Blood clot Blood clot Blood clot Blood clot Blood clot is a jelly-like mass of congealed blood. Clotting is the normal way the body stops bleeding and begins healing, following injury. It involves complex chemical reactions between many substances that are present in the blood plasma. Absence of one of these substances results in the disorder hemophilia. A clot within a blood vessel is called a thrombus.
Cerebral thrombosis is a blood clot in an artery to the brain, which can cause a stroke.
Blood clotting also occurs more easily if the circulation is slow, a condition in individuals with varicose veins. Other factors that increase the likelihood of blood clots are major injury to the body, the prolonged use of such drugs as birth control pills, smoking, and prolonged bed rest.