Answer:
In the follicular phase, the follicles grow inside the ovary. The ovulatory phase is the time of greatest fertility for women. In it, estrogen levels peak just before the egg is released. In the luteal phase, after ovulation the follicular structure that remains in the ovary reorganizes and becomes a gland known as the corpus luteum. The self-determined life of the corpus luteum causes it to degenerate after 14 days and end a menstrual cycle. At the end of the luteal phase, progesterone and estrogen levels drop and menstruation occurs.
Explanation:
The follicular phase is where follicles develop (fluid-filled cavities in the ovary that contain an undeveloped egg) that will eventually house the egg. For the development of follicles, the body sends a signal to the brain to start the production of follicle stimulating hormone (FSH), the follicles begin to develop and produce estrogen. In the ovulatory phase, the level of estrogen in the body continues to rise, causing a rapid rise in LH. This increase causes the secretion of proteolytic enzymes that will degrade the follicular tissue allowing the maturation process of the ovum and its release to finish, a fact known as "ovulation". Ovulation usually occurs between 24 and 36 hours after the LH surge, so luteinizing hormone is a good factor for measuring the period of maximum fertility and knowing the fertile days of the woman. In the luteal phase, the corpus luteum develops that will last until a possible pregnancy or menstruation occurs, starting the next cycle. The egg, after being released, travels through the fallopian tube to the womb. It can survive up to 24 hours and sperm up to 5 days inside the uterus, therefore the days before ovulation and the day of ovulation itself, which can be calculated with the ovulation calendar, are those of maximum fertility and higher chances of pregnancy. After ovulation, the follicle begins to contract but continues to produce progesterone and begins to produce estrogen in order to continue preparing the uterus to receive the embryo.
