An Introduction to the Fundamentals of Coagulation: Introduction to Primary Hemostasis

Primary Hemostasis – The Vascular System & Platelet Involvement

  • As discussed earlier, a break in the vessel endothelium leads to exposure of collagen and the vessel's subendothelial surface.
  • Ruptured endothelial cells leak ADP and Serotonin, which are the chemical triggers that induce platelet adhesion, the next step in the sequence of hemostatic events.
  • Circulating platelets are drawn to the area by those liberated chemical signals, and begin to physically attach themselves to the rough, damaged surfaces of the breach.
  • As platelets continue to arrive and bind to the exposed collagen and basement membrane, a rudimentary barrier begins to form, as the platelets themselves serve to fill in the breached vessel wall.
  • Platelets possess an inherent “sticky” property which enables them to adhere to one another, and not just to the damaged vessel endothelium.
  • The process by which platelets bind to one another is referred to as platelet aggregation, and is vital because it allows for a platelet plug to be formed.
  • The platelet plug is the structure responsible for plugging the hole in the vessel wall.








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