Tendons are fibers that coonect the muscles with the bones and are part of the skeletal system. The human skeletal system consists of bones, cartilage, ligaments and tendons and accounts for about 20 percent of the body weight. Tendons may also attach muscles to structures such as the eyeball. A tendon serves to move the bone or structure. A ligament is a fibrous connective tissue which attaches bone to bone, and usually serves to hold structures together and keep them stable.