Right posterior view into the posterior cranial fossa. The lateral surface of the medulla on the upper left border of the image shows emerging fibers of the glossopharyngeal, vagus, spinal accessory (all approaching the jugular foramen), and hypoglossal nerves (shown traversing the hypoglossal canal, which has been opened). The vertebral artery courses lateral to the medulla. 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.)