Which statement about platelets during hemostasis is correct?

• A. Platelets become macrophages.
• B. Platelets synthesize antibodies.
• C. Platelets cause fibrin to dissolve.
• D. Platelets adhere to damaged site to form a platelet plug.

Answer: (D)

The main idea is how platelets function in hemostasis to form the initial plug at a damaged site. Platelets are recruited to where the vessel wall is broken, adhere to exposed collagen via von Willebrand factor, and become activated. They extend processes, release granules that attract and activate more platelets, and use receptors like GPIIb/IIIa to bind fibrinogen and link platelets together. This creates a temporary platelet plug—the first step in stopping bleeding, known as primary hemostasis. This mechanism explains why the statement about platelets adhering to the damaged site to form a platelet plug is correct.

Platelets do not become macrophages, which are derived from monocytes, and they do not synthesize antibodies, which are produced by B cells/plasma cells. They also do not dissolve fibrin; fibrinolysis dissolves the clot later, mainly via plasmin activated by tissue plasminogen activator. The platelet plug is then reinforced by the coagulation cascade forming a fibrin mesh, stabilizing the clot.