This is the u-shaped bone, so named from some resemblance to the Greek letter v. It is occasionally called the lingual bone, from its important relations with the tongue; it is situated at the base of the tongue, and may be felt between the chin and the thyroid cartilage. It consists of a body, two cornua, and two cornicula.
The body or central piece 1 is small, quadrilateral in its form, and appearing as if compressed from before backwards; hence the direction of its plane is nearly vertical; but the great cornua seem as if compressed from above downwards, so that their plane appears horizontal. The anterior surface of the body is convex, and marked at the middle by a vertical line, 1 on each side of which are depressions for the attachment of muscles; its posterior surface is concave, and corresponds with the epiglottis.
The cornua project backwards, and end in a rounded point. The cornicula, short, irregularly conical in their form, and oblique in their direction, are placed at the junction of the body with the cornua, and give attachment to the stylo-hyoid ligament; they continue for a long time movable, as the cartilage which connects them remains unossified to an advanced period of life.
Attachments of muscles and ligaments on the hyoid bone
The stylo-hyoid ligaments, to the cornicula; the thyro-hyoid, to the cornua. The anterior surface gives attachment to the stylo-hyoid, sterno-hyoid, and digastric muscles; the superior border, to the mylo-hyoid, genio-hyoid, genio-hyo-glossus, lingualis, hyo-glossus, and the middle constrictor of the pharynx; its lower border, to the omo-hyoid and thyro-hyoid muscles, and more internally to the thyro-hyoid membrane.
There are five points of ossification for the hyoids bones — one for each of its parts. Nuclei appear in the body and the great cornua towards the close of fetal life. Those which belong to the small cornua make their appearance sometime after birth.