Why do girls have their periods?

When it comes to the question of why women have menstruation, perhaps most people think it is normal, because women will have periods, and they will continue until menopause. During menstruation, they may also encounter various problems such as dysmenorrhea and dizziness. The menstrual period is indeed very difficult to endure, and they are also afraid of side leakage. Therefore, many women do not like periods. So why do women have periods?

1. What is menstruation?

The main components of menstruation are blood, endometrial tissue fragments and various active enzymes and biological factors. Among them, fibrinolytic enzyme makes menstrual blood liquid and prevents it from coagulating, and prostaglandins play the role of contracting the uterus. Medically speaking, only the reproductive cycle experienced by primates (including humans) is called menstruation. In addition, the reproductive cycle of other mammals is called the estrus cycle. Menstruation is regulated by the reproductive hormone system and is necessary for biological reproduction. A woman's first menstruation is called menarche, and the onset of menarche marks the entry of a woman into puberty. The average age of menarche for girls is 12 years old. Many factors, including genetics, diet, and physical health, can cause menarche to come earlier or later. The cessation of menstruation marks that a woman has entered menopause, also known as menopause. The average age of menopausal women is 51 years old. Of course, just like menarche, many factors such as genetics, disease, surgery and medical treatment can advance or delay menopause. It is normal to enter menopause between the ages of 40 and 58. Menopause occurring before the age of 35 is defined as premature aging.

2. 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 follicle 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 21-30 days, but varies from person to person, and may 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 3-7 days, and the total amount of bleeding each time is 30-50ml. Some people believe that menstrual volume exceeding 80ml is a pathological condition.