Answer:
A. Menstruation and the estrogen surge
Explanation:
The events that occur simultaneously in the monthly female reproductive cycle are menstruation and estrogen increase.
The menstrual cycle lasts about 28 days and is controlled by the secretion of gonadotropins (FSH and LH), secreted by the pituitary, and estrogen and progesterone, produced by the ovaries. The first day of the cycle corresponds to the first day of menstruation. During menstruation, levels of sex hormones in the blood are low. By the sixth day, the pituitary again secretes a greater amount of follicle stimulating hormone (FSH).
Therefore, in this first phase of menstruation, the pituitary secretes the hormone FSH, which, as the name implies, will stimulate the development of ovarian follicles. In turn, the follicles produce estrogen, which stimulates the growth of cells in the uterine inner wall, the endometrium, which becomes thicker and well-vascularized. These are changes that prepare the uterus for the implantation of an embryo, ie a pregnancy.
The high concentration of estrogen in the blood stimulates the secretion of luteinizing hormone (LH). LH induces ovulation, which occurs around the 14th day of the cycle. Next, the LH induces the rupture of the ovarian follicle and the consequent release of the egg, besides leading to the development of the corpus luteum. The corpus luteum produces progesterone, which will assist in maintaining the endometrium until the end of the menstrual cycle.
