Overview
The tongue contains both intrinsic and extrinsic muscles that work together to control shape, position, articulation, swallowing, and airway protection. All intrinsic muscles and most extrinsic muscles are supplied by the hypoglossal nerve (CN XII), with one important exception: palatoglossus, which is innervated by the vagus nerve (CN X). This high-yield summary covers origins, insertions, actions, and nerve supply for each muscle group.
For regional orientation, see tongue anatomy and hypoglossal nerve.
Intrinsic Muscles of the Tongue
Intrinsic muscles change the shape of the tongue. They are fully contained within the tongue and have no bony attachments.
Intrinsic Muscle Summary
| Muscle | Orientation | Action | Nerve Supply |
|---|---|---|---|
| Superior Longitudinal | Runs along dorsum from base to apex | Curls tongue upward; shortens tongue | Hypoglossal nerve (CN XII) |
| Inferior Longitudinal | Runs along underside from root to apex | Curls tongue downward; shortens tongue | Hypoglossal nerve (CN XII) |
| Transverse | Runs from median septum to lateral margins | Narrows and elongates tongue | Hypoglossal nerve (CN XII) |
| Vertical | Runs from dorsal to ventral surface | Flattens and broadens tongue | Hypoglossal nerve (CN XII) |
Extrinsic Muscles of the Tongue
Extrinsic muscles position the tongue by connecting it to surrounding bones and soft tissues. They move the tongue up, down, forward, and backward.
Extrinsic Muscle Summary
| Muscle | Origin | Insertion | Action | Nerve Supply |
|---|---|---|---|---|
| Genioglossus | Superior mental spine (mandible) | Dorsum of tongue; hyoid body | Protrudes tongue; depresses central portion; prevents tongue collapse | Hypoglossal nerve (CN XII) |
| Hyoglossus | Body and greater horn of hyoid | Side of tongue | Depresses and retracts tongue | Hypoglossal nerve (CN XII) |
| Styloglossus | Styloid process (temporal bone) | Side of tongue | Retracts and elevates tongue; important in swallowing | Hypoglossal nerve (CN XII) |
| Palatoglossus | Palatine aponeurosis | Side of tongue | Elevates posterior tongue; closes oropharyngeal isthmus | Vagus nerve (CN X) via pharyngeal plexus |
Nerve Supply Summary
| Region / Muscle Group | Nerve | Notes |
|---|---|---|
| Intrinsic muscles | Hypoglossal nerve (CN XII) | All intrinsic muscles share the same motor supply. |
| Extrinsic muscles (except one) | Hypoglossal nerve (CN XII) | Genioglossus, hyoglossus, styloglossus. |
| Palatoglossus | Vagus nerve (CN X) | Only tongue muscle not supplied by CN XII. |
Functional Summary
- Protrusion: Genioglossus (main).
- Retraction: Styloglossus + hyoglossus.
- Elevation: Styloglossus; palatoglossus (posterior tongue).
- Depression: Hyoglossus; genioglossus (central portion).
- Shape changes: All intrinsic muscles.
Clinical Correlations
Understanding tongue muscle innervation is particularly important in neurological examination and airway evaluation.
- Hypoglossal nerve lesion: Tongue deviates toward the side of the lesion on protrusion due to unopposed action of genioglossus of the normal side.
- CN X lesion: Palatoglossus dysfunction may impair elevation of posterior tongue and closure of oropharyngeal isthmus.
- Sleep apnea relevance: Weakness of genioglossus predisposes to posterior tongue collapse.
- Dysarthria and dysphagia: Often reflect combined intrinsic and extrinsic muscle impairment.
For expanded anatomical context, review tongue anatomy and hypoglossal nerve pathway.