Bone, Joint, and Muscle Disorders Chapter 46 Bones, Joints, and Muscles Bone is a constantly changing bodily tissue that has several functions. All the bones together make up the skeleton. The skeleton, muscles, tendons, ligaments, and other components of joints form the musculoskeletal system. The skeleton provides strength, stability, and a frame for muscles to work against in producing movement.
Bones also serve as shields to protect delicate internal organs.
But their internal structure is essentially the same. The hard outer part consists largely of proteins, such as collagen, and a substance called hydroxyapatite. Composed mainly of calcium and other minerals, hydroxyapatite stores much of the body's calcium and is largely responsible for the strength of bones. The marrow in the center of each bone is softer and less dense than the rest of the bone and contains specialized cells that produce blood cells. Blood vessels run through a bone, and nerves surround it.