Functions of bone include support for soft tissues and organs, protection of organs such as the brain and spinal cord, body movement, and hematopoiesis. Skeletal muscles are composed of muscle fibers that attach to bones to facilitate movement. Joints are articulations where two or more bones come together. Joints are classified by the type of material between them and by their degree of movement. The difference between ligaments and tendons is more functional than structural. Cartilage is a semismooth, gel like tissue that is strong and able to support weight. The six bones of the cranium (frontal, parietal, temporal, and occipital) are fused together. The trunk is formed by the vertebrae, ribs, and sternum of the axial skeleton and the scapula and clavicle of the appendicular skeleton. The shoulder joint, also called the glenohumeral joint, consists of the point where the humerus and the glenoid fossa of the scapula articulate.