Endosteum Connective tissue membrane covering internal bone surfaces Articular cartilage Hyaline cartilage covering bone ends at movable joints. Diaphysis Elongated shaft of a long bone. Tendon Cord of dense fibrous tissue attaching muscle to bone. Periosteum Double-layered connective tissue that covers and nourishes the bone. Osteocyte Mature bone cell. Osteogenesis The process of bone formation; also called ossification. Cartilaginous joints Bones united by cartilage; no joint cavity is present. Cartilage White, semiopaque connective tissue. Diploë The internal layer of spongy bone in flat bones. Epiphysis The end of a long bone, attached to the shaft. Osteoblasts Bone-forming cells. Osteoclasts Large cells that resorb or break down bone matrix. Adduct To move toward the midline of the body. Joint The junction of two or more bones. Chondrocyte Mature cell of cartilage. Rotation The turning of a bone around its own long axis. Medullary Central cavity of a long bone. Contains yellow or red (bone) marrow. Ligament Band of regular fibrous tissue that connects bones. Bursa A fibrous sac lined with synovial membrane and containing synovial fluid; occurs between bones and muscle tendons (or other structures), where it acts to decrease friction during movement. Synovial Freely movable joint exhibiting a joint cavity; also called a diarthrosis. Fibrous Bones joined by this tissue; no joint cavity is present. Abduct To move away from the midline of the body. Flexion Movement that decreases the angle of the joint, e.g., bending the knee from a straight to an angled position. Extension Movement that increases the angle of a joint, e.g., straightening a flexed knee.