Final answer:
The observable characteristics of vascular injury and inflammation are redness, warmth, increased swelling, and pain, which occur due to increased blood flow and vascular permeability and are part of the body's innate immune response.
Step-by-step explanation:
The observable characteristics of vascular injury and inflammation include redness, warmth to the touch, increased swelling, and pain. These symptoms are driven by the body's response to injury or infection, involving increased blood flow and vascular permeability, as well as the immune system's reaction to such events. Coolness to the touch is not an indicator of inflammation; warmth is typically observed due to increased blood flow. In contrast, coolness might suggest a reduction in blood flow or a different underlying condition.
The four cardinal signs of inflammation, noted since antiquity and ascribed to Cornelius Celsus, are redness, swelling, pain, and local heat. Sometimes loss of function is mentioned as a fifth characteristic. Essential to the innate immune response, inflammation is a complex biological process that involves various cells and chemical mediators that produce these symptoms to contain damage, remove debris, and begin the process of tissue repair.
In summary, fever is a systemic sign of inflammation but not a direct local sign at the site of inflammation. The increase in vascular permeability and vasodilation from mediators like histamine leads to the observed symptoms, with the key purpose of facilitating the repair and recovery of the damaged tissue.