Genioglossus (Inferior Fibers)
Tongue · Head & Neck
The genioglossus is the large fan-shaped extrinsic muscle that forms the bulk of the tongue, arising from the superior genial tubercle (mental spine) on the inner surface of the mandible and radiating back into the dorsum of the tongue and the body of the hyoid bone. Its inferior fibres, the lowest part of the fan, run most horizontally toward the hyoid and are the ones responsible for drawing the tongue forward, that is, protruding it. Because both genioglossi pull the tongue toward the midline as they protrude it, weakness on one side lets the tongue deviate toward the paralysed side on protrusion, a classic clinical sign. Like all the extrinsic and intrinsic tongue muscles except palatoglossus, it is supplied by the hypoglossal nerve (CN XII).
Origin, Insertion, Action & Nerve
Origin
Superior genial tubercle (mental spine) of the mandible
Insertion
Dorsum of the tongue and body of the hyoid bone
Action
Protrudes the tongue (draws it forward)
Nerve
Hypoglossal nerve (CN XII)
Attachments explained
The Genioglossus (Inferior Fibers) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Superior genial tubercle (mental spine) of the mandible
Insertion
Dorsum of the tongue and body of the hyoid bone
Action & function
When the Genioglossus (Inferior Fibers) contracts, it produces the following movement: Protrudes the tongue (draws it forward).
As part of the Tongue group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Genioglossus (Inferior Fibers) receives its nerve supply from the Hypoglossal nerve (CN XII).
Because a muscle can only contract when its nerve is intact, injury to the Hypoglossal nerve can weaken or paralyse the Genioglossus (Inferior Fibers), impairing the movements it normally produces (protrudes the tongue (draws it forward)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Genioglossus (Inferior Fibers) (the OIANS method)
Fix the inferior fibres as the protruders of the tongue. Picture the fan of genioglossus anchored at the chin, with its lowest, most forward-directed fibres pulling the tongue straight out of the mouth. Saying protrusion equals inferior genioglossus links the specific fibre group to its single most testable action.
Tie the muscle to its clinical test to lock in the nerve. Because genioglossus protrudes the tongue and both sides converge on the midline, a hypoglossal (CN XII) lesion causes the protruded tongue to point toward the weak side. If you can explain that deviation, you already hold the origin at the mental spine, the action of protrusion, and the nerve together.
Frequently asked questions
Where is the Genioglossus (Inferior Fibers) located?
The Genioglossus (Inferior Fibers) is a muscle of the Tongue group, located in the Head & Neck.
What is the origin of the Genioglossus (Inferior Fibers)?
Superior genial tubercle (mental spine) of the mandible
What is the insertion of the Genioglossus (Inferior Fibers)?
Dorsum of the tongue and body of the hyoid bone
What movements does the Genioglossus (Inferior Fibers) produce?
Protrudes the tongue (draws it forward)
What nerve supplies the Genioglossus (Inferior Fibers)?
Hypoglossal nerve (CN XII)
Is the Genioglossus (Inferior Fibers) free to study in OIANS?
The Genioglossus (Inferior Fibers) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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