Genioglossus muscle

The genioglossus is the largest and most powerful extrinsic muscle of the tongue. It is a flat triangular muscle that forms the bulk of the tongue’s body and is chiefly responsible for protruding the tongue and maintaining airway patency (preventing tongue fall-back).

Anatomical Details

1. Origin

From the superior mental (genial) spine on the inner surface of the mandibular symphysis.

2. Insertion

Fibres fan out posteriorly and superiorly, such that:

• The inferior fibres insert into the body of hyoid bone

• The middle fibres pass backward

• The superior fibres extend backward and forward to insert into the entire dorsum of the tongue (from the root to the tip).

Nerve Supply

Hypoglossal nerve (cranial nerve XII).

Blood Supply

• Lingual artery (branch of the external carotid artery).

• Submental branch of facial artery

Actions

• Protrudes the tongue.

• Unilateral contraction draws the tongue toward the opposite side.

• The genioglossus is active even during rest to keep the airway open, especially during sleep. Dysfunction or hypotonia (e.g., in sleep apnoea) can contribute to airway collapse.

Clinical Correlation

• In hypoglossal nerve lesions, the tongue deviates toward the affected side on protrusion due to unopposed action of the contralateral genioglossus.

• Atrophy and fasciculations may be seen on the same side in lower motor neuron lesions.