If you didn't have a skeletal system, you'd probably look (and feel) like a giant, hairy water balloon that would jiggle and wobble if someone poked at you. Pretty picture, huh? The human skeletal system consists of bones, cartilage, and the membranes that line the bones. Each bone is an organ that includes connective tissue (bone, blood, cartilage, adipose tissue, and fibrous connective tissue), nervous tissue, and muscle and epithelial tissues (within the blood vessels).
The three main functions of the skeletal system are
Support. Bones provide a framework for the attachment of muscles and other tissues.
Movement. Bones enable body movements by acting as levers and points of attachment for muscles.
Bones such as the skull and rib cage protect vital organs from injury. Bones also protect the marrow.
Mineral storage. Bones serve as a reservoir for calcium and phosphorus, essential minerals for various cellular activities throughout the body.
Blood cell production. The production of blood cells, or hematopoiesis, occurs in the red marrow found within the cavities of certain bones.
Energy storage. Lipids (fats) stored in adipose cells of the yellow marrow serve as an energy reservoir.
The whole package of bones, cartilage, ligaments, and tendons that make up the human skeletal system account for about 20 percent of our body weight — not much for the big job of keeping us moving and healthy (and looking a whole lot better than bags of gelatin)!