Periosteum: The Protective Outer Bone Covering - Definition & Function

The correct answer is the Periosteum.

The periosteum is a dense, fibrous connective tissue that covers and protects the outer surface of all bones, except at the joints. It is composed of two layers: an outer fibrous layer and an inner cellular layer. The fibrous layer is composed of dense collagen fibers that provide strength and protection, while the cellular layer contains osteoblasts, which are cells that build new bone, and osteoclasts, which are cells that break down old bone. The periosteum also contains blood vessels and nerves that supply the bone with oxygen and nutrients.