Mechanism of blood coagulation

  • The blood clots or coagulates within 2-6 minutes if it gets collected in a tube.
  • It changes into semisolid jelly. This phenomenon is called coagulation or clotting.
  • When skin or any other body part is cut, the blood flows out.
  • But it quickly clots and thus stops the blood oozing out.
  • It is called blood clotting. The normal clotting time is about 2-6 minutes.
  • Blood coagulation is a very complicated process and is under a sensitive control.
  • The capacity of blood to clot is essential to life.
  • Hemorrhage occurs in absence of this self-sealing function.
  • For blood clotting, blood platelets are responsible which takes place in many stages. They are :

i)Release of thromboplastin

  • At the site of injury, thrombocytes come outside.
  • When get exposed to air, they become damaged which after releases thromboplastin.

ii)Formation of thrombin

  • Thromboplastin together with many clotting factors and calcium ions Ca++ acts on the plasma protein prothrombin and thus converts the prothrombin into active thrombin.
  • It is a proteolytic enzyme.

Prothrombin + Ca++  (thromboplastin)  →  Active thrombin (in plasma)


Coagulation - Wikipedia

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iii)Formation of fibrin

  • Thrombin acts on the soluble plasma protein fibrinogen and converts it into insoluble fibrin.
  • Fibrinogen   ( thrombin )    ⟶     fibrin

iv)Formation of blood clot

  • The forms a network of fibre in which RBCs and WBCs are trapped to form a red solid mass called blood clot. 

Fibrin polymer  ( fibrin ) ⟶   insoluble fibrin clot





Mechanism of blood coagulation