Final answer:
The primary response to stop bleeding is the formation of a blood clot during hemostasis. The next step after clot formation is tissue repair and healing. Platelets are key in developing the clot to seal the injury and prevent hemorrhage.
Step-by-step explanation:
The primary (first) response to stop bleeding after a skin injury is hemostasis which includes the formation of a blood clot. This response initiates with a vascular spasm that constricts the blood flow, followed by the formation of a platelet plug, and finally, coagulation or blood clotting. After the blood clot forms, the next responses are the repair and healing of the tissue.
Platelets play a crucial role in this process. They adhere to the site of injury and release chemicals that help in attracting more platelets, which contributes to the formation of the clot. If the bleeding is not controlled by these mechanisms, it can result in hemorrhage, where blood pressure and blood volume may drop to critically low levels, requiring medical intervention to restore blood volume and maintain perfusion to vital organs.