is the response of the immune system
or irritation, characterized by redness, heat, swelling and pain. The redness and heat are caused by the increased blood
supply to the affected area. The blood vessels are dilated and engorged, and there is a loss of blood plasma
from them into the surrounding tissue spaces. This results in edema
or swelling. The swelling distends the tissues, compresses nerve
endings, and thus causes pain. The white blood cells
or leucocytes take an important role in inflammation; they escape the capillaries
, crowd the tissue spaces, and carry on their work as phagocytes picking up bacteria
debris. They aid in walling off an infection and preventing its spread.
When inflammation subsides, the damaged tissue is repaired. Depending on the severity of the inflammation and the type of tissue involved repairs may or may not be complete; in minor inflammations of the skin, for example, the tissue is capable of complete regeneration whereas in nervous tissue regeneration may be more limited and the damaged cells may be replaced with scar tissue.