Hyoid bone

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Hyoid
712 Hyoid Bone.jpg
The hyoid bone, present at the front of the neck, has a body and two sets of horns
Details
Precursor 2nd and 3rd branchial arch [1]
Identifiers
Latin os hyoideum
MeSH D006928
TA98 A02.1.16.001
TA2 876
FMA 52749
Anatomical terms of bone

The hyoid bone (lingual bone or tongue-bone) ( /ˈhɔɪd/ [2] [3] ) is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebra.

Contents

Unlike other bones, the hyoid is only distantly articulated to other bones by muscles or ligaments. It is the only bone in the human body that is not connected to any other bones nearby. 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.[ citation needed ]

Its name is derived from Greek hyoeides 'shaped like the letter upsilon (υ)'. [4] [5]

Structure

Hyoid bone - animation.gif
Hyoid bone - close-up - animation.gif
Left: Position of hyoid bone (shown in red). Right: Shape of hyoid bone.

The hyoid bone is classed as an irregular bone and consists of a central part called the body, and two pairs of horns, the greater and lesser horns.

Body

The body of the hyoid bone is the central part of the hyoid bone.[ clarification needed ]

Horns

The lesser and greater horns of the hyoid Gray186.png
The lesser and greater horns of the hyoid

The greater and lesser horns (Latin : cornua) are two sections of bone that project from each side of 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 thyrohyoid 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 the middle pharyngeal constrictor, which extend along the whole length of the horns; the digastric muscle and stylohyoid muscle have small insertions in front of these near the junction of the body with the horns. To the medial border the thyrohyoid membrane is attached, while the anterior half of the lateral border gives insertion to the thyrohyoid muscle.[ 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 horns by distinct diarthrodial joints, which usually persist throughout life, but occasionally become ankylosed. The lesser horns are situated in the line of the transverse ridge on the body and appear to be continuations of it. The apex of each horn gives attachment to the stylohyoid ligament; the chondroglossus rises from the medial side of the base.[ citation needed ]

Development

The second pharyngeal arch, also called the hyoid arch, gives rise to the lesser cornu of the hyoid and the upper part of the body of the hyoid. The cartilage of the third pharyngeal arch forms the greater cornu of the hyoid and the lower portion of the body of the 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 development, in the hyoid 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.

In early life the outer borders of the body are connected to the greater horns by synchondroses; after middle life usually by bony union.

Blood supply

Blood is supplied to the hyoid bone via the lingual artery, which runs down from the tongue to the greater horns of the bone. The suprahyoid branch of the lingual artery runs along the upper border of the hyoid bone and supplies blood to the attached muscles.

Function

The hyoid bone sits above the thyroid cartilage. Larynx external en.svg
The hyoid bone sits above the thyroid cartilage.

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. [6] Its descent in living creatures is not unique to Homo sapiens , [7] 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 two-year-old babies. Moreover, the larynx position of Neanderthals was not a handicap to producing speech sounds. [8] 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. [9] However, other researchers have claimed that the morphology of the hyoid is not indicative of the larynx's position. Recent research has indicated that the hyoid bone may have significant involvement in the ability to swallow. It has been hypothesized that the mammalian hyoid bone evolved in conjunction with the development of lactation, thus allowing babies to suckle milk. [10] It is necessary to take into consideration the skull base, the mandible and the cervical vertebrae and a cranial reference plane. [11] [12]

Muscle attachments

A large number of muscles attach to the hyoid: [13]

Clinical significance

The hyoid bone is important to a number of physiological functions, including breathing, swallowing and speech. It is also thought to play a key role in keeping the upper airway open during sleep, [14] [15] and as such, the development and treatment of obstructive sleep apnea (OSA; characterized by repetitive collapse of the upper airway during sleep). A mechanistic involvement of the hyoid bone in OSA is supported by numerous studies demonstrating that a more inferiorly positioned hyoid bone is strongly associated with the presence and severity of the disorder. [16] [17] Movement of the hyoid bone is also thought to be important in modifying upper airway properties, which was recently demonstrated in computer model simulations. [18] A surgical procedure that aims to potentially increase and improve the airway is called hyoid suspension.

