Adhesion of platelet to collagen is due to
**Core Concept**
The adhesion of platelets to collagen is a critical step in the formation of a hemostatic plug during bleeding. This process involves the interaction between platelets and the extracellular matrix, specifically collagen fibers. The adhesion is mediated by specific receptors on the platelet surface that bind to collagen molecules.
**Why the Correct Answer is Right**
The correct answer is **von Willebrand factor (VWF)**. VWF is a large, multimeric protein that plays a key role in platelet adhesion to collagen. It binds to both platelet glycoprotein Ib and collagen fibers, facilitating the formation of a platelet-collagen bridge. This bridge is essential for the recruitment of additional platelets and the stabilization of the hemostatic plug.
**Why Each Wrong Option is Incorrect**
* **Option A:** Glycoprotein IIb/IIIa is a receptor on platelets that binds to fibrinogen and other ligands, but it is not directly involved in the adhesion of platelets to collagen.
* **Option B:** Fibrinogen is a key protein in the coagulation cascade, but it is not the primary mediator of platelet adhesion to collagen.
* **Option D:** None of the other options provided are correct. This distractor serves as a reminder to carefully evaluate each option and not default to an incorrect choice.
**Clinical Pearl / High-Yield Fact**
Von Willebrand disease is a common bleeding disorder caused by defects in VWF. Patients with this condition may exhibit mucocutaneous bleeding, such as nosebleeds or easy bruising, and may have a prolonged bleeding time.
**Correct Answer:** C. von Willebrand factor (VWF)