What is the role of platelets in hemostasis?

• A. They transport oxygen.
• B. They fight infection.
• C. They dissolve clots.
• D. They form the platelet plug and help in clot formation.

Answer: (D)

Platelets are essential for stopping bleeding by both forming a quick plug and supporting the clot-building process. When a blood vessel is injured, platelets adhere to exposed subendothelial surfaces (via von Willebrand factor), become activated, release contents like ADP and thromboxane A2 to recruit more platelets, and aggregate to create a platelet plug. This plug is then strengthened by the coagulation cascade, which uses the platelet surface as a platform to generate fibrin that stabilizes the clot. Platelets also release factors that help with vasoconstriction, aiding hemostasis.

Other blood components handle different tasks: red blood cells transport oxygen, white blood cells fight infection, and enzymes like plasmin dissolve clots during fibrinolysis.