A platelet plug is a temporary structure formed during the body's response to a blood vessel injury. When a blood vessel is damaged, it exposes the underlying tissue, which triggers the activation of platelets, small cell fragments in the blood. These platelets quickly adhere to the injury site and to each other, forming a sticky mass that helps to seal the wound and prevent further bleeding. The formation of a platelet plug is the first step in the hemostasis process, which is essential for stopping bleeding. Once the plug is formed, it provides a surface for other components of the coagulation cascade to act, ultimately leading to the formation of a stable blood clot.