How does menstruation occur?

Women usually start to have menstruation at the age of 12 or 13. The first menstrual period is called menarche. At that time, the ovarian function of women is not stable, so menstruation is irregular. After menarche, it usually takes several months, half a year or longer for menstruation to come again. Generally, women will gradually form a regular period about 2 years after menarche.

So, how does menstruation occur?

When a girl enters puberty, her ovaries begin to ovulate, and at this time, the ovaries can produce two hormones, namely estrogen and progesterone. These two hormones can thicken the endometrium of the uterus. If the egg is not fertilized after being released, the corpus luteum will slowly shrink, causing a sharp decrease in the secretion of these two hormones. The thickened endometrium will not receive hormonal support, and will undergo degenerative changes and ischemic necrosis, and fall off, and flow out of the body through the vagina to form menstruation. It can be seen that menstrual blood is a mixture of shed endometrium and a small amount of blood. It can be said that menstruation plays a cleaning role in the shedding of the endometrium.