The menstrual cycle begins on the first day of a woman’s period. It comprises two phases: an initial "ollicular" phase, which lasts for approximately 14 days, and a second "luteal" phase of the same duration.
At the start of the follicular phase, a follicle
containing an ovule develops in an ovary under the influence of certain hormones known as gonadotrophins
(LH et FSH).
Around the 14th
jour, when this follicle reaches a diameter of approximately 2 cm, it releases the ovule it contains. This is known as ovulation.
The follicular phase ends at this point and the luteal phase begins. After ovulation, the tip of the fallopian tube comprising tens of fimbriae (fringes), will seize the ovule for subsequent transportation along the fallopian tube.
If intercourse takes place, approximately 50 to 300'000 spermatozoa
are ejaculated and will cover a long distance (approximately 15 cm). They will migrate towards the fallopian tubes via the Cervix uteri
. The spermatozoa meets the ovule in the fallopian tube. At this point, the genes of the father and the mother merge to create a new human life. The embryo thus created will divide and continue its migration along the fallopian tube
towards the uterus where it will become implanted if the environment is conducive. This heralds the start of pregnancy.
After ovulation, the follicle that released the ovule transforms into the Corpus luteum. In the event of pregnancy, the Corpus luteum persists, the placenta forms and triggers hormone production. Otherwise the Corpus luteum disintegrates and the period will begin.