The hyoid bone is a U-shaped bone located at the front of the neck near the root of the tongue, between the lower jaw and the biggest cartilage of the larynx, or voice box. The hyoid bone's principal role is to act as an attachment structure for the tongue and muscles in the oral cavity floor. It also contributes to the formation of the pharyngeal wall. The soft tissue of the tongue also contains many muscle fibers that can be divided into two groups: extrinsic and intrinsic. The intrinsic muscles surround the central shaft of the tongue and attach to it. They include the longitudinal muscle, which runs the length of the tongue and helps it move back and forth; the transverse muscle, which runs across the tongue from side to side and helps it rotate; and the vertical muscle, which lies beneath the surface of the tongue and raises it up. The extrinsic muscles cover the sides of the tongue. These include the superior trapezius muscle, which attaches to the skull just above the ear; the middle trapezius muscle, which connects with the spine at the base of the skull; and the inferior trapezius muscle, which ends in the sternum (breastbone). In addition to acting as a muscular organ of taste, the tongue is also involved in speech production and swallowing. It begins moving toward the roof of the mouth when someone wants to speak or swallow. The human tongue is made up of multiple flat plates called linguals.