Bony labyrinth (Latin)

The labyrinthus osseus is located within the pars petrosa ossis temporalis. It consists of three continuous parts: vestibulum, cochlea and canales semicirculares.The vestibulum is a central bony cavity which communicates with the auris media through the fenestra vestibuli on its lateral wall. Posterosuperiorly, the vestibule is continued by the three bony canales semicirculares, each placed in a specific anatomical plane. The canalis semicircularis anterior lies in the sagittal plane, the canalis posterior is in the lateral plane, while the canalis lateralis lies in the transverse plane. The canals arise from the vestibule via bony ampullae (anterior, posterior, lateral). They curve through their respective planes, diving back into the bony vestibulum. The canalis lateralis does so directly, while the canales anterior and posterior merge forming the crus osseum commune which then joins the vestibulum.The cochlea is a snail-like structure that spirals from the anterior part of the vestibulum. The cochlea is essentially a bony canal that spirals around its axis two and a half times. The central portion of the cochlea, i.e. the axis, around which it spirals is called the modiolus. Along the entire length of the cochlea is a thin bony lamina which divides the cochlea into two parts: scala vestibuli and scala tympani. These sub-canals are entirely separate except at the apex of the cochlea, where they communicate through a narrow slit called the helicotrema.The whole labyrinthus osseus is filled with perilymph.