What is the role of platelets in blood?

• A. They transport oxygen in the blood.
• B. They regulate blood glucose levels.
• C. Platelets play an important role in hemostasis.
• D. They release antibodies to pathogens.

Answer: (C)

Platelets are small cell fragments that play a key role in stopping bleeding, a process called hemostasis. When a blood vessel is damaged, they quickly adhere to exposed collagen with the help of von Willebrand factor, become activated, and release substances like ADP, thromboxane A2, and serotonin to recruit and activate more platelets. They then aggregate, using fibrinogen bridges between platelets, to form a platelet plug that seals the injury. This plug provides the initial, temporary barrier, and is later strengthened by the coagulation cascade that converts fibrinogen to fibrin to stabilize the clot. Platelets also release growth factors that aid in vessel repair. The other options don’t fit because oxygen transport is handled by red blood cells, glucose regulation by metabolic hormones, and antibodies by immune cells.