Genioglossus muscle

At a glance

English

Genioglossus muscle

Latin (TA2)

Musculus genioglossus

System

Muscle

Region

Head

Side

Paired, left and right

About the genioglossus muscle

The genioglossus is the largest of the extrinsic tongue muscles, the group that attaches the tongue to bone and moves it as a whole. It lies on each side of the midline, separated from its partner by a thin fibrous septum, and makes up the bulk of the tongue's body. Its shape is a fan, with the handle at the chin and the blades spreading up and back through the whole length of the tongue.

It arises by a short tendon from the upper mental spine, a small projection on the inner surface of the mandible behind the symphysis, just above the origin of geniohyoid. From there its fibres fan out. The lowest pass back to the front of the body of the hyoid bone; the middle ones run back into the root of the tongue; and the upper ones curve forwards and up to the tip. All end on the underside of the tongue's lining and in its connective tissue, from root to apex.

Its key action is protrusion: the lower and back fibres pull the root of the tongue forwards, so the tip is pushed out of the mouth. When one side acts more than the other, the tongue goes forwards and towards the opposite side. Acting together, the two muscles also depress the middle of the tongue, making a groove along its upper surface, while the front fibres can draw the tip back. Like all tongue muscles apart from palatoglossus, it is supplied by the hypoglossal nerve, and its blood comes from the sublingual and deep lingual branches of the lingual artery.

Because it holds the tongue forward, the genioglossus keeps open the narrowest and most collapsible part of the upper airway behind the tongue. Its tone falls in sleep, especially in dream sleep, and loss of that tone contributes to obstructive sleep apnoea. Under anaesthesia the same problem is managed by lifting the jaw forwards, which pulls the tongue with it. Asking a patient to put out the tongue tests the hypoglossal nerve: after damage to one nerve, the tongue points towards the weak side.

Attachments, action and supply

Origin

Superior mental spine on the inner surface of the mandibular symphysis.

Insertion

Whole length of the underside of the tongue, from root to tip, and the front of the body of the hyoid bone.

Action

Protrudes the tongue; one side turns it towards the opposite side; together they depress and groove the middle of the tongue.

Nerve supply

Hypoglossal nerve (cranial nerve XII).

Blood supply

Sublingual and deep lingual branches of the lingual artery, from the external carotid artery.