Von Willebrand factor (vWF) serves two main functions in hemostasis. Which of the following correctly describes BOTH functions?

• A Mediating platelet adhesion to subendothelial collagen AND acting as a carrier protein for Factor VIII ✓
• B Activating the extrinsic coagulation pathway AND inhibiting thrombin
• C Crosslinking fibrin polymers AND activating plasminogen to plasmin
• D Activating platelets via PAR-1 receptors AND providing a scaffold for the prothrombinase complex

Explanation

vWF performs two critical hemostatic functions: (1) Platelet adhesion — vWF bridges subendothelial collagen (via its A3 domain) to platelet GPIb-IX-V receptor (via its A1 domain), especially under high shear; (2) Carrier protein — vWF non-covalently binds and stabilizes Factor VIII in plasma, protecting it from premature proteolysis. Deficiency of vWF (von Willebrand disease) therefore causes both platelet-type bleeding (prolonged bleeding time) and a secondarily low Factor VIII (prolonged aPTT). Fibrin crosslinking is done by Factor XIIIa; thrombin inhibition is done by antithrombin.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.