The superior longitudinal muscle is one of four intrinsic tongue muscles (with the inferior longitudinal, transverse, and vertical). It runs as a layer of oblique and longitudinal fibres immediately beneath the dorsal mucosa from root to tip. Contraction shortens the tongue and turns the tip upward, contributing to the complex repertoire of tongue shaping required for speech and swallowing.
| Origin | Submucous fibrous layer at the tongue root and median fibrous septum |
|---|---|
| Insertion | Tongue tip and lateral margins of the tongue |
| Nerve Supply | Hypoglossal nerve (CN XII) |
| Blood Supply | Lingual artery (dorsal lingual branches) |
| Actions | Shortens the tongue; Curls the tongue tip upward and retracts it |
|---|
The intrinsic tongue muscles are assessed as a group through CN XII function testing: tongue protrusion, retraction, lateral movement, and shaping. In hypoglossal nerve palsy, all ipsilateral intrinsic muscles atrophy and the tongue deviates toward the affected side on protrusion. Electromyography of the tongue intrinsics samples these muscles to assess XII lesions. In reconstructive tongue surgery, intrinsic muscle preservation or reconstruction determines functional outcome for speech and swallowing.
Not directly palpable individually; assessed as part of overall tongue mobility.
CN XII injury from skull base tumour, carotid endarterectomy, or neck dissection causes ipsilateral tongue atrophy and deviation on protrusion due to paralysis of all intrinsic and most extrinsic tongue muscles on the affected side.
