Figure 23. Cranial Nerve VII - Facial Nerve
The chorda tympani carries special sensory fibers from taste buds in the anterior 1/3 of the tongue and presynaptic parasympathetic fibers to the sublingual and submandibular glands along with the minor salivary glands. It separates from the main trunk of the facial nerve just before the latter passes out of the temporal bone through the stylomastoid foramen. The chorda tympani, however, travels anteriorly into the middle ear. The nerve gets its name from its passage across the internal surface of the tympanic membrane colloquially known as the ear drum. At the anterior edge it leaves the temporal bone through the petrotympanic fissure into the infratemporal fossa. At this point it associates itself with the lingual nerve which as mentioned earlier is a branch of the mandibular nerve. The parasympathetic fibers will synapse in the submandibular ganglia and the post-ganglionic fibers will follow the lingual nerve to the submandibular and sublingual salivary glands. The sensory fibers do not synapse but are directly attached to the taste buds in the fungiform and foliate papillae.