Hyoid bone
Overview
 
The hyoid bone (Latin os hyoideum) is a horseshoe-shaped bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

 situated in the anterior midline of the neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 between the chin
Chin
In the human anatomy, the chin is the lowermost part of the face.It is formed by the lower front of the mandible.People show a wide variety of chin structures. See Cleft chin....

 and the thyroid cartilage
Thyroid cartilage
The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx....

. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra 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.
Encyclopedia
The hyoid bone (Latin os hyoideum) is a horseshoe-shaped bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

 situated in the anterior midline of the neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 between the chin
Chin
In the human anatomy, the chin is the lowermost part of the face.It is formed by the lower front of the mandible.People show a wide variety of chin structures. See Cleft chin....

 and the thyroid cartilage
Thyroid cartilage
The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx....

. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra 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
Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...

 and pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...

 behind.

Its name is derived from the Greek word hyoeides meaning "shaped like the letter upsilon
Upsilon
Upsilon is the 20th letter of the Greek alphabet.  In the system of Greek numerals it has a value of 400. It is derived from the Phoenician waw. The name of the letter is pronounced in Modern Greek, and in English , , or...

" (υ).

Segments

The bone consists of a central part, called the body and two pairs of cornua, the greater cornu and the lesser cornu.
  • Body of hyoid
  • Greater cornu
    Greater cornu
    The greater cornua of the hyoid bone project backward from the lateral borders of the body; they are flattened from above downward and diminish in size from before backward; each ends in a tubercle to which is fixed the lateral hyothyroid ligament.The upper surface is rough close to its lateral...

     (2)
  • Lesser cornu
    Lesser cornu
    The lesser cornua are two small, conical eminences, attached by their bases to the angles of junction between the body and greater cornua of the hyoid bone....

     (2)

Embryology

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.

Ossification

The hyoid is ossified
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...

 from six centers: two for the body, and one for each cornu
Cornu
Cornu is a Latin word for horn.Cornu may also refer to:*Cornu , an ancient musical instrumentPeople:*Dominique Cornu, a Belgian road and track cyclist, born 1985....

. Ossification commences in the greater cornua toward the end of fetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 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:
Superior
  • Middle pharyngeal constrictor muscle
    Middle pharyngeal constrictor muscle
    The middle pharyngeal constrictor is a fanshaped muscle, smaller than the Inferior pharyngeal constrictor muscle.-Origin and insertion:It arises from the whole length of the upper border of the greater cornu of the hyoid bone, from the lesser cornu, and from the stylohyoid ligament.The fibers...

     
  • Hyoglossus muscle
  • Digastric muscle
    Digastric muscle
    The digastric muscle is a small muscle located under the jaw. so digastric muscles are muscle fibers in ligament of treitz ,omohyoid , occipitofrontalis....

  • Stylohyoid muscle
    Stylohyoid muscle
    The stylohyoid muscle is a slender muscle, lying anterior, and superior of the posterior belly of the digastric muscle. It shares this muscle's innervation by the facial nerve, and functions to draw the hyoid bone backwards and elevate the tongue....

  • Geniohyoid muscle
    Geniohyoid 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.-Origin and insertion:...

  • Mylohyoid muscle
    Mylohyoid muscle
    The mylohyoid muscle is a muscle running from the mandible to the hyoid bone, forming the floor of the oral cavity. It is named for its two attachments, with the prefix "mylo" coming from the Greek word for "molar". These muscles are mesodermal in origin...



Inferior
  • Thyrohyoid muscle
    Thyrohyoid muscle
    The Thyrohyoid muscle is a small, quadrilateral muscle appearing like an upward continuation of the Sternothyreoideus. It belongs to the infrahyoid muscles group....

  • Omohyoid muscle
    Omohyoid muscle
    The omohyoid muscle is a muscle at the front of the neck that consists of two bellies separated by an intermediate tendon. It belongs to the group of infrahyoid muscles...

  • Sternohyoid muscle
    Sternohyoid muscle
    The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum, one of the paired strap muscles of the infrahyoid muscles serving to depress the hyoid bone...



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. 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. The discovery of a modern-looking hyoid bone of a Neanderthal
Neanderthal
The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia...

 man in the Kebara Cave
Kebara Cave
Kebara Cave is an Israeli limestone cave locality of the Wadi Kebara, situated at 60 - 65 metres ASL on the western escarpment of the Carmel Range, some 10km north-east of Caesarea...

 in Palestine
Palestine
Palestine is a conventional name, among others, used to describe the geographic region between the Mediterranean Sea and the Jordan River, and various adjoining lands....

 led its discoverers to argue that the Neanderthals had a descended larynx
Larynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

, and thus human-like speech
Speech
Speech is the human faculty of speaking.It may also refer to:* Public speaking, the process of speaking to a group of people* Manner of articulation, how the body parts involved in making speech are manipulated...

 capabilities. However, other researchers have claimed that the morphology of the hyoid is not indicative of the larynx's position. It is necessary to take into consideration the skull base, the mandible and the cervical vertebrae and a cranial reference plane.

Fracture and applied anatomy

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. However this is not 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
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, which separates the first gill slit from the spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...

, 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. Amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s and reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s may have many cornua, while mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s (including humans) have two pairs, and bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s only one. In birds, and some reptiles, the body of the hyoid is greatly extended forward, creating a solid bony support for the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

. The howler monkey Alouatta has a pneumatized hyoid bone, one of the few cases of postcranial pneumatization of bones outside Saurischia
Saurischia
Saurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...

.

Additional images

See also

  • Adam's apple
    Adam's apple
    The laryngeal prominence—commonly known as the Adam's Apple—is a feature of the human neck. This lump, or protrusion, is formed by the angle of the thyroid cartilage surrounding the larynx...

  • Bone terminology
  • Terms for anatomical location

External links

- "Anterior Triangle of the Neck: The Muscular Triangle"
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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