What is the primary function of platelets in the human body?

Platelets, also known as thrombocytes, are small cell fragments in the blood crucial for the process of hemostasis, which is the cessation of bleeding. Their primary function involves forming blood clots to prevent excessive bleeding when blood vessels are injured. When a blood vessel is damaged, platelets quickly aggregate at the site of injury, adhering to the exposed tissues and each other, which leads to the formation of a temporary "platelet plug". This process activates other components of the coagulation cascade, ultimately resulting in the formation of a stable blood clot.

This function is vital for maintaining proper blood flow and healing wounds, as it prevents blood loss and allows the body to begin the repair process. In contrast, the other options presented do not relate to platelets' primary role: transporting oxygen is the function of red blood cells; fighting infections is primarily the role of white blood cells; and hormone production is typically associated with endocrine glands. Thus, the role of platelets as key players in blood clotting establishes them as essential components of the body's response to injury.