Blood Coagulation
Blood is a fluid connective tissue which is an essential component in the human body. If the body losses this fluid, it may cause life threatening. Through the clotting mechanism, the body defends against loss of blood. In this case, different coagulation factors, vascular mechanisms, thrombocytes, enzymes, prostaglandins and proteins play important role to clot mechanism and finally stop the loss of blood. In the clotting mechanism, the cellular components are thrombocytes, various enzymes, proteins, endothelial cells and ions.
Blood coagulation is also known as thrombogenesis. Blood coagulation or thrombogenesis is a complicated process by which the blood take shape clots to block and afterward rebuild an injury/wound/cut and cut the bleeding. It is a basic piece of hemostasis preventing blood loss from damaged veins. In hemostasis, a damaged vein or blood vessel wall is stopped by a platelets and a fibrin-containing clot to stop the bleeding so that the damage can be refurbished.
Blood coagulation is a complex series of events that requires exacting chemical balances. Thirteen proteins in the blood plasma, called coagulation factors or clotting factors respond in a complex casecade to form fibrin strands which strengthen the platelets plug. The coagulation factors are shown in the following table:
Factor Serial No | Name of Factor |
---|---|
I | Fibrinogen |
II | Prothrombin |
III | Thromboplastin |
IV | Calcium ion |
V | Proaccelerin |
VI | Does not exit |
VII | Proconvertin |
VIII | Antihaemophilic factor A |
IX | Chrismas factor |
X | Antihaemophilic factor B |
XI | Antihaemophilic factor C |
XII | Hagman factor |
XIII | Fibrin stabilizing factor Laki-Lorand factor |
The clotting mechanism can be described in the following 2 stages:
Primary Hemostasis: In this case, a weak platelet plug happens. In the injury site, wall of the blood vessel constricts which helps to reduce the flow of blood. Besides this, platelets plug accumulate to the injury side.
Secondary Hemostasis: In this case, weak platelet plug stabilizes for clotting blood by the formation of fibrin network. Blood clotting occurs in the presence of different substances, known as clotting factors.
Blood Coagulation Process

Image Showing Blood Coagulation Process: Image credit: wikimedia.org
Why blood does not clot inside the vascular system?
Blood does not clot inside the vascular system due to the following reason:
Any lesion/wound/cut of blood vessel influences procoagulant factors of injury site to become active and they immediately exceed the supremacy of anticoagulant factors. Thus begin coagulation.
The clear, pale yellow liquid that separates from the clot in the coagulation of blood is called blood serum. It has the same components of plasma except these clotting factor involved in clotting process like fibrinogen, factors II, V, and VIII.