Hyoid bone

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Hyoid bone
Gray186.png
Hyoid bone. Anterior surface. Enlarged.
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Anterolateral view of head and neck.
Latin os hyoideum
Gray's p.177
Precursor 2nd and 3rd branchial arch1
MeSH Hyoid+Bone
TA A02.1.16.001
FMA FMA:52749
Anatomical terms of bone

The hyoid bone (lingual bone) (/ˈhɔɪd/;23 Latin os hyoideum) is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra (C3) behind.

Unlike other bones, the hyoid is only distantly articulated to other bones by muscles or ligaments. The hyoid is anchored by muscles from the anterior, posterior and inferior directions, and aids in tongue movement and swallowing. The hyoid bone provides attachment to the muscles of the floor of the mouth and the tongue above, the larynx below, and the epiglottis and pharynx behind.

Its name is derived from the Greek word hyoeides meaning "shaped like the letter upsilon" (υ).

Structure

The bone consists of a central part called the body, and two pairs of horns, the greater and lesser horns.

Horns

The lesser and greater horns of the hyoid

The greater and lesser horns (Latin: cornu) are two sections of bone that project from the hyoid.

The greater horns project backward from the outer borders of the body; they are flattened from above downward and taper to their end, which is a bony tubercle connecting to the lateral hyothyroid ligament. The upper surface of the greater horns are rough and close to its lateral border, and facilitates muscular attachment. The largest of muscles that attach to the upper surface of the greater horns are the hyoglossus and constrictor pharyngis medius, which extend along the whole length of the cornu; the digastric muscle and stylohyoid muscle have small insertions in front of these near the junction of the body with the cornu. To the medial border the hyothyroid membrane is attached, while the anterior half of the lateral border gives insertion to the thyrohyoid. The greater cornua derive from the third pharyngeal arches.citation needed

The lesser horns are two small, conical eminences, attached by their bases to the angles of junction between the body and greater horns of the hyoid bone. They are connected to the body of the bone by fibrous tissue, and occasionally to the greater cornua by distinct diarthrodial joints, which usually persist throughout life, but occasionally become ankylosed. The lesser cornua are situated in the line of the transverse ridge on the body and appear to be morphological continuations of it. The apex of each cornu gives attachment to the stylohyoid ligament; the Chondroglossus rises from the medial side of the base. The lesser cornua are derived from the 2nd pharyngeal arches.citation needed

Development

The second pharyngeal arch gives rise to the lesser cornu of hyoid and the superior part of body of hyoid. The cartilage of the third pharyngeal arch forms the greater cornu of hyoid and the lower portion of the body of hyoid.

The hyoid is ossified from six centers: two for the body, and one for each cornu. Ossification commences in the greater cornua toward the end of fetal life, in the body shortly afterward, and in the lesser cornua during the first or second year after birth. Until middle age the connection between the body and greater cornu is fibrous.

Muscle attachments

The following muscles are attached to the hyoid:

Function

The hyoid bone is present in many mammals. It allows a wider range of tongue, pharyngeal and laryngeal movements by bracing these structures alongside each other in order to produce variation.4 Its descent in living creatures is not unique to Homo sapiens, and does not allow the production of a wide range of sounds: with a lower larynx, men do not produce a wider range of sounds than women and 2 year old babies. Moreover the larynx position of Neanderthal was not a handicap to producing speech sounds.5 The discovery of a modern-looking hyoid bone of a Neanderthal man in the Kebara Cave in Israel led its discoverers to argue that the Neanderthals had a descended larynx, and thus human-like speech capabilities.6 However, other researchers have claimed that the morphology of the hyoid is not indicative of the larynx's position.7 It is necessary to take into consideration the skull base, the mandible and the cervical vertebrae and a cranial reference plane.89

Clinical significance

Due to its position, the hyoid bone is not susceptible to easy fracture. In a suspected case of murder, a fractured hyoid strongly indicates throttling or strangulation in an adult. However, this is not necessarily the case in children and adolescents, where the hyoid bone is still flexible as ossification is yet to be completed.

In other animals

The hyoid bone is derived from the lower half of the second gill arch in fish, which separates the first gill slit from the spiracle, and is often referred to as the hyoid arch. In many animals, it also incorporates elements of other gill arches, and has a correspondingly greater number of cornua. Amphibians and reptiles may have many cornua, while mammals (including humans) have two pairs, and birds only one. In birds, and some reptiles, the body of the hyoid is greatly extended forward, creating a solid bony support for the tongue.10 The howler monkey Alouatta has a pneumatized hyoid bone, one of the few cases of postcranial pneumatization of bones outside Saurischia.

The hyoid bone of a gecko with attached tracheal rings 
Hyoid bones of various birds. 

Additional images

See also

This article uses anatomical terminology; for an overview, see anatomical terminology.

References

This article incorporates text from a public domain edition of Gray's Anatomy.

  1. ^ hednk-023 — Embryo Images at University of North Carolina
  2. ^ OED 2nd edition, 1989.
  3. ^ Entry "hyoid" in Merriam-Webster Online Dictionary.
  4. ^ http://www.pnas.org/cgi/content/full/100/12/6930 Descent of the larynx in chimpanzee infants
  5. ^ Boë, L.J. et al. The potential of Neandertal vowel space was as large as that of modern humans. Journal of Phonetics 30 (2002) 465–484.
  6. ^ Arsenburg, B. et al., A reappraisal of the anatomical basis for speech in middle Paleolithic hominids, in: American Journal of Physiological Anthropology 83 (1990), pp. 137–146.
  7. ^ Fitch, Tecumseh W., The evolution of speech: a comparative review, in: Trends in Cognitive Science, Vol. 4, No. 7, July 2000 (http://www3.isrl.uiuc.edu/~junwang4/langev/localcopy/pdf/fitch00speech.pdf)
  8. ^ Granat et al., Hyoid bone and larynx in Homo. Estimated position by biometrics, Biom. Hum. et Anthropolol., 2006, 24, 3-4, 243–255.
  9. ^ Boë, L.J. et al., Variation and prediction of the hyoid bone position for modern Man and Neanderthal, Biom. Hum. et Anthropolol., 2006, 24, 3-4, 257–271
  10. ^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. p. 214. ISBN 0-03-910284-X. 

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