Why do we have menstruation?

When a woman reaches puberty, she will experience her first menstruation. When a girl has her first menstruation, if she does not have the relevant knowledge and experience before, she will be very scared. Some girls will be scared by their first menstruation. From this time on, she will have her menstruation every month. This is a phenomenon that every woman will encounter. Girls must learn how to protect themselves during menstruation. So what causes women to have their periods?

Why do we have menstruation?

In order to explain this issue, we must first understand the structure and physiological functions of female reproductive organs.

The female internal reproductive organs consist of the ovaries, uterus, and fallopian tubes. The main function of the ovaries is to produce eggs and synthesize ovarian hormones, while the uterus and fallopian tubes are reproductive organs. The ovaries contain hundreds of thousands of follicles, each of which contains one egg.

Before puberty, the follicles are essentially non-functional. During puberty, under the action of gonadotropin from the anterior pituitary gland, immature follicles gradually develop and synthesize estrogen. When the follicle matures and ovulates, the ovarian wall collapses, the cells become larger and yellower, and are called the corpus luteum. It synthesizes estrogen and produces progesterone.

As the ovaries change, the endometrium is also affected and undergoes corresponding cyclical changes. Estrogen causes the endometrium to thicken, the endometrial cells to increase in number and size, and the arterioles in the interstitium to become more tortuous and spiral, which is called the proliferative endometrium. After ovulation, due to the combined effects of estrogen and progesterone, the endometrium becomes edematous, the glands produce a large amount of mucus and glycogen, and the thickness of the endometrium increases from 1 mm to 6 mm, which is called the secretory endometrium.

If the egg released at this time is fertilized, the fertilized egg is transported to the uterus through the fallopian tube for development, which is called pregnancy. The pregnancy tissue synthesizes a chorionic gonadotropin, which supports the continued development of the corpus luteum of the ovary. If the egg is not fertilized, the corpus luteum will atrophy and stop secreting estrogen and progesterone about 14 days after ovulation. At this time, the blood vessels in the endometrium contract, the endometrium necrotizes and falls off, causing bleeding and forming menstruation.

Therefore, the length of the menstrual cycle depends on the length of the ovarian cycle, which is generally 28-30 days[1], but varies from person to person and can be 23-45 days, or even 3 months or half a year as a cycle. As long as it is regular, it is generally considered normal menstruation.

The bleeding time is generally 2-7 days, and the total amount of bleeding each time is 30-50ml. Some people believe that menstrual volume exceeding 80ml is a pathological condition.