UPSC 2013 CDS 2 GK Paper

Blood does not coagulate inside the body due to the presence ofHeparin. Heparin is a naturally occurring anticoagulant releasedfrom mast cells that prevents blood from clotting inside vessels. Blood clots are clumps that occur when blood hardens from liquid to solid. A blood clot that forms inside our veins or arteries is called a thrombus.