The periosteum is the tough, vascular membrane which covers the surface of a bone, except for the |articular cartilage|. The periosteum contains the ~blood~ vessels which supply nutrients to the bones enabling them to regenerate. The bones of the |skull| feature no such periosteum, and so cannot regenerate themselves. The periosteum also facilitates the regeneration of bone by serving as a confining membrane for the deposition of new bone cells, insuring that any regeneration of osseous material is added to the pre-existing bone.
