Final answer:
The initial phase of healing after an injury is the inflammation phase, during which the area gets red, swollen, and painful, signaling the body's preparatory response for later stages of healing.
Step-by-step explanation:
The first phase of healing after an injury occurs is the Inflammation phase. This response to injury is characterized by the injured area becoming red, warm, swollen, and painful due to injured cells and immune cells like mast cells and macrophages releasing chemical signals that cause vasodilation and fluid leakage in the surrounding tissue.
The inflammation is essential for preparing the groundwork for the subsequent phases of healing, which include the formation of blood clots, and the regeneration and repair of tissue where fibroblasts deposit collagen to rebuild the damaged area.