What is the primary function of platelets?

The primary function of platelets is clotting blood. Platelets, also known as thrombocytes, are small, disc-shaped cell fragments that play a crucial role in hemostasis, the process that prevents and stops bleeding. When a blood vessel is injured, platelets quickly accumulate at the site of the injury. They adhere to the exposed collagen in the damaged vessel wall and to each other, forming a temporary "platelet plug." Additionally, these platelets release various chemicals that further accelerate the clotting process and enhance the recruitment of more platelets to the area, leading to a stable blood clot formation.

This function is vital in preventing excessive blood loss from injuries and ensuring that the body maintains vascular integrity. While the other options involve important biological processes—such as transporting oxygen and carbon dioxide by red blood cells and fighting infections through white blood cells—they do not pertain to the specific role of platelets in hemostasis and blood clotting.