The perilymphatic space, part of the inner ear’s intricate structure, plays a crucial role in the functioning of the auditory and vestibular systems.
Structure
The perilymphatic space refers to the set of interconnected cavities within the bony labyrinth of the inner ear filled with perilymph fluid. This space encompasses the scala vestibuli and scala tympani within the cochlea, as well as the vestibular aqueduct and spaces surrounding the membranous labyrinth of the vestibular system. Unlike the endolymph that fills the membranous labyrinth, perilymph is similar in ionic composition to cerebrospinal fluid, being rich in sodium ions.
The perilymphatic space serves as a protective and supportive environment for the membranous labyrinth. It cushions the delicate structures of the inner ear and facilitates the transmission of sound waves and the operation of the vestibular apparatus.
- In the Cochlea: Within the cochlea, the perilymphatic space is divided into two main sections: the scala vