Blood clots are not a normal condition, but they occur when blood coagulates or hardens. They typically form after the body is injured to prevent excessive bleeding. Also called a thrombus, it is made when blood cells lump together with fibrin, a stretchy, thread-like protein. Research has shown fibrin to be a strong material that can absorb blood from cuts to help heal them, but is also responsible for making blood clots hard to break down. Medications are now available to help destroy clots by working to break up the fibrin.
In the bloodstream, clots that develop and remain in the heart or in a blood vessel are called thrombi. Emboli are those that are located somewhere in the body besides the heart or a blood vessel, and they create an embolism. A thromboembolism occurs when a part of the thrombus causes a blockage to the heart, brain, or lungs and stops or restricts blood flow. When this happens, it could cause a heart attack or stroke.
Blood clots can also destroy body tissues because, as the blood flow is restricted, oxygen is kept out of the tissues in that part of the body. Ischemia is the name of the condition that occurs when no blood flow or oxygen reaches the tissue. If ischemia is left unchecked, body tissues in the affected region can be damaged or die.
Deep venous thrombosis (DVT) is a condition in which blood clot develops in a vein in the lower part of the body, such as the pelvis, thighs, or lower legs. This can seriously restrict the blood flow in the limb and may cause swelling and redness, although some people do not experience any systems. Other people experience a lot of pain when blood clots form. Genetic factors are thought to be partly responsible for the causes of deep venous thrombosis, although poor circulation caused by sitting in long airplane flights is thought to be another causative factor in some cases. If the clot breaks free and travels to the lungs or heart, it can be fatal.