Does anyone know why an infection or broken bone becomes hot and swollen?

Answer 1

This is the local adaptation syndrome. Dolor - pain Rubar - Redness Calor - heat and Turgor - swelling. It is a response to local tissue insult. The permeability of the vessels in the area goes down so that immune cells can move into the tissues (swelling) and the increased blood flow to the area causes heat. Generalized fervor usually follows as a result of chemical cues released by the injured tissue. These same type of cues call specialized cells to the area.