Are platelets required for blood clotting?

[sameeralord]

In blood clotting disorders, clotting time is increased, but when there is plalete disorder clotting time is not affected. What is the reason for that. Aren't platelets required for blood clotting. Also when a fibrous mesh is formed, do red blood cells and platelets get stuck in it. Is it why blood clots. Thanks

 

[SW VandeCarr]

In blood clotting disorders, clotting time is increased, but when there is plalete disorder clotting time is not affected. What is the reason for that. Aren't platelets required for blood clotting. Also when a fibrous mesh is formed, do red blood cells and platelets get stuck in it. Is it why blood clots. Thanks

Platelets are activated in primary hemostasis to form an initial plug which becomes enmeshed in the fibrin clot as the coagulation cascade proceeds (secondary hemostasis). Platelet activation is initiated with the release of von Willibrand factor from damaged vessel walls.

Prothrombin time (INR) measures only the extrinsic coagulation pathway in vitro and is only meaningful relative to a standard control time. Both primary and secondary hemostasis are necessary to form a stable clot as far as I know.