Final answer:
The redness seen in injured skin is caused by vasodilation and increased blood flow to the damaged area, as part of the inflammatory response to help with healing and combat infections.
Step-by-step explanation:
Injured skin is inflamed and looks red because the nearby blood vessels dilate, or expand, which increases blood flow to the damaged area. This process is part of the body's inflammatory response to injury or infection, causing the area to become red, warm, and sometimes painful.
When skin or other tissues are damaged, cells release chemical signals such as histamine that lead to vasodilation. This response brings more blood, along with immune cells like phagocytes and neutrophils, to the site of the injury. The increased blood flow and the leakage of fluids from the blood vessels into the tissue result in the classic signs of inflammation: redness, warmth, swelling, and pain. Additionally, this process helps to bring nutrients and immune cells to the site of the injury to facilitate the healing process and to fight off any potential infections.