The inflammatory response:
1. prevents the spread of damaging agents to nearby tissues
2. disposes of cell debris and pathogens
3. sets the stage for the repair process.
The four cardinal signs of inflammation are redness, heat, swelling and pain. Many experts consider impairment of function to be the fifth cardinal sign of inflammation.
The inflammatory process begins with chemical “alarms” a series of inflammatory chemicals that are released in the extracellular fluid. Injured tissue cells, phagocytes, lymphocytes, mast cells and blood proteins are all sources of inflammatory mediators, the most important of which are histamine, kinins, prostaglandins, complement, and lymphokines.
Though some of these mediators have individual inflammatory roles as well, they all promote dilation of the small blood vessels in the vicinity of the injury. As more blood flows into the area local hyperemia (congestion with blood) occurs which accounts for the redness and the heat of the inflamed area.
These chemicals also increase the permeability of local capillaries. Consequently, exudates, fluid containing proteins such as clotting factors and antibodies, seeps from the bloodstream into the tissue spaces.
This exudate is the cause of the local oedema or swelling that in turn, presses on adjacent nerve endings, contributing to a sensation of pain. Pain also results from the release of bacterial toxins, lack of nutrition to the cells in the area, and the sensitising effects of released prostaglandins and kinins. If the swollen and painful area is a joint, normal movement may be inhibited temporarily in order for proper healing and repair to occur.