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AN39.1-2 | Tongue — Gate Quiz
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Which nerve supplies the genioglossus muscle?
Correct! The hypoglossal nerve (CN XII) supplies all intrinsic and extrinsic tongue muscles except palatoglossus (which is supplied by CN X via the pharyngeal plexus). Genioglossus is the primary protruder of the tongue.
Hypoglossal nerve (CN XII) supplies all tongue muscles EXCEPT palatoglossus (CN X). Genioglossus protrudes the tongue. In CN XII palsy, the genioglossus is paralysed on the affected side and the tongue deviates toward the weak (affected) side on protrusion.
Incorrect. All tongue muscles except palatoglossus are supplied by CN XII (hypoglossal). Palatoglossus is the exception — it is supplied by CN X.
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Taste sensation from the anterior two-thirds of the tongue is carried by:
Correct! Taste from the anterior 2/3 of the tongue is carried by the chorda tympani (a branch of CN VII — facial nerve). The chorda tympani joins the lingual nerve (CN V3) in the infratemporal fossa and travels with it to the tongue.
Anterior 2/3 tongue: General sensory = CN V3 (lingual nerve); Taste = CN VII (chorda tympani). Posterior 1/3 tongue: Both general sensory and taste = CN IX (glossopharyngeal). A lesion isolating taste loss on anterior 2/3 indicates chorda tympani damage, not lingual nerve damage.
Incorrect. Taste from anterior 2/3 = CN VII (chorda tympani). The lingual nerve (CN V3) carries GENERAL sensation (touch, pain, temperature) — not taste.
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Cancer at the tip of the tongue is particularly dangerous because its lymphatic drainage is to:
Correct! The tip of the tongue drains bilaterally — first to the submental nodes (bilateral) and then to the bilateral deep cervical nodes. This bilateral drainage means that even a small midline cancer of the tongue tip requires bilateral neck dissection, unlike lateral tongue cancers which drain predominantly ipsilaterally.
Tongue lymphatic drainage: Tip → bilateral submental nodes → bilateral deep cervical. Lateral borders → ipsilateral submandibular → ipsilateral deep cervical (II-III). Posterior 1/3 → directly bilateral deep cervical. The bilateral risk at the tongue tip means any tip carcinoma needs bilateral neck management.
Incorrect. The tongue tip has BILATERAL lymphatic drainage to submental and deep cervical nodes — not just ipsilateral. This is why tongue tip cancers have a poor prognosis and require bilateral neck dissection.
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A patient with a nasopharyngeal carcinoma invading the skull base has right hypoglossal nerve palsy. On protruding the tongue, it will deviate to:
Correct! The tongue deviates toward the side of the lesion (the right, in this case). The intact left genioglossus muscle protrudes its half of the tongue forward, while the paralysed right genioglossus cannot contract — causing the tongue to fall to the weak (right) side.
In CN XII palsy: tongue deviates TOWARD the LESION side. The healthy genioglossus protrudes its half; the paralysed side cannot — the tongue swings toward the weak side. Memory: "falls toward the weak side." Also note ipsilateral tongue wasting and dysarthria (lingual consonants affected).
Incorrect. The tongue DEVIATES TOWARD the affected (weak) side. The healthy genioglossus wins — it protrudes its side forward and the paralysed side lags behind, pushing the tongue toward the paralysis.
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The anterior two-thirds of the tongue develops from the first pharyngeal arch. This embryological origin explains why its general sensory nerve supply is:
Correct! The mandibular nerve (CN V3) is the nerve of the first pharyngeal arch. Since the anterior 2/3 of the tongue develops from first arch structures (two lingual swellings + tuberculum impar), it retains its general sensory supply from CN V3 (lingual nerve — a branch of the mandibular nerve).
Pharyngeal arch nerves: 1st = CN V; 2nd = CN VII; 3rd = CN IX; 4th = CN X (superior laryngeal); 6th = CN X (recurrent laryngeal). This explains nerve supplies of tongue: anterior 2/3 (1st arch) = general sensory CN V3; taste = CN VII (chorda tympani accompanies); posterior 1/3 (3rd arch) = CN IX.
Incorrect. The nerve of the first pharyngeal arch is CN V (trigeminal), specifically the mandibular division (V3). This explains why general sensory from the anterior 2/3 tongue = CN V3 (lingual nerve).
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The lingual artery, primary blood supply to the tongue, is a branch of:
Correct! The lingual artery is a branch of the external carotid artery — it is the second branch of the external carotid (arising just above the superior thyroid artery). It enters the tongue between the hyoglossus and genioglossus muscles and gives the deep lingual artery to the tongue tip.
External carotid artery branches (mnemonic: Some Anatomists Love Face And Posterior Medial Supply): Superior thyroid, Ascending pharyngeal, Lingual, Facial, Occipital, Posterior auricular, Medial — then terminal: Superficial temporal + Maxillary. Lingual = 2nd anterior branch.
Incorrect. The lingual artery is a direct branch of the external carotid artery. Remember the branches of the external carotid: Superior thyroid → Lingual → Facial → (posterior group) → (terminal) superficial temporal + maxillary.
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A 22-year-old patient in a dental college in Pondicherry reports loss of taste on the left side of the anterior tongue and numbness of the left floor of the mouth after surgical extraction of the lower left third molar. The nerve injured is most likely:
Correct! Injury to the left lingual nerve PROXIMAL to where the chorda tympani joins it causes both loss of general sensation (touch, pain, temperature) AND loss of taste on the anterior 2/3 of the left tongue. If the chorda tympani alone were injured, only taste would be lost, not general sensation.
The lingual nerve (CN V3) runs immediately medial to the lower 3rd molar. The chorda tympani (CN VII, taste) joins the lingual nerve in the infratemporal fossa, proximal to the third molar. Injury at the molar = loss of BOTH general sensation (lingual nerve) AND taste (chorda tympani hitchhiking on the lingual nerve).
Incorrect. The combined loss of general sensation AND taste on the anterior 2/3 indicates injury to the LINGUAL NERVE proximal to the chorda tympani junction — not just the chorda tympani alone.
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In a patient with a right hypoglossal nerve palsy due to a penetrating neck injury, which finding would you expect on tongue examination?
Correct! Wasting (atrophy) occurs on the IPSILATERAL side — the side of the nerve lesion. A right hypoglossal nerve palsy causes denervation of the right side of the tongue (all intrinsic and extrinsic muscles on the right) → progressive wasting and wrinkling of the right hemitongue. The tongue also deviates to the right on protrusion.
CN XII palsy signs: (1) Tongue deviates to the AFFECTED side on protrusion. (2) Wasting (atrophy + wrinkling) of the IPSILATERAL hemitongue. (3) Dysarthria — difficulty with lingual consonants (L, N, T, D). (4) Dysphagia. Combined with wasting, this indicates a lower motor neuron CN XII lesion.
Incorrect. Wasting is IPSILATERAL to the nerve lesion. Right CN XII palsy → right tongue wasting. On protrusion, the tongue deviates to the right (toward the weak side).
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The palatoglossus muscle forms the anterior pillar of the fauces (palatoglossal fold). Unlike other tongue muscles, it is supplied by:
Correct! Palatoglossus is the ONLY tongue muscle supplied by the vagus nerve (CN X) via the pharyngeal plexus. This is because palatoglossus is embryologically derived from pharyngeal musculature — it functions more as a palatal muscle than a tongue muscle.
Rule: All tongue muscles are supplied by CN XII EXCEPT palatoglossus (CN X via pharyngeal plexus). Palatoglossus elevates the posterior tongue and closes the oropharyngeal isthmus. During swallowing, it prevents food from going back into the oral cavity. Note: in CN XII palsy, palatoglossus function is preserved.
Incorrect. Palatoglossus is NOT supplied by CN XII. It is the single exception to the rule — it is supplied by CN X (vagus) via the pharyngeal plexus.
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In Ludwig's angina, a life-threatening cellulitis of the floor of the mouth, infection spreads from the lower second molar periapical abscess. The muscle whose superior surface defines the sublingual space (and whose inferior surface is the submandibular space) is:
Correct! The mylohyoid muscle is the muscular floor of the oral cavity and is the key anatomical boundary between the sublingual space (above) and the submandibular space (below). In Ludwig's angina, infection spreads between these spaces via the posterior free border of mylohyoid.
Mylohyoid = muscular floor of the mouth. Above = sublingual space (contains sublingual gland, lingual nerve, hypoglossal nerve, sublingual vessels). Below = submandibular space (submandibular gland, facial artery). Ludwig's angina spreads rapidly: sublingual → submandibular → parapharyngeal → retropharyngeal → mediastinum (descending necrotizing mediastinitis — life-threatening).
Incorrect. The mylohyoid forms the floor of the oral cavity and separates the sublingual and submandibular spaces. Infection spreading between these two spaces is the hallmark of Ludwig's angina.
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