How many days is a normal menstrual cycle for women

After women enter puberty, the uterine wall is affected by the uterine and ovarian hormones, and regular uterine bleeding occurs, which is called menstruation. The regular changes in the uterine wall are called the physiological cycle, which is also the human reproductive cycle.

Menstrual cycle installments and related histological changes

Generally, the first day of menstruation to the day before the next menstruation is called a menstrual cycle, and each menstrual cycle is about 28 days on average. According to the histological changes of the uterine wall, the physiological cycle is divided into three stages: (1) proliferative phase (early ovulation phase, follicular phase). Equivalent to days 5 to 14 of the menstrual cycle. The egg metabolizes estrogen, causing the uterine wall to slowly repair and thicken, blood vessels and glandular ducts to proliferate, and the uterus to develop until the ovulation period is complete. (2) Metabolic stage. From the ovulation period to the next menstrual period, that is, the 15th to 28th day of the menstrual cycle. The corpus luteum grows and develops fully, and metabolizes a lot of estrogen and estrogens. Under the action of hormones, the uterine wall and glandular ducts continue to grow and secrete mucus, preparing the conditions for the implantation and development of the sperm and egg combination. (3) Menstrual period. If the egg is not fertilized, the corpus luteum will slowly shrink, the metabolism of growth hormone will be greatly reduced, and the blood vessels in the uterine wall will spasm, causing the uterine wall to become ischemic and necrotic and detach. Blood vessels rupture and bleed, and the blood and fallen endometrial fragments are discharged through the vagina. It lasts about 3 to 5 days, with the amount of bleeding varying from 50 to 100 ml. Generally, women begin to have their first menstruation at the age of 13 to 14, which is called the first menstruation. The menstrual period stops between 45 and 50 years old. The human central nervous system has a buffering effect on uterine and ovarian activity, which can lead to disruptions in the physiological cycle when one is nervous, anxious, or overly anxious. There is generally no menstrual period during pregnancy and breastfeeding.

Physiological mechanism of menstrual cycle

The time interval between the first days of 2 menstrual periods. Most of them are within 28 to 30 days, and 7 days earlier or later is within the normal range. The length of the cycle varies from person to person, but every woman's menstrual cycle must have her own periodicity, otherwise it should be considered abnormal. The menstrual cycle is regulated by the interaction between the hypothalamus-pituitary gland-pituitary gland-uterus and ovaries. The hypothalamus regulates the action of the pituitary gland, which in turn regulates the function of the ovaries. The uterine wall undergoes regular changes under the action of uterine and ovarian hormones. The estrogen produced by the uterus and ovaries acts on the hypothalamus and pituitary gland, affecting the release of gonadotropin-releasing hormone (Gn-RH), follicle-stimulating hormone (FSH) and luteinizing hormone converted into growth hormone (LH), which is a feedback effect. Inhibiting its release is also called negative feedback, and promoting its release is also called feedback regulation.

After the first menstrual cycle, the secretion of lutein and estrogen decreases, eliminating the inhibition of the hypothalamus and pituitary gland. Gn-RH produced by the hypothalamus-pituitary gland promotes the metabolism and release of FSH and LH. Under the synergistic effect of FSH and LH, the eggs in the ovaries of the uterus gradually grow and mature, and the estrogen produced causes the uterine wall to undergo a proliferative phase. After the egg is formed, the body's estrogen levels peak for the first time. The secretion of female hormones increases, inhibiting the production of FSH, promoting the increase of LH metabolism, causing the LH peak and starting the ovulation period. After ovulation, progesterone is produced, which metabolizes estrogen and estradiol. Under their interaction, the uterine wall undergoes typical metabolic changes. After ovulation, estrogen levels temporarily decrease, followed by a second, lower peak. The large amount of estrogen and estrogens secreted by progesterone, through the negative feedback effect, reduce the secretion of FSH and LH, and the progesterone begins to shrink. Later, as female hormones and estrogen metabolism decrease, the uterine wall cannot be supplied by estrogen, causing necrosis and shedding, leading to the onset of menstruation. After the corpus luteum shrinks, it eliminates the inhibition on the hypothalamus and pituitary gland, and Gn-RH is metabolized again to start another physiological cycle.