Tendons connect muscles to bones. Tendons are also made up of fibers, but these fibers do not stretch or shrink. The tendons transfer the force from the muscle to move the bone. Some tendons, like those in the wrist and hand, are covered with a sheath that contains a lubricating fluid. These tendons pass back and forth through the sheath as the muscles tighten or relax.
Ligaments connect bones to form a joint.
Joints are covered by ligaments that form a joint capsule which holds the ends of the bones together and allows movement. The joint also contains lubricating fluid. Some ligaments, such as those in the shoulder, elbow, and knee are shielded from friction by a bursa , a small sac filled with fluid. Nerves carry messages throughout the body. The nerves send and receive information to and from the brain.