Answer:
If the egg cell is not fertilized, it dies. At the end of the cycle some blood vessels in the mucous membranes of the uterus open up for some time, and the uppermost mucous layer detaches.
If the egg cell is not fertilized, it dies. At the end of the cycle some blood vessels in the mucous membranes of the uterus open up for some time, and the uppermost mucous layer detaches. In order to discharge it, the muscles in the uterus contract and then relax again in an irregular rhythm.
