A blood clot a.k.a. as thrombus is the result of a reactions involving various proteins, their activators, and inhibitors. Thrombosis of a vein is a clot made up of red blood cells, white blood cells and platelets. The clot sticks to the lining of the vein and may partially or totally block the blood.
Thrombosis is the basis of a number of disorders.
Clots can develop anywhere in the the body, and can involve the organs. If clotting occurs in the surface veins, it is usually not dangerous and often heals on its own. If both the surface and deep veins are involved, it may be dangerous. Heart attacks and strokes are very often due to thrombosis. The morbidity and mortality associated with clot formation is staggering.