Ovulation
4. What happens before and after ovulation?
The menstrual cycle consists of two phases, before and after ovulation, during which anatomical and physiological changes take place in the ovarian follicles containing the eggs, the uterine lining and the mucus secreted from the cervix (mucus cervical). These events are repeated monthly to allow fertilization, implantation of an egg cell, or removal of the lining of the uterus if there has not been a pregnancy.
The follicular or pre-ovulatory phase (1st to 14th day)
The follicular phase begins with the elimination of the uterine lining which gives rise to menstruation, i.e. the discharge from the vagina of a mixture of blood, cells of the uterine lining, bacteria and mucus cervical. They last from 2 to 7 days depending on the woman, 5 days on average.
A phase of selection and maturation follows in the ovary of a follicle containing an oocyte for the next 7 days. This phenomenon is dependent on the follicle-stimulating hormone FSH, secreted by the pituitary gland, a small gland located under the brain. Initially, several follicles begin to grow but only one of them completes its maturation, this is the dominant follicle. The others will be eliminated.
During this phase, the ovaries secrete estrogen. This will have two consequences. Cervical mucus, mucus secreted by the cervix becomes more fluid, translucent, watery, alkaline a few days before ovulation. This phenomenon makes it easier for sperm to pass into the uterus if there is sexual intercourse. But these hormones also work in the uterus, causing the uterine wall to thicken to accommodate a possibly fertilized egg.
At the end of this phase, ovulation occurs: the follicle ruptures on the surface of one of the two ovaries and releases an egg into the fallopian tube. It is triggered by the profuse secretion of another hormone produced by the pituitary gland, LH (luteinizing hormone). This phenomenon occurs 14 days before the date of the next period. The egg will be picked up by the tube and can be fertilized there by a sperm, if the couple has had one or more sexual intercourse within the previous 48 to 72 hours. The egg will only be fertile for a dozen hours.
All this happens from the 1st to the 14th day on average. However, the process can take longer or shorter since every woman is different.
The luteal or post-ovulatory phase (14th to 28th day)
It usually lasts about 13 to 15 days from ovulation until the first day of your period.
The part of the follicle that remains attached to the ovary after its oocyte is expelled, called the corpus luteum, produces progesterone which works with estrogen to keep the lining of the uterus thick and ready to receive the fertilized egg. Progesterone helps the development of glands and vessels.
If a pregnancy starts, the egg cell that is nesting in the uterus sends hormonal signals to the ovaries to maintain the secretion of hormones and a thickened, blood-filled endometrium. In the absence of fertilization, the corpus luteum regresses, production of progesterone and estrogen collapses, and the endometrium begins to break down, leading to menstruation and the start of a new cycle.
During this period, cervical mucus is thick and forms a tight mesh at the entrance to the cervix, largely preventing the passage of sperm.
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