The first day of the menstrual cycle is the first day of menstruation. Menstruation occurs because no fertilized egg implanted in the uterus during the previous cycle. The body secretes two hormones – estradiol (estrogen) and progesterone – to prepare the fertilized egg for implantation in the uterus. Unavailable, their levels plummet, causing the thickened, blood-rich layer of the uterine lining to shed, which is called menstrual bleeding.
After the menstrual period begins, the pituitary gland begins to secrete follicle-stimulating hormone again to stimulate follicle expansion. It is still unknown why certain follicles in a woman (almost always one) respond to increasing stimulation of follicle-stimulating hormone. However, under the stimulation of follicle-stimulating hormone, some follicles in most women will increase in size, and one of the follicles almost always secretes more estrogen than the other follicles, eventually becoming the dominant follicle during the cycle. One egg is released on day 14. When follicle-stimulating hormone appears, these follicles will also secrete estradiol. Estradiol enters the person\’s bloodstream and brain, resets the person\’s hypothalamus and pituitary gland, and re-adjusts the follicle-stimulating hormone and corpus luteum in the next few days. Generates hormone secretion.
The enlargement of follicles, the maturation of eggs and their discharge are processes in which hormone levels in the body are constantly changing. A prerequisite for ovulation is that reproductive hormones reach appropriate levels in the blood at the appropriate time.
At 8 to 10 days, the rapidly increasing dominant follicles can be clearly seen through ultrasound. Although the egg itself is too small to be seen with the naked eye, it matures within the follicle and becomes fertilized. In the cellular state, an egg contains all the chromosomes that a normal cell has. The egg continues to develop naturally until it is stimulated by a large increase in luteinizing hormone during the mid-cycle. Under the stimulation of luteinizing hormone, one pair of chromosomes detaches from the cell body and forms a polar body outside the cell wall. Cell polar bodies, composed of residual chromosomes, are used by infertility laboratories as a marker to determine whether an egg is mature during in vitro fertilization.
By 12 to 13 days, the size of the dominant egg reaches its maximum, and the secretion of estrogen also reaches its maximum, causing the pituitary gland to become sensitive to gonadotropin-releasing hormone. In response, the pituitary gland begins to release stored luteinizing hormone. The timely surge of luteinizing hormone, coupled with the frequent interaction of other hormones within the follicle, controls the growth and development of the egg and final ovulation. After the growth of luteinizing hormone reaches the required value of the follicle, the follicle ruptures within 24 to 36 hours, and the fluid leaks out together with the egg. This is the process of ovulation.
After ovulation is completed, the empty follicle turns into a yellowish sac-like body called the corpus luteum. During phase 2 of the ovulation cycle, the corpus luteum continues to produce estrogen and secretes progesterone.
This article is provided by Baidu Reading and is excerpted from \”The Clear \”Conception\” Plan\” Author: Sun Jianqiu and Xie Yingbiao