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The geniohyoid muscle is a narrow
muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...
situated superior to the medial border of the
mylohyoid muscle The mylohyoid muscle or diaphragma oris is a paired muscle of the neck. It runs from the mandible to the hyoid bone, forming the floor of the oral cavity of the mouth. It is named after its two attachments near the molar teeth. It forms the flo ...
. It is named for its passage from the
chin The chin is the forward pointed part of the anterior mandible ( mental region) below the lower lip. A fully developed human skull has a chin of between 0.7 cm and 1.1 cm. Evolution The presence of a well-developed chin is considered to be one ...
("genio-" is a standard prefix for "chin") to the
hyoid bone The hyoid bone (lingual bone or tongue-bone) () 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 verteb ...
.


Structure

It arises from the inferior
mental spine A mental spine is a small projection of bone on the posterior aspect of the mandible in the midline. There are usually four mental spines: two superior and two inferior. Collectively they are also known as the ''genial tubercle'',"Genial tubercle. ...
, on the back of the
mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halve ...
, and runs backward and slightly downward, to be inserted into the anterior surface of the body of the
hyoid bone The hyoid bone (lingual bone or tongue-bone) () 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 verteb ...
. It lies in contact with its fellow of the opposite side. It thus belongs to the
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 ...
. The muscle is supplied by branches of the
lingual artery The lingual artery arises from the external carotid artery between the superior thyroid artery and facial artery. It can be located easily in the tongue. Structure The lingual artery first branches off from the external carotid artery. It runs ...
.


Innervation

The geniohyoid muscle is innervated by fibres from the first cervical spinal nerve travelling alongside the
hypoglossal nerve The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated ...
. Although the first three cervical nerves give rise to the
ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin. Bra ...
, the geniohyoid muscle is said to be innervated by the first cervical nerve, as some of its efferent fibers do not contribute to ansa cervicalis.


Variations

It may be blended with the one on opposite side or double; slips to
greater cornu The hyoid bone (lingual bone or tongue-bone) () 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 ...
of hyoid bone and
genioglossus The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue. Structure Genioglossus is the fan-shaped extrinsic tongue muscle that forms the ma ...
occur.


Function

The geniohyoid muscle brings the
hyoid bone The hyoid bone (lingual bone or tongue-bone) () 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 verteb ...
forward and upwards. This dilates the
upper airway The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose to th ...
, assisting
respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...
. During the first act of deglutition, when the mass of food is being driven from the mouth into the pharynx, the hyoid bone, and with it the tongue, is carried upward and forward by the anterior bellies of the Digastrici, the Mylohyoidei, and Geniohyoidei. It also assists in depressing the mandible


History

The inclined position of the geniohyoid muscle has been contrasted to the horizontal position in
neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an Extinction, extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ag ...
s.


Additional images

File:Gray186.png, Illustration of the hyoid bone showing the insertion point of the geniohyoid muscle File:Gray994.png, Sagittal section of nose mouth, pharynx, and larynx. File:Slide1ss.JPG, Geniohyoid muscle File:Slide4ss.JPG, Geniohyoid muscle File:Slide9ss.JPG, Geniohyoid muscle


See also


References


External links

* *
Frontal section
{{Authority control Muscles of the head and neck Suprahyoid muscles