Introduction

The hyoid bone (os hyoideum) derives its name from the Greek hyodeides, meaning "shaped like the letter upsilon" (U-shaped). It is a small, unpaired, horseshoe-shaped bone situated in the anterior midline of the neck beneath the tongue, between the mandible and the larynx at the level of the fourth cervical vertebra (C4).

The hyoid is unique in that it is the only bone in the human skeleton that does not articulate directly with any other bone. Instead, it is suspended and anchored to surrounding structures (larynx, pharynx, shoulder girdle, tongue, and sternum) purely via muscles and ligaments. It serves as a key landmark dividing the anterior neck muscles into two functional groups: suprahyoid muscles (above) and infrahyoid muscles (below). The hyoid bone plays an active role in respiration, phonation, deglutition (swallowing), mastication, tongue movement, and head support.

Ligamentous and Fascial Connections:

• Stylohyoid ligament (ligamentum stylohyoideum): Connects the lesser horn of the hyoid to the tip of the styloid process of the temporal bone.
• Thyrohyoid membrane (membrana thyrohyoidea): Suspends the larynx from the hyoid bone, reinforced by the median and lateral thyrohyoid ligaments (lig. thyrohyoideum medianum et laterale).
• Hyoepiglottic ligament (ligamentum hyoepiglotticum): Connects the hyoid to the anterior surface of the epiglottis.
• Cervical fascia: Anchors the hyoid to the cervical spine via the deep cervical fascia.

Muscular Attachments

Suprahyoid Muscle Group:

• Digastric muscle (m. digastricus)
• Stylohyoid muscle (m. stylohyoideus)
• Mylohyoid muscle (m. mylohyoideus)
• Geniohyoid muscle (m. geniohyoideus)

Infrahyoid Muscle Group:

• Sternohyoid muscle (m. sternohyoideus)
• Omohyoid muscle (m. omohyoideus)
• Thyrohyoid muscle (m. thyrohyoideus)
• Middle pharyngeal constrictor (m. constrictor pharyngis medius)
• Genioglossus muscle (m. genioglossus)
• Hyoglossus muscle (m. hyoglossus)

Anatomical Features

• Body (Corpus): The central, quadrangular, irregularly shaped portion situated between the two horns (forming the arch of the "U"). Its anterior surface is convex and marked by a central vertical median ridge, while its posterior surface is concave and smooth.
• Lesser Horn (Cornu minus): Paired, small, conical bony projections pointing posterosuperiorly from the junction of the body and greater horns. The tip of each lesser horn gives attachment to the stylohyoid ligament.
• Greater Horn (Cornu majus): Paired, long, flattened processes projecting posterolaterally from the lateral margins of the body to form the limbs of the "U." They are broader proximally and taper distally to end in a small tubercle, which gives attachment to the lateral thyrohyoid ligament.

Note: The horns are connected to the body during early life by cartilaginous joints (synchondroses) or occasional synovial joints, which progressively undergo synostosis (bony fusion) in adulthood.