When you hit your head why do you get a bump?

Question: When you hit your head why do you get a bump?
- Keywords:
  body
Asked by pokemaniac to Emma, Jimmy, Janet, Niall, Simon on 18 Mar 2013.
- Emma Ashley answered on 18 Mar 2013:
  
  When you hit you head you damage some of the cells and this causes inflammation in that area. Because the skull is hard the inflammation can’t go inwards and so is more obvious and shows itself as a bump.

Question: When you hit your head why do you get a bump?