

The long bones’ tubular design provides maximum strength with minimum weight. This cavity minimizes the weight of the bone by reducing the dense bony material where it is least needed. The medullary cavity (medulla- = marrow), or marrow cavity, is a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels in adults.The periosteum is attached to the underlying bone by perforating fibers or Sharpey’s fibers, thick bundles of collagen that extend from the periosteum into the bone extracellular matrix. The periosteum also protects the bone, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons. Some of the cells enable bone to grow in thickness, but not in length. It is composed of an outer fibrous layer of dense irregular connective tissue and an inner osteogenic layer that consists of cells. The periosteum is a tough connective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage.Because articular cartilage lacks a perichondrium and lacks blood vessels, repair of damage is limited.

Articular cartilage reduces friction and absorbs shock at freely movable joints.

Long bones have a thick outside layer of compact bone and an inner medullary cavity containing bone marrow. A long bone is a bone that has greater length than width.
