Now that we’ve looked at the mandible and the principal muscles that move it, we’ll move on to look at a small but important bone that we haven’t seen yet, the hyoid bone.
The hyoid bone is a slender, U-shaped bone. It's suspended just beneath the mandible. It isn’t directly attached to any other bone. You can feel your own hyoid bone here, and you can move it from side to side.
Together with its attached muscles, the hyoid bone has two important functions: it holds up the tongue, which sits above it, and it holds up the larynx, which hangs below it. It also transmits the force of muscles that help to open the jaw. Let’s take a closer look at the hyoid bone.
This broad central part is the body. Its forward facing upper surface is convex, with facets for the attachment of numerous muscles that we’ll see shortly. The backward facing lower surface of the body is deeply concave.
On each side this long slender part of the hyoid bone is the greater horn or greater cornu. The greater horn is attached to the body by a small synovial joint, which gives it a little mobility. This small projection is the lesser horn, or lesser cornu.
When the structures above and below it are at rest, the hyoid bone lies slightly
below the lower border of the mandible. In the frontal plane the body of the hyoid is about in line with the last molar tooth.
From its resting position the hyoid bone can be moved upwards and downwards, and forwards and backwards, by the muscles that are attached to it.