Final answer:
Histamine is responsible for causing the redness, swelling, and tenderness around a laceration due to its role in increasing blood flow and vascular permeability during the inflammatory response.
Step-by-step explanation:
The substance responsible for causing the redness, swelling, and tenderness around a leg laceration in an industrial accident is histamine. When tissue injury occurs, damaged cells release inflammatory chemical signals that lead to local vasodilation, or the widening of blood vessels. This increased blood flow results in the area becoming red and warm. Mast cells present in the tissue release histamine which intensifies the inflammatory response. The blood vessels also become more permeable under the influence of histamine, allowing white blood cells like neutrophils and macrophages, along with fluid, to move into the tissue spaces, causing swelling or edema. This swelling puts pressure on pain receptors, leading to the sensation of pain.