Each menstrual cycle starts with the release of Follicle Stimulating Hormone, (F.S.H) from the pituitary gland, which makes the follicles or immature eggs grow.
As the latter increases in size, estrogen is produced from cells around the egg.
Every month this estrogen makes the uterus lining increase ready for the receipt of the fertilized egg.
If after a series of days nothing is implanted, the lining of the womb starts to disintegrate. The result is what is commonly known as menstruation or a period. What this actually is it includes the unfertilized egg and the now unwanted uterus lining.
Hormonally the menstrual cycle is a process utilizing not only the sex organs but also the brain. The pituitary gland, which is the gland at the very base of the brain, controls the sexual organs, both their function and development. FSH and a luteinizing hormone referred to as LH are the most vital hormones in the pituitary gland.
It is the pituitary gland that knows when the estrogen levels in the blood has reached the correct level and that the ovary is ready to release the egg.
Next comes a surge of LH commanding the ovary to release the egg, commonly known as ovulation. On leaving the ovary, it travels along a fallopian tube, of which there are two until it reaches the uterus.
The corpus luteum which is the cluster of cells that made up the follicle stays in the ovary. It is at this point that if sexual intercourse takes place a pregnancy will result.