STAGES OF INFLAMMATION
Inflammation is a body defense mechanism that occurs regardless of the source
of injury. The inflammatory response is progressive, in stages; however, it should be
realized that various stages may exist within an injured area at the same time. The
major stages in the inflammatory process are vascular change, exudation, and repair.
The initial inflammatory response is vascular tissue injury resulting in the following
sequence of events.
a. Hyperemia. The presence of an abnormally large blood supply in which the
blood vessels are dilated and the flow of blood is slower.
b. Permeability. Increased permeability in the smaller blood vessels, allowing
the body to position blood elements in the area in order to heal the injured tissue or
combat any introduced foreign agents.
c. Exudation. The movement of fluid and blood cellular elements (exudates)
into the injured tissue(s).
d. Edema. Accumulation of fluids within the tissue(s) that then slows or
stagnates blood flow. This acts to localize the inflammatory process.
MAJOR SIGNS AND SYMPTOMS OF INFLAMMATION
The four major signs and symptoms of inflammation are swelling, pain, heat, and
redness. Sometimes a fifth sign is disturbance of function. Swelling is the visual sign of
the accumulation of inflammatory substances (exudates) in the tissues and the
increased amount of blood in the area. The pressure of the exudates (and perhaps the
action of toxins, enzymes, and acids released from injured cells or liberated by
defensive cellular elements) on the nerve endings causes pain. The redness and heat
that accompany inflammation are because of the increased amount of blood in the area.
Inflammatory involvement of the tissue may result in disturbance of function.
BENEFICIAL EFFECTS OF INFLAMMATION
The beneficial effects of inflammation are essentially fourfold. First, the
increased fluid dilutes the irritants present in the area (e.g., bacteria and their poisonous
products). Second, the blood cells engulf and often digest bacteria, dead cells, or other
debris that might cause or continue the inflammation. Third, antibodies, which are also
present in the edema fluid, neutralize toxic substances. Fourth, clotting of the edema
fluid walls off the area and prevents the irritant and the inflammation or the inflammatory
process from spreading beyond the affected site.