answered on 5 Jun 2019:
last edited 6 Jun 2019 4:29 am
hmm.. these “solid substances” might be blood clots. Since the tissue that is being ejected by the uterus is rich in blood, sometimes due to how long it takes for the it all to come out, it might end up clotting (due to existing clotting factors in the blood). If you/anyone you know is worried/ concerned, I recommend speaking with a doctor to make sure everything is ok!
A source says ” Your menstrual period starts when hormones trigger your body to start shedding the uterine lining, exposing small blood vessels and causing them to bleed. While this blood is waiting in your uterus to pass through the cervix and vagina during menstruation, your body produces anticoagulants to help break the blood and tissue down so you can pass it more easily. When the blood is moving faster than the anticoagulants can be produced, however, clots can form”