Why do girls have menstruation, why do girls menstruate

Because girls always chant to the moon, haha!

Otherwise, who do you make so many sanitary napkins to sell to?

Why does the sun rise in the east? Many things exist objectively and can only be understood but not understood.

Menstruation is actually the ovulation phenomenon of the ovaries, girls will periodically discharge eggs after the ovaries mature, there are many follicles on the ovarian wall, when a follicle matures, it will automatically fall off, the process of follicle shedding will rupture some capillaries around the periphery, and some dead cells will be eliminated together, which is why menstruation bleeds.

When a girl reaches puberty, periodic bleeding occurs in the uterus every 28 days or so, which is menstruation. After a normal woman menstruates from puberty, she has a regular menstrual cycle until menopause, except for pregnancy and lactation.

The endometrium is divided into two layers, the surface layer is called the functional layer, and the changes in the menstrual cycle are mainly carried out in this layer, and this layer has to go through a shedding and re-repair every menstrual cycle; The layer close to the muscles is called the basal layer, and after the functional layer is shed during the menstrual cycle, a new functional layer is produced from this layer. The endometrium undergoes a financial change with ovulation of the ovaries. After a girl is born, there are many primordial follicles in the ovaries.

After entering puberty, one follicle generally matures every month. The eggs in the mature follicle are released from the ovaries into the abdominal cavity, which is called ovulation. The day of ovulation is roughly in the middle of the next menstrual period, that is, about 14 days before the next menstrual period.

Before ovulation, the ovaries produce estrogen during follicle development, and the endometrium is affected by estrogen and gradually thickens up to about 2 mm.

At this time, the glands of the endometrium grow, the arteries become thicker and bend, and the connective tissue proliferates. After the follicle ruptures and releases the egg, it shrinks and forms the corpus luteum. In addition to estrogen, the corpus luteum also secretes progesterone.

Under the action of estrogen and progesterone, the endometrium continues to thicken to about 5 mm. At this time, the endometrial glands grow further, the secretions of glandular cells increase, the arteries become more dilated and congested, and the fluid in the connective tissue increases.

Because an egg is released every month, the uterine wall thickens after ovulation, and the pregnancy is prepared. However, it is not possible to get pregnant, so the thickened uterine wall of this month must be withdrawn before the egg is released next month. So there will be bloodshed.

And the learning is not very clear, and it often hurts. It hurts because the uterine wall falls off. Then the remnants of the uterus shedding mixed with the blood and flowed out.