Why do parts of human bodies swell after getting hurt?

Swelling is a natural inflammatory reaction of the body to injury. It occurs when damage occurs to the small blood vessels called capillaries which leak fluid into the surrounding tissue. The increased blood flow is largely responsible for the telltale symptoms of inflammation. The rush of warm blood as well as lymph causes redness, heat and swelling. At the same time, pressure from the swelling and the accumulation of immune cells, along with the destructive chemicals released by the cells, irritate local nerve endings and cause pain