What is the primary function of platelets in the blood?

The primary function of platelets in the blood is to facilitate blood clotting. Platelets, or thrombocytes, are small cell fragments that play a crucial role in hemostasis, the process that prevents and stops bleeding. When a blood vessel is injured, platelets quickly gather at the site of the damage, adhering to the broken vessel wall and to each other. This aggregation forms a temporary plug that helps to seal the wound. In addition to their aggregation function, platelets release chemical signals that further promote clotting and recruit more platelets to the site of injury, forming a stable blood clot.

The other functions mentioned, such as transporting oxygen to cells and regulating blood pressure, are carried out by red blood cells and blood vessels, respectively. The production of antibodies is a function of the immune system, specifically by B-cells, and is unrelated to the role of platelets. Thus, the correct answer emphasizes the critical role platelets play in maintaining hemostatic balance and preventing excessive blood loss.