Vestibular aqueduct

The vestibular aqueduct (vestibular canaliculus) is a narrow bony canal which emerges from the bony vestibule. It traverses backwards through the temporal bone and eventually open up onto the posterior surface of the petrous part of the temporal bone, into the posterior cranial fossa.

The vestibular aqueduct of the bony labyrinth hosts within it, a ductus endolymphaticus (endolymphatic duct and sac). The latter is part of the membranous labyrinth and contains a fluid called endolymph, while the space between ductus endolymphaticus and vestibular aqueduct is filled up by perilymph. Since, endolymphatic duct and sac tightly plug in the vestibular aqueduct, therefore, no fluid leaks out from it into the posterior cranial fossa.

Note: the term vestibular canaliculus is preferred term when the morphology of the temporal bone is considered; the term vestibular aqueduct is used when the internal ear is the focus of study.