L'os hyoïde

The hyoid bone is a U-shaped bone positioned in the anterior neck between the mandible and larynx. It sits at the level of the inferior mandible with its tips pointing posteriorly. Unlike other bones, the hyoid is suspended by stylohyoid ligaments from the styloid processes of the skull and has no direct connection to any other bone.

The hyoid bone consists of a central horizontal body with a convex anterior and concave posterior surface. Two pairs of horn-like projections called cornua extend from the body: the greater cornua attach to the lateral ends and project posterolaterally, while the smaller lesser cornua are tiny conical projections that project laterally and upward.

The hyoid bone serves as the attachment site for muscles of the tongue, larynx, and pharynx. Small muscles attached above or below move the hyoid up, down, forward, or backward in coordination with tongue, larynx, and pharynx movements during swallowing and speaking, making it essential for these functions.

The hyoid bone is vital for airway patency. The region between the oropharynx above and tracheal rings below the hyoid helps maintain an open airway. Additionally, the hyoid connects to the larynx and supports respiratory functions through its attachment to muscles controlling airway positioning during breathing.

Hyoid ossification begins toward the end of fetal development, starting in the greater cornua and completing in the body shortly after birth. The fibrous material connecting the greater cornua to the body ossifies later, toward middle age, making the hyoid unique in its prolonged ossification timeline.

The hyoid bone aids digestive functions by supporting tongue movement and mastication through muscle attachments. It also plays a critical role in swallowing and preventing regurgitation by coordinating movements of the pharynx and larynx, making it integral to the orofacial complex.

The stylohyoid ligaments suspend the hyoid from the styloid processes of the skull. The greater cornua attach stylohyoid and thyrohyoid muscles and ligaments, while the lesser cornua connect to the body through fibrous tissue. These attachments enable the hyoid to move and support functions of the tongue, larynx, and pharynx.