What is the term for the aggregation of platelets at the site of vascular injury?

The aggregation of platelets at the site of vascular injury is known as primary hemostasis. This is the initial response to vascular damage, where platelets rapidly adhere to the exposed subendothelial structures via specific receptors and, upon activation, release various substances that enhance aggregation and attract more platelets to the site. This process is crucial for forming a temporary plug that helps to seal small breaches in the vascular system and prevents excessive bleeding.

In the context of hemostasis, this phase is clearly distinct from secondary hemostasis, which involves the complex cascade of coagulation factors leading to the formation of a stable fibrin clot. While coagulation is critical for effective hemostatic function, it follows the initial platelet aggregation and is often referred to as secondary hemostasis.

Fibrinolysis, on the other hand, is the process by which the fibrin clot is dissolved after the vascular integrity is restored, completely separate from the aggregation phase that defines primary hemostasis. Understanding these phases helps clarify the sequential events in the overall hemostatic process following injury to the blood vessel.