Menstrual cycle from 28 days to 21 days

Generally speaking, a normal menstrual period is 28 days, but sometimes, if a woman is under a lot of stress in life or is in a bad mood, the cycle will change. A menstrual cycle that changes from 28 days to 21 days is a common and normal physiological condition. However, if it is accompanied by other pains, excessive or insufficient menstrual flow, then you need to go to the hospital for a check-up.

After women enter puberty, the endometrium is affected by ovarian hormones, causing periodic uterine bleeding, which is called menstruation. The cyclical changes in the endometrium are called the menstrual cycle, which is also the human reproductive cycle.

The period from the first day of menstruation to the day before the next menstruation is usually called a menstrual cycle, and each menstrual cycle lasts an average of about 28 days. According to the histological changes of the endometrium, the menstrual cycle is divided into three phases:

(1) Proliferative phase (preovulatory and follicular phases). Equivalent to the 5th to 14th day of the menstrual cycle. The follicles secrete female hormones, which gradually repair and thicken the endometrium, cause blood vessels and glands to proliferate, and allow the follicles to develop until they mature and ovulate.

(2) Secretory phase: From ovulation to the next menstruation, that is, the 15th to 28th day of the menstrual cycle. The corpus luteum grows and matures, and secretes large amounts of progesterone and estrogen. Under the action of hormones, the endometrium and glands continue to grow and secrete mucus, preparing conditions for the implantation and development of the fertilized egg.

(3) Menstrual period. If the egg cell is not fertilized, the corpus luteum gradually shrinks, hormone secretion decreases sharply, and the endometrial blood vessels spasm, causing the endometrium to become ischemic, necrotic and detached. Blood vessels rupture and bleed, and blood and detached endometrial fragments are discharged through the vagina. It lasts about 3 to 5 days, and the amount of bleeding varies from 50 to 100 ml. Generally, girls begin to have their first menstruation at the age of 13 to 14, which is called menarche. The menstrual period ends at 45 to 50 years old. The human nervous system regulates ovarian activity, and mental stress or excessive anxiety can cause menstrual cycle disorders. There is usually no menstruation during pregnancy and breastfeeding.