A 75-year-old woman and her 9-year-old granddaughter were victims of a train crash. In both cases, trauma to the chest was sustained. X-rays of the grandmother revealed several fractured ribs, but her granddaughter had no fractured ribs. Why are the injuries different for the granddaughter and grandmother?

For a 75-year-old woman, several fractures were revealed because of the low concentration of organic matter in bones which makes bones bend slightly. Also, grandmother bones extensively calcified to make them stiff but for 9-year granddaughter, bones are rich in organic matter, therefore, she had no fractured ribs.