Which nerve provides sensory innervation to the internal surface of the tympanic membrane?

• A. Glossopharyngeal nerve
• B. Trigeminal nerve V2
• C. Facial nerve
• D. Vagus nerve

Answer: (A)

The inner (medial) surface of the tympanic membrane gets its sensory supply from the glossopharyngeal nerve through its tympanic branch (Jacobson’s nerve). This tympanic nerve enters the middle ear via the tympanic canaliculus, forms the tympanic plexus on the promontory, and then provides sensory fibers to the mucosa of the middle ear and the internal surface of the tympanic membrane. The other nerves listed do not innervate this inner surface in a general sense—their roles are elsewhere (for example, the outer surface is supplied by branches from the trigeminal system, while the facial and vagus nerves have other sensory or motor roles in the ear area).