Bone Function: Why Do We Have Bones? Medically reviewed by William Morrison, M.D. — Written by Jill Seladi-Schulman, ... The compact bone is the outer shell of the bone.

Surrounding the compact bone is the periosteum, ... We’ve known about this function since the 1950s. This part of bone also stores minerals until your body needs them–namely calcium and phosphate.

Compact bone: This hard and dense tissue makes up the outer layer of most bones and the main shaft of long bones, such as those in the arms and legs. Nerves and blood vessels live inside this tissue.