Due to its position, the hyoid bone is not easily susceptible to fracture. In a suspected case of murder or physical abuse of an adult, a fractured hyoid strongly indicates throttling or strangulation. In children and adolescents (in whom the hyoid bone is still flexible because ossification is yet to be completed) fracture may not occur even after serious trauma.

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 called the hyoid arch . In many vertebrates, 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. [19] The howler monkey Alouatta has a pneumatized hyoid bone, one of the few cases of postcranial pneumatization of bones outside Saurischia.

In mammals, the hyoid often determines whether one can roar. If the hyoid is incompletely ossified (for example: lions) it allows the animal to roar, but not purr. If the hyoid is completely ossified (for example: cheetahs), it does not allow the animal to roar, but instead will allow the animal to purr and meow, as seen in house cats (lions, cheetahs and house cats all belong to the family Felidae). [20]

In veterinary anatomy, the term hyoid apparatus is the collective term used to refer to the bones of the tongue—a pair of stylohyoidea, a pair of thyrohyoidea, and unpaired basihyoideum [21] —and associated, upper-gular connective tissues. [22] In humans, the single hyoid bone is an equivalent of the hyoid apparatus. [23]

See also

Related Research Articles

<span class="mw-page-title-main">Larynx</span> Voice box, an organ in the neck of amphibians, reptiles, and mammals

The larynx, commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about 4–5 centimeters in diameter. The larynx houses the vocal cords, and manipulates pitch and volume, which is essential for phonation. It is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The word ʻlarynxʼ comes from the Ancient Greek word lárunx ʻlarynx, gullet, throat.ʼ

Neck Part of the body on many vertebrates that connects the head with the torso

The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In addition, the neck is highly flexible and allows the head to turn and flex in all directions. The structures of the human neck are anatomically grouped into four compartments; vertebral, visceral and two vascular compartments. Within these compartments, the neck houses the cervical vertebrae and cervical part of the spinal cord, upper parts of the respiratory and digestive tracts, endocrine glands, nerves, arteries and veins. Muscles of the neck are described separately from the compartments. They bound the neck triangles.

Suprahyoid muscles

The suprahyoid muscles are four muscles located above the hyoid bone in the neck. They are the digastric, stylohyoid, geniohyoid, and mylohyoid muscles. They are all pharyngeal muscles, with the exception of the geniohyoid muscle. The digastric is uniquely named for its two bellies. Its posterior belly rises from the mastoid process of the cranium and slopes downward and forward. The anterior belly arises from the digastric fossa on the inner surface of the mandibular body, which slopes downward and backward. The two bellies connect at the intermediate tendon. The intermediate tendon passes through a connective tissue loop attached to the hyoid bone. The mylohyoid muscles are thin, flat muscles that form a sling inferior to the tongue supporting the floor of the mouth. The geniohyoids are short, narrow muscles that contact each other in the midline. The stylohyoids are long, thin muscles that are nearly parallel with the posterior belly of the digastric muscle.

Infrahyoid muscles

The infrahyoid muscles, or strap muscles, are a group of four pairs of muscles in the anterior (frontal) part of the neck. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles.

Omohyoid muscle

The omohyoid muscle is a muscle that depresses the hyoid. It is located in the front of the neck, and consists of two bellies separated by an intermediate tendon. The omohyoid muscle is proximally attached to the scapula and distally attached to the hyoid bone, stabilising it. Its superior belly serves as the most lateral member of the infrahyoid muscles, located lateral to both the sternothyroid muscles and the thyrohyoid muscles.

Digastric muscle Small muscle located under the jaw in mammals

The digastric muscle is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle bellies include the suspensory muscle of duodenum, omohyoid, occipitofrontalis.

