Anatomy & Histology · patient case question
Which nerve carries the parasympathetic secretomotor supply to the SUBMANDIBULAR gland?
Patient case: Three tongues and a salivary gland
Patient: Three separate patients
Chief Complaint: A: reduced salivation on one side after surgery in the floor of the mouth. B: “My tongue has cracks in it — is something wrong?” C: “The red patches on my tongue keep moving around.”
Background: A, 55-year-old male: recent excision of a floor-of-mouth lesion. B, 46-year-old female: asymptomatic, noticed the appearance for years. C, 33-year-old male: mild sensitivity to acidic and spicy food; history of psoriasis.
Findings: B: deep grooves radiating across the dorsum of the tongue, no induration, no ulceration. C: well-demarcated red depapillated patches with raised white serpiginous borders, in different locations from those photographed at a visit three weeks ago.
Show answer and explanation
Correct answer: C. The chorda tympani branch of the facial nerve
- A. The LINGUAL NERVE is the CARRIER of these fibres for the final part of their course, but they are not its own. The lingual nerve's own function is general sensation — touch, temperature and pain — from the anterior two-thirds of the tongue.
- B. The hypoglossal nerve is purely MOTOR to the intrinsic and most extrinsic tongue muscles. It carries no secretomotor, sensory or gustatory fibres.
- C. CORRECT. Secretomotor fibres to the SUBMANDIBULAR and SUBLINGUAL glands arise in the superior salivatory nucleus and travel in the CHORDA TYMPANI, a branch of the FACIAL NERVE (CN VII). The chorda tympani joins the LINGUAL NERVE in the infratemporal fossa, and the fibres synapse in the SUBMANDIBULAR GANGLION, which is suspended from the lingual nerve, before reaching the glands. So the answer to ‘which nerve innervates the submandibular gland’ is the facial nerve, delivered by way of the lingual.
- D. That describes the PAROTID pathway, which is the classic point of confusion. CN IX supplies the parotid by way of the lesser petrosal nerve and the OTIC ganglion, with the auriculotemporal nerve as the final carrier.
Note: The chorda tympani carries TASTE from the anterior two-thirds of the tongue as well as these secretomotor fibres. That dual cargo explains why a LINGUAL NERVE injury during third molar surgery can cost the patient both sensation and taste on that side — and, in principle, salivary secretion too. Keep the two salivary pathways paired in memory: CN VII → chorda tympani → submandibular ganglion → submandibular and sublingual; CN IX → lesser petrosal → otic ganglion → parotid.
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