Left posterior view into the posterior cranial fossa. The brainstem (towards the right) has been removed and this image shows the fibers of the glossopharyngeal, vagus, spinal accessory nerves approaching the jugular foramen. The hypoglossal nerve is descending toward the hypoglossal canal. The tympanic branch of the glossopharyngeal nerve (Jacobson's nerve) can be seen entering the tympanic canaliculus, a bony septum separating the openings of the carotid canal and jugular foramen, enroute to the middle ear cavity. It supplies sensory fibers to the mucosal lining of this cavity and parasympathetic fibers to the parotid gland via the lesser petrosal nerve. The auricular branch of the vagus nerve (Arnold's nerve) is shown coursing to the mastoid canaliculus along the lateral wall of the jugular fossa. It provides sensory innervation to a small posterior portion of the external auditory meatus. (Image courtesy of AL Rhoton, Jr.)