The skeletal system is the body system composed of bones, cartilage, ligaments and other tissues that perform essential functions for the human body. Bone tissue is a hard, dense connective tissue that forms most of the adult skeleton, the internal support structure of our body. In the areas of the skeleton where whole bones move against each other (for example, joints like the shoulder or between the bones of the spine), cartilage, a semi-rigid form of connective tissue, provide flexibility and smooth surfaces for movement. Ligaments are composed of dense connective tissue surround these joints, tying skeletal elements together, connecting bones to other bones.1 Together, they perform the several functions of the skeletal system.
Many people think of bones as being dead, dry, and brittle. These adjectives correctly describe the bones of a preserved skeleton, but the bones in a living human being are very much alive. The basic structure of bones is bone matrix, which forms the underlying rigid framework of bones, formed of both compact and spongy bone. The bone matrix consists of tough protein fibers—mainly collagen—that become hard and rigid due to mineralization with calcium crystals. Bone matrix is crisscrossed by blood vessels and nerves and contains specialized bone cells that are actively involved in metabolic processes.2