Geniohyoid muscle Muscle

The geniohyoid muscle is a narrow muscle situated superior to the medial border of the mylohyoid muscle. It is named for its passage from the chin to the hyoid bone.

Sternothyroid muscle

The sternothyroid muscle, or sternothyroideus, is an infrahyoid muscle in the neck. It acts to depress the hyoid bone. It is below the sternohyoid muscle. It is shorter and wider than the sternohyoid.

Hyoglossus Muscle

The hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the styloglossus and the inferior longitudinal muscle of the tongue. It forms a part of the floor of submandibular triangle.

Middle pharyngeal constrictor muscle

The middle pharyngeal constrictor is a fan-shaped muscle located in the neck. It is one of three pharyngeal constrictors. Similarly to the superior and inferior pharyngeal constrictor muscles, the middle pharyngeal constrictor is innervated by a branch of the vagus nerve through the pharyngeal plexus. The middle pharyngeal constrictor is smaller than the inferior pharyngeal constrictor muscle.

Stylopharyngeus muscle

The stylopharyngeus is a muscle in the head that stretches between the temporal styloid process and the pharynx.

<span class="mw-page-title-main">Pharyngeal arch</span> Embryonic precursor structures in vertebrates

The pharyngeal arches, also known as visceral arches, are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arches.

Thyrohyoid membrane Fibroelastic sheet connecting the thyroid cartilage to the hyoid bone

The thyrohyoid membrane is a broad, fibro-elastic sheet of the larynx. It connects the upper border of the thyroid cartilage to the hyoid bone.

Superior thyroid artery

The superior thyroid artery arises from the external carotid artery just below the level of the greater cornu of the hyoid bone and ends in the thyroid gland.

Temporal styloid process

The temporal styloid process is a process of bone that extends down from the temporal bone of the human skull, just below the ear.

Deep cervical fascia

The deep cervical fascia lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its attachment to the hyoid bone prevents the formation of a dewlap.

Carotid triangle

The carotid triangle is a portion of the anterior triangle of the neck.

Cervical lymph nodes

Cervical lymph nodes are lymph nodes found in the neck. Of the 800 lymph nodes in the human body, 300 are in the neck. Cervical lymph nodes are subject to a number of different pathological conditions including tumours, infection and inflammation.

Outline of human anatomy Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

References

PD-icon.svgThis article incorporates text in the public domain from page 177 of the 20th edition of Gray's Anatomy (1918)

  1. hednk-023 —Embryo Images at University of North Carolina
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  17. Genta, PR; Schorr, F; Eckert, DJ; Gebrim, E; Kayamori, F; Moriya, HT; Malhotra, A; Lorenzi-Filho, G (1 October 2014). "Upper airway collapsibility is associated with obesity and hyoid position". Sleep. 37 (10): 1673–8. doi:10.5665/sleep.4078. PMC   4173923 . PMID   25197805.
  18. Amatoury, J; Cheng, S; Kairaitis, K; Wheatley, JR; Amis, TC; Bilston, LE (2016). "Development and validation of a computational finite element model of the rabbit upper airway: simulations of mandibular advancement and tracheal displacement". J Appl Physiol. 120 (7): 743–57. doi: 10.1152/japplphysiol.00820.2015 . PMID   26769952.
  19. Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. p. 214. ISBN   0-03-910284-X.
  20. SeaWorld https://seaworld.org/animals/all-about/cheetah/communication/
  21. Shoshani J., Marchant G.H. (2001.) Hyoid apparatus: a little-known complex of bones and its "contribution" to proboscidean evolution, The World of Elephants - International Congress, Rome, pp. 668–675.
  22. Klappenbach, Laura. "Hyoid Apparatus - Definition of Hyoid Apparatus". The New York Times Company. Archived from the original on 2012-01-20. Retrieved 2017-03-20.
  23. "hyoid apparatus - Definition". mondofacto.com. Archived from the original on 2011-11-08.