During female growth and development, most of the follicles die and only a few survive to adolescence. Under the control of the hypothalamus, the anterior pituitary gland secretes a hormone (follicle stimulating hormone) that causes the follicles to mature and synthesizes and secretes estrogen. In response to estrogen, the endometrium begins to proliferate and there is a peak in the secretion of follicle stimulating hormone and luteinizing hormone one to two days before ovulation. Immediately afterwards, estrogen levels begin to decline and the follicles mature and ovulate. After ovulation, under the action of progesterone, the proliferative endometrium changes to a more fluffy secretory endometrium, ready for the fertilized egg to come and settle down. If the discharged egg can be courted by sperm and conceived to form a fertilized egg, it will continue to develop into an embryo and fetus until delivery; if the egg is not conceived, the corpus luteum begins to atrophy and the secretion of progesterone and estrogen rapidly decreases. The endometrium suddenly loses the support of these two hormones and the blood vessels contract, causing the endometrium to atrophy, necrotize and shed, resulting in bleeding. The blood and the shed endometrium are discharged from the vagina, which is what we call “menstruation”. From a natural physiological point of view, menstruation is the result of a failed conception, a sign that a mature egg has been released by a spermatozoa. However, the ovaries and uterus are strong for the reproduction of the race. Even with repeated failures, the lining of the uterus is always prepared for every possible conception. The follicles in the ovaries also begin to develop and move on to the next menstrual cycle. The cycle gradually becomes more and more regular. Normal menstruation has a certain periodicity. The first day of bleeding is the beginning of the menstrual cycle, and the time interval between the first day of menstruation is called “one menstrual cycle”. The average menstrual cycle is 28 days, but 7 days early or 7 days late is almost always considered normal as long as it is always regular, especially if you can have children. As for the 28 days of the menstrual cycle and the fact that each month of pregnancy is also counted in 28 days as mentioned later, I thought of the lunar calendar, the lunar calendar, the 28 astrological constellations in the sky, and so on. Could we use the ancient Chinese masterpiece on numbers, the I Ching, to study diseases related to menstruation? If we have enough time and accumulation, maybe we can write a book “I Ching and Menstruation”, which will be a best seller. The duration of each menstrual period is called “menstrual period”, usually 3-7 days. The volume of menstruation is the total amount of blood lost during a menstrual period. The normal volume of menstruation is 20 ml to 60 ml, more than 80 ml is excessive. Menstrual blood is dark red in color, and in addition to blood, there are endometrial debris, cervical mucus and shed vaginal epithelial cells. Since menstrual blood contains prostaglandins and substances from the endometrium that promote non-coagulation of blood (fibrinolytic enzymes), menstrual blood usually does not coagulate. However, if the menstrual flow is excessive, blood clots can form. Is menstrual blood dirty? Actually, menstrual blood itself is not dirty, but it is a good nutrient for bacteria or other microorganisms. Therefore, you need to pay attention to hygiene during menstruation to prevent reproductive tract infections. Generally, there are no special symptoms during menstruation, but some women may experience discomfort in the lower abdomen and lumbosacral area or painful contractions of the uterus during menstruation due to pelvic congestion and the action of certain special substances (such as prostaglandins), and may also experience gastrointestinal disorders such as diarrhea or constipation. A few women may also experience headaches and mild neurological instability, such as irritability, irritability, and sadness. If you experience unbearable lower abdominal pain during or around menstruation, you should be alerted to the presence of certain diseases, the most common of which is a disease called endometriosis. For more details, please refer to “Womb Affair (next volume)”, 97th to 100th. Menstruation is a normal physiological phenomenon for women, but women who have just entered puberty may feel uncertain and fearful. Parents, especially mothers, should tell their children about the causes and consequences of this physiological phenomenon at the appropriate time. In addition to refraining from heavy physical labor and strenuous physical activity during menstruation, you should also pay attention to menstrual hygiene and refrain from swimming or taking a tub bath during menstruation. The menstrual period should not be too cold, otherwise it will cause gastrointestinal discomfort and even aggravate dysmenorrhea. Some people think that you can’t wash your hair during menstruation, which may be biased, as long as you pay attention to protection from cold and flu when washing your hair, there should be no problem. A warm tip that is not science. In the animal world, female animals have a special odor when they ovulate, and their vaginal secretions are used to attract and alert males. Menstruation is a physiological phenomenon unique to primates (including humans), and the visual cues of menstruation are more obvious than the olfactory cues of smell. Some literary works have described the superb man who can smell a woman’s scent and determine her menstrual cycle based on her specific body odor. There is no way to prove the authenticity of this, but although the human sense of smell is significantly degraded compared to many animals, we cannot rule out the possibility that there are individuals with a particularly developed sense of smell. So, be aware of the male “animals” around you. If he is always sniffing around with his nose during a certain period of your life, avoid him or ask him to go far away. You could say that in terms of human reproduction, menstruation is the result of failed conception. To be more literate, menstruation is the tears of a sad crying uterus.