In the described clotting process, what step occurs immediately after the vessel wall contracts?

In the described clotting process, what step occurs immediately after the vessel wall contracts?

• A. Platelets adhere to endothelium
• B. Platelets become sticky to other platelets
• C. Platelets fill hole
• D. Prothrombin activator catalyzes conversion of prothrombin to thrombin

Answer: (A)

When a vessel is damaged, the first local response is to reduce blood flow through vasoconstriction. Right after that, platelets latch onto the exposed damaged surface. This adhesion is driven by von Willebrand factor, which binds to exposed collagen and to platelet receptors, anchoring platelets to the injured endothelium. This initial sticking forms the scaffold for a platelet plug. Once adhered, the platelets become activated and stickier, recruiting more platelets to reinforce the plug, which is the next step before the coagulation cascade kicks in to stabilize the clot with fibrin.

When a vessel is damaged, the first local response is to reduce blood flow through vasoconstriction. Right after that, platelets latch onto the exposed damaged surface. This adhesion is driven by von Willebrand factor, which binds to exposed collagen and to platelet receptors, anchoring platelets to the injured endothelium. This initial sticking forms the scaffold for a platelet plug. Once adhered, the platelets become activated and stickier, recruiting more platelets to reinforce the plug, which is the next step before the coagulation cascade kicks in to stabilize the clot with fibrin.