Menstruation is caused by the regular shedding of the endometrium once a month. This is by no means an active behavior of the uterus, but a passive behavior controlled by another organ. This organ is the ovary. One follicle matures in the ovary and one egg is released every month. This is the real driving force behind the cyclic changes in the endometrium. In other words, the menstrual cycle is based on the cycle of follicle development.
A complete menstrual cycle is completely controlled by follicle development. When menstruation begins, one or several follicles develop in the ovaries. As the follicles grow larger, estrogen levels continue to increase. Under the action of estrogen, the cells in the basal layer of the endometrium proliferate, repair the wounds after the endometrium peels off, and menstruation stops; later, the endometrium continues to proliferate and become thicker, and the number of glands increases. At this time, the endometrium is in the proliferative phase. When the follicle develops to about 20 mm and matures, estrogen will suddenly rise very high, triggering a pulse of another hormone LH (luteinizing hormone), so the follicle ruptures, the egg is expelled, and the remaining follicle transforms into the corpus luteum. The corpus luteum produces a large amount of progesterone and estrogen. Under the influence of progesterone, the endometrium continues to thicken, the glands further enlarge, bend, and secrete. At this time, the endometrium is in the secretory phase.
The so-called proliferative phase and secretory phase are morphological differences in the endometrial tissue. Doctors can judge whether the ovary has ovulated based on the state of the endometrium. The endometrial proliferation phase is entirely caused by estrogen produced by follicle development, so it is also called the follicular phase; while the secretory phase is caused by progesterone produced by the corpus luteum, so this period is called the luteal phase.
So, the entire menstrual cycle is divided by the rupture of follicles and the discharge of eggs, forming two different intervals before and after. Since it takes 14 days for primary follicles to develop into mature follicles, and the life span of the normal corpus luteum is also 14 days, the standard menstrual cycle is 28 days, but only 15% of women have a typical menstrual cycle of 28 days. The follicular development of most other women is either fast or slow, but as long as the menstrual cycle is within plus or minus 7 days of 28 days, that is, the menstrual cycle of 21 to 35 days is considered normal. What needs to be emphasized is that the difference in the length of the menstrual cycle depends entirely on the speed of follicular development. If the follicles develop slowly, the follicular phase will be very long; if the follicles develop quickly, the follicular phase will be shortened, and the lifespan of the corpus luteum is not It varies, it is about 14 days (maximum error is 2 days).
This article is provided by Baidu Reading and is excerpted from \”Pregnancy Can Be Simple\” Author: Feifei Mom