Which cranial nerve is responsible for sensory input from the tympanic membrane?

The glossopharyngeal nerve plays a crucial role in conveying sensory information from various structures, including the tympanic membrane (eardrum). It is responsible for providing sensory innervation to the oropharynx and the posterior third of the tongue, as well as the middle ear, where the tympanic membrane is located. Specifically, the sensory fibers of the glossopharyngeal nerve carry sensations of touch, pain, and temperature, allowing for a rich understanding of the state of the tympanic membrane and surrounding areas.

The facial nerve primarily serves motor functions, including the control of facial expressions, as well as some sensory innervation related to taste from the anterior two-thirds of the tongue. The trigeminal nerve is mainly responsible for sensory sensations from the face, including the forehead, cheeks, and jaw, but does not directly provide sensory input from the tympanic membrane. The hypoglossal nerve is mainly a motor nerve that controls the muscles of the tongue and does not have sensory components related to the tympanic membrane or the ear.

Thus, the glossopharyngeal nerve is the definitive choice for this role, as its sensory fibers are specifically involved with the tympanic membrane's sensory input.