Internal ear

The internal ear consists of two labyrinthine compartments, one contained within the other

The bony labyrinth is a complex system of interconnected cavities and canals in the petrous part of the temporal bone. The membranous labyrinth lies within the bony labyrinth and consists of a complex system of small sacs and tubules that also form a continuous space enclosed within a wall of epithelium and connective tissue. There are three fluid-filled spaces in the internal ear:

• Endolymphatic spaces, contained within the membranous labyrinth. The endolymph of the membranous labyrinth is similar in composition to miracellular fluid (it has a high K+ concentration and low Na+ concentration).

• Perilymphatic space, lying between the wall of the bony labyrinth and the wall of the membranous labyrinth. The perilymph is similar in composition to extractlular fluid (it has a low K+ concentration and a high Na+ concentration).

• Cortilymphatic space, lying within the organ of Corti. It is a true intercellular space. The cells surrounding the space loosely resemble an absorptive epithelium. The cortilymphatic space is filled with cortilymph, which has a composition similar to that of extracellular fluid.

The bony labyrinth consists of three connected spaces within the temporal bone

The three spaces of the bony labyrinth, as illustrated in

Figure 24.6, are

• Semicircular canals

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