#139 Menstrual cycle
The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for pregnancy, and if pregnancy does not happen, the lining is shed at menstruation. The cycle lasts about 28 days.
Several hormones control this cycle:
- Usually, one egg is released from an ovary every month. Before the egg is released, the lining of the uterus becomes thick and spongy to prepares for a fertilised egg. It is full of tiny blood vessels, ready to supply the embryo with food and oxygen if it should arrive.
- If the egg is not fertilised, it is dead by the time it reaches the uterus.
- Is does not sink into the spongy wall, but continues onwards, down through the vagina.
- As the spongy lining is not needed now ---> it gradually disintegrates and is slowly lost through the vagina.
- This is called menstruation, or period and it last for about 5 days.