The Menstrual Cycle is a monthly sequence of changed that prepares the female body for conception and pregnancy. This cycle repeats itself about every 28 days until either conception occurs or the child bearing years end with a menopause at about the age of 50.
Eggs are made and stored in the ovaries of a women. About every 4 weeks an egg, sometimes called as an ovum, matures and moves from the ovaries where it was stored, down a fallopian tube to the womb. This process is under hormonal control.
The lining of the womb is stimulated to produce a thick lining of mucus and blood ready tp receive and feed a fertilized egg. If the ovum is not fertilized, the lining of the womb breaks down and the blood flows from the body through the vagina. This menstrual bleeding or period goes on for several days. when a period starts, the hormonal cycle begins again with the development of another ovum.
If the egg is fertilized, the lining of the womb is retained and develops into a special organ called the placenta. The placenta allows the exchange of Oxygen, food and waste products between the developing baby and its mother.
Harmons are produced by the placenta which suppress the normal hormonal cycle and prevent further ovulation and mensuration during pregnancy.