Expansion
Front Chorda, Back Glosso
Mnemonic
Two modalities, three nerves, and they split differently:
| Region | Taste | General sensation |
|---|---|---|
| Anterior two thirds | VII, chorda tympani | V3, lingual nerve |
| Posterior third | IX | IX |
| Epiglottis and root | X | X |
“The front splits, the back does not.” The anterior tongue takes taste from one nerve and touch from another; the posterior third takes both from the glossopharyngeal.
The split has an anatomical reason: the anterior two thirds derive from the first arch (hence V3 for sensation), but the taste fibres of the second arch nerve (VII) hitch a ride along the lingual nerve as the chorda tympani.
That is why damage to the chorda tympani in middle ear surgery causes loss of taste without any numbness, and why a lesion of the lingual nerve at the third molar causes numbness and taste loss, since the chorda tympani travels with it distally.
Expansion
- Anterior two thirds taste - chorda tympani, branch of CN VII
- Posterior one third taste and sensation - CN IX