<P> The human musculoskeletal system (also known as the locomotor system, and previously the activity system) is an organ system that gives humans the ability to move using their muscular and skeletal systems . The musculoskeletal system provides form, support, stability, and movement to the body . </P> <P> It is made up of the bones of the skeleton, muscles, cartilage, tendons, ligaments, joints, and other connective tissue that supports and binds tissues and organs together . The musculoskeletal system's primary functions include supporting the body, allowing motion, and protecting vital organs . The skeletal portion of the system serves as the main storage system for calcium and phosphorus and contains critical components of the hematopoietic system . </P> <P> This system describes how bones are connected to other bones and muscle fibers via connective tissue such as tendons and ligaments . The bones provide stability to the body . Muscles keep bones in place and also play a role in the movement of bones . To allow motion, different bones are connected by joints . Cartilage prevents the bone ends from rubbing directly onto each other . Muscles contract to move the bone attached at the joint . </P> <P> There are, however, diseases and disorders that may adversely affect the function and overall effectiveness of the system . These diseases can be difficult to diagnose due to the close relation of the musculoskeletal system to other internal systems . The musculoskeletal system refers to the system having its muscles attached to an internal skeletal system and is necessary for humans to move to a more favorable position . Complex issues and injuries involving the musculoskeletal system are usually handled by a physiatrist (specialist in physical medicine and rehabilitation) or an orthopaedic surgeon . </P>

Which of the following structures or tissues is not part of the musculoskeletal system