Section 181: The tympanic segment (VIId) of the facial nerve is about to reach the posterior wall of the middle ear space to form the pyramidal bend. Note that there is a dehiscence (arrow) in the bony facial canal so that there is only a thin connective tissue covering between the nerve and the middle ear space. The footplate of the stapes (fp) is held in the oval window by the annular ligament. The origin of the endolymphatic duct (ed) is visible at the origin of the vestibular aqueduct. c - Cochlea; ct - Chorda tympani.