The geniohyoid muscle is a narrow paired

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

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 Human mandible, mandible to the hyoid bone, forming the floor of the oral cavity of the human mouth, mouth. It is named after its two attachments near the mo ...

. It is named for its passage from the

chin The chin is the forward pointed part of the anterior mandible (List_of_human_anatomical_regions#Regions, 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 we ...

("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 verte ...

Structure

The geniohyoid is a paired short muscle that 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 ha ...

, and runs backward and slightly downward, to be inserted into the anterior surface of the body of the

. 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 digastr ...

. The muscle receives its blood supply from branches of the lingual artery.

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 b ...

. Although the first three cervical nerves give rise to the

ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop formed by muscular branches of the cervical plexus formed by branches of cervical spinal nerves C1-C3. The ansa cervicalis has two roots - a superior root (formed by branch o ...

, 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 of hyoid bone and genioglossus occur.

Function

The geniohyoid muscle brings the

forward and upwards. This dilates the upper airway, assisting respiration. 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 ( ; ''Homo neanderthalensis'' or sometimes ''H. sapiens neanderthalensis'') are an extinction, extinct group of archaic humans who inhabited Europe and Western and Central Asia during the Middle Pleistocene, Middle to Late Plei ...

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

References

External links

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