QS Study

Role of Platelet in Haemostasis

Platelets are a component of blood whose function is to stop bleeding by clumping and clotting blood vessel injuries. Platelets are small anucleate cells generated from megakaryocytes in the bone marrow. Hemostatic balance is central to health maintenance. Hemostasis must be initiated rapidly to prevent excessive blood loss.

Fig: Role of Platelet in Haemostasis

(1) Haemostatic function

It helps in the haemostasis in the following ways—

  • Vasoconstriction: It liberates 5HT which is a vasoconstrictor.
  • Formation of platelet plug: It secretes platelet thromboplastin, phospholipid, ADP which help in the formation of prothrombin activator and coagulation.
  • Clot retraction: Thromboplastin of platelet in presence of ADP and Mg2+ helps in clot retraction.

(2) Initiate blood clotting

When blood as a shed, the platelet disintegrates and liberates thromboplastin which activates prothrombin into thrombin.

(3) Repair capillary endothelium

While in circulation, the platelets adhere to the damaged endothelial lining of the capillaries and thus bring about speedy repair.

(4) Helps defensive mechanism

Due to their increased agglutinating tendencies, they encircle the foreign bodies, thus aids in the defense activities of the body.