ANATOMY

Unlike other bones Hyoid bone is jointed to other bones with muscles or ligaments only. Hyoid bone is supported by muscles from anterior, posterior and inferior sides aiding in tongue in its movement and swallowing. It provides muscle attachments to the Floor of Mouth, tongue above, Larynx below and Epiglottis and Pharynx in behind. Hyoid bone consists of a central body and two pair of horns i.e.

• Body

• Greater Horns

• Lesser Horns

HORNS

The greater and lesser Horns are two part of a bone that arises from Hyoid. Greater Horns arise from the back of the outer borders of the Body and are flattened from above. The upper surface of these horns is rough and helps in muscle attachment. The muscles attached to the upper surface of Greater Horns are Hypoglossus and Constrictor Pharyngis Medius which goes along the whole length of Cornu (Horn). Greater Horns are derived from the third Pharyngeal Arches.

The Lesser Horns are two small, cone shaped projections that attach themselves to the angle of junction between Body and Greater Horns of Hyoid Bone by their bases. Lesser Horns are connected to the Body of bone with a fibrous tissue and sometimes with Greater Horns by prominent Diarthrodial Joints. The apex of each horn gives attachments to the Stylohyoid Ligament. The Lesser Horns are derived from the second Pharyngeal Arches.

DEVELOPMENT

The ossification of Hyoid starts from six centers; two for Body and one for each Horn. Ossification of Greater Horn commences during the end of Fetal Life, the Body’s ossification ends shortly afterwards and the Lesser Horn during the first or second year of birth. The connection between Body and Greater Horn is fibrous until middle age.

MUSCLE ATTACHMENTS

There are total of nine muscles attached to the Hyoid bone base on their superiority and inferiority which are as follows.

• Middle Pharyngeal Constrictor Muscle

• Hyoglossus Muscle

• Digastric Muscle

• Stylohyoid Muscle

• Geniohyoid Muscle

• Mylohyoid Muscle

• Thyrohyoid Muscle

• Omohyoid Muscle

• Stemohyoid Muscle

FUNCTION

Hyoid bone is present in many mammals. It allows a wider surface for tongue, Pharyngeal and Laryngeal movements by holding all these structures alongside each other to produce variation.

FRACTURES

Due to its anatomical position Hyoid bone is not easily exposed to fractures. In a suspicion of murder, the fracture of Hyoid bone indicates Strangulation or Throttling. However this suspicion is rejected in case of children and newly born babies as the Hyoid bone is still flexible and in ossification stage.