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Bony labyrinth

The bony labyrinth (or osseous labyrinth, otic capsule, Latin: labyrinthus osseus) is a bony capsule that consists of a complex system of interconnected cavities and canals in the internal ear that enclose the membranous labyrinth. The bony labyrinth is composed of three parts:

  • Vestibule
  • Semicircular canals (3)
  • Cochlea

The bony labyrinth is located in the petrous portion of the temporal bone. The labyrinthine wall of the tympanic cavity separates the bony labyrinth from the middle ear. Within the bony labyrinth lies the membranous labyrinth that consists of small sacs and tubules which contain receptors for hearing, movement of the head, and position of the head.

The vestibule is the central part of the bony labyrinth that encloses the membranous sacs - saccule and utricle.

The semicircular canals are three bony canals situated behind the vestibule and arranged in three mutually perpendicular planes. The semicircular canals of the bony labyrinth contain perilymphatic fluid and enclose the membranous semicircular ducts.

The cochlea is a bony canal that forms a spiral making 2.5 turns, and lies in front and medially of the vestibule. The cochlea of the bony labyrinth encloses the membranous cochlear duct.

Apart from these three parts, the bony labyrinth also houses the vestibulocochlear organ with the spiral organ of the Corti and the vestibular nerve.

The innervation and vasculature of the bony labyrinth and its structures are discussed in the articles on the internal ear, as the vascularization and innervation of many structures are the same and overlapping.