What is the role of platelets in blood?

• A. To transport oxygen.
• B. To initiate clotting and prevent bleeding by forming a platelet plug and aiding in clot formation.
• C. To fight infection.
• D. To regulate blood sugar.

Answer: (C)

Platelets are small fragments that drive hemostasis, the process that stops bleeding. When a vessel is damaged, platelets quickly adhere to exposed surfaces, become activated, and release signals like ADP and thromboxane A2 to recruit more platelets. They aggregate to form a temporary platelet plug and provide a surface for clotting factors to assemble, helping convert fibrinogen to fibrin to stabilize the clot. This is how bleeding is prevented. While platelets can interact with immune responses, their primary role is not fighting infection—that task belongs to white blood cells. Oxygen transport is performed by red blood cells, and regulation of blood sugar involves other systems and cells.