in Body Fluids and Circulation (Cardiovascular System, Circulatory system) by

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  • Blood clotting, also called coagulation of blood plugs ruptured vessels to stop bleeding. Clotting is a complicated process. It involves a series of chemical reactions. Blood clot formation and tightening takes less than an hour.
  • When a blood vessel is damaged the clot formation is initiated, as soluble fibrinogen forms an insoluble mesh of fibrin.
  • FIBRINOGEN is an inactive plasma protein, synthesised by the liver. Once activated, it forms a blood clot.
  • Blood clot forms around the platelet plug.
  • Blood clotting helps the body to maintain fluid homeostasis, as severe bleeding is life-threatening. 
  • The four essential components critical to coagulation are: 1. Prothrombin, 2. Thrombin, 3. Fibrinogen, 4. Fibrin

Blood Clot Formation

  • Blood vessels are punctured.
  • Vessels and platelets are stimulated to release prothrombin activator.
  • Conversion of prothrombin (a plasma protein) is activated into thrombin (an enzyme)
  • Thrombin speeds up the conversion of a soluble plasma protein, fibrinogen, into long insoluble threads of a protein called fibrin (forms the threads of the clot)
  • Fibrin fragments join end to end, forming long threads of fibrin.
  • Fibrin threads wind around the platelet plug in the damaged area of the blood vessel, forming an interlocking net of fibers.
  • Since blood flows through the fibrin net, red blood cells get trapped.
  • Thus the mass of fibrin, platelets, and trapped red blood cells squeezed together to make the initial clot, and reduces the flow of blood at the wound site.
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