Women get their periods regularly every month. The bleeding that you see on your pad or tampon or in the toilet bowl is a mixture of both blood and tissue from the lining of your uterus.
The amount of period blood, along with other factors, will influence what your period blood looks like.
What Causes Bleeding?
When the hormone changes cause the uterine lining from the wall of your uterus, your period starts. This lining has built up during the earlier weeks of your cycle.
Your menstrual flow is a mixture of this built up tissue combined with blood loss from the blood vessels from the wall of the uterus.
A cut on your finger will bleed until clotting factors are released that stop the bleeding. Similarly, blood will flow from the small blood vessels that were torn when the lining of the uterus separated.
This bleeding will continue until clotting factors and hormone changes stop the bleeding and restart building up the uterine lining again. This is called the menstrual cycle.