From the posterior wall of the saccule a canal, the endolymphatic duct, is given off; this duct is joined by the ductus utriculosaccularis, and then passes along the aquaeductus vestibuli and ends in a blind pouch (endolymphatic sac) on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater.
The membranous labyrinth. (Ductus endolymphaticus labeled at bottom center.)
Endolymphatic duct is #6, and is labeled at top center.
Disorders of the endolymphatic duct include Meniere's Disease and Enlarged Vestibular Aquduct.