Anatomy & Histology · single question
Which nerve, when blocked/damaged, does NOT cause problems with UPPER LIP ELEVATION?
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Correct answer: B. Nerve in the infraorbital canal (CN V2/infraorbital nerve) — does NOT cause upper lip MOTOR problems
✓ B) Infraorbital canal (CN V2) blockade does NOT cause upper lip ELEVATION problems.
Upper lip elevation is a MOTOR function controlled by CN VII (facial nerve) branches, specifically zygomatic and buccal branches (zygomaticus major/minor, levator labii superioris). CN V2/infraorbital nerve is a SENSORY nerve — it provides sensation to upper lip, lower eyelid, lateral nose, but NO motor function to lip elevators. Therefore: CN V2/infraorbital block → upper lip numbness/anesthesia (sensory) but lip movement is preserved. Blocking/damaging CN VII branches (stylomastoid foramen, parotid, labial vestibule) → motor paralysis of lip elevators.
Upper lip elevation is a MOTOR function controlled by CN VII (facial nerve) branches, specifically zygomatic and buccal branches (zygomaticus major/minor, levator labii superioris). CN V2/infraorbital nerve is a SENSORY nerve — it provides sensation to upper lip, lower eyelid, lateral nose, but NO motor function to lip elevators. Therefore: CN V2/infraorbital block → upper lip numbness/anesthesia (sensory) but lip movement is preserved. Blocking/damaging CN VII branches (stylomastoid foramen, parotid, labial vestibule) → motor paralysis of lip elevators.
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