- 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)
Image source: wikipedia
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