Which nerve provides innervation to the external surface of the tympanic membrane?

Which nerve provides innervation to the external surface of the tympanic membrane?

• A. Glossopharyngeal nerve
• B. Auriculotemporal nerve
• C. Vagus nerve
• D. Facial nerve

Answer: (B)

The key idea is how sensory nerves supply the two faces of the tympanic membrane. The external (lateral) surface gets innervation from the auriculotemporal nerve, a branch of the mandibular division of the trigeminal nerve. This explains why sensations from the outer ear and the tympanic membrane can be felt in regions served by V3, such as the temple and the side of the head. In contrast, the internal (medial) surface is innervated by the tympanic branches of the glossopharyngeal nerve via the tympanic plexus, which is why middle-ear pain can refer to the pharynx. The vagus contributes mainly to sensation in parts of the external auditory canal but not to the tympanic membrane’s external surface, and the facial nerve is primarily motor to the middle ear muscles rather than providing sensory innervation to the tympanic membrane. Therefore, the nerve supplying the external surface is the auriculotemporal nerve.

The key idea is how sensory nerves supply the two faces of the tympanic membrane. The external (lateral) surface gets innervation from the auriculotemporal nerve, a branch of the mandibular division of the trigeminal nerve. This explains why sensations from the outer ear and the tympanic membrane can be felt in regions served by V3, such as the temple and the side of the head.

In contrast, the internal (medial) surface is innervated by the tympanic branches of the glossopharyngeal nerve via the tympanic plexus, which is why middle-ear pain can refer to the pharynx. The vagus contributes mainly to sensation in parts of the external auditory canal but not to the tympanic membrane’s external surface, and the facial nerve is primarily motor to the middle ear muscles rather than providing sensory innervation to the tympanic membrane. Therefore, the nerve supplying the external surface is the auriculotemporal nerve.