Mrs. Abbruzzo brought her 4-year-old daughter to the doctor, complaining that she didn't "look right:' The child's forehead was enlarged, her rib cage was knobby, and her lower limbs were bent and deformed. X rays revealed very thick epiphyseal plates. Mrs. Abbruzzo was advised to increase dietary amounts of vitamin D and milk and to "shoo" the girl outside to play in the sun. Considering the child's signs and symptoms, what disease do you think she has? Explain the doctor's instructions. The process called bone remodeling involves both osteoblasts and osteoclasts. What do each of these cells do? What would a long bone look like at the end of adolescence if the osteoclasts didn't do their job? Why do you think wheelchair-bound people with paralyzed lower limbs have thin, weak bones of the leg and thigh? Old Norse stories tell of a famous Viking named Egil, who lived around 900 AD. His skull was greatly enlarged and misshapen, and the cranial bones were thickened (6 cm, more than 2 inches, thick). After he died, his skull was dug up and it withstood the blow of an ax without damage. In life, he had headaches from the pressure exerted by enlarged vertebrae on his spinal cord. So much blood was diverted to his bones to support their extensive remodeling that his fingers and toes always felt cold and his heart was damaged through overexertion. What bone disorder did Egil probably have?