Hyoid bone

At a glance

English

Hyoid bone

Latin (TA2)

Os hyoideum

System

Bone

Region

Head

Side

Single, on the midline

About the hyoid bone

The hyoid is a small, U-shaped bone lying across the front of the neck, between the lower border of the mandible and the thyroid cartilage of the larynx. At rest it is level with the third cervical vertebra behind. It is unusual in having no joint with any other bone: it hangs in a sling of muscles and ligaments that run to the skull, the jaw, the larynx, the sternum and the scapula.

It consists of a central body with a greater and a lesser horn on each side. The body is a curved bar whose front face looks forwards and up and is crossed by a horizontal ridge, often with a faint vertical ridge in the midline. Geniohyoid inserts over most of that front face, while mylohyoid, sternohyoid and omohyoid attach below the ridge. The back of the body is smooth and hollow and lies in front of the epiglottis, with the thyrohyoid membrane, loose tissue and a small bursa in between. The greater horns run backwards from the ends of the body, flattened and tapering to a small tubercle; hyoglossus and the middle constrictor of the pharynx arise along them, and thyrohyoid inserts on their outer edge. The lesser horns are small cones at the junction of body and greater horn, tied by the stylohyoid ligaments to the styloid processes of the skull.

Because the muscles above (the suprahyoid group) and below (the infrahyoid group) pull on it from several directions, the hyoid acts as a mobile base for the tongue and the larynx. It rises and moves forward in swallowing, drawing the larynx up under the epiglottis, and its position also helps keep the upper airway open. A low-lying hyoid has been linked with obstructive sleep apnoea, and some airway operations hitch it forwards or upwards.

The bone develops from the second and third pharyngeal arches: the lesser horns and upper body from the second, the greater horns and lower body from the third. The joints between body and greater horns stay fibrous or cartilaginous until middle age and then usually fuse. Lying sheltered under the jaw, the hyoid is seldom broken; a fracture in an adult strongly suggests that the neck has been squeezed, a finding used in forensic examination.

Function and supply

Function

Serves as a movable anchor for the tongue, floor of the mouth, pharynx and larynx, raising and steadying them during swallowing and speech.

Nerve supply

Not innervated as a muscle is; the hypoglossal nerve runs along the hyoglossus just above the greater horn, and the muscles attached to the bone are supplied by the trigeminal, facial, hypoglossal and cervical (ansa cervicalis) nerves.

Blood supply

The lingual artery runs back along the greater horn, and its suprahyoid branch follows the upper border of the body; the superior thyroid artery supplies the lower attachments.