First, menstruation is a physiological cycle, which occurs between some fertile female humans and female animals such as female chimpanzees. Spiny mice, cows, mares, camels, sows, ewes, etc. Menstruation also occurs, and some mammals go through estrus cycle. In women of childbearing age and primate females, the endometrium undergoes autonomous thickening, vascular proliferation, gland growth and secretion, endometrial collapse and shedding, accompanied by periodic bleeding changes every other month. This periodic vaginal bleeding or uterine bleeding is called menstruation. Menstrual bleeding is also called menstrual blood.
Second, menstrual components are mainly blood (3/4 arterial blood,14 venous blood), endometrial tissue fragments and various active enzymes and biological factors. Among them, fibrinolytic enzyme makes menstrual blood become liquid without coagulation, and prostaglandin plays a role in contracting uterus. Medically, the reproductive cycle experienced by only primates (including humans) is called menstruation, and the reproductive cycle of other mammals is called estrus cycle. Menstruation is regulated by reproductive hormone system and is the need of biological reproduction. The first menstruation of women is called menarche, and the appearance of menarche indicates that women have entered puberty.
Third, the average age of menarche in women 12 years old. Many factors, such as heredity, diet and health, will advance or postpone menarche. The cessation of menstruation marks that women have entered menopause, also known as menopause. The average age of menopausal women is 5 1 year. Of course, just like menarche, many factors, such as heredity, disease, surgery, medical care and so on, will advance or postpone menopause. It is normal to enter menopause between 40 and 58. Menopause that begins at or before the age of 35 is defined as premature aging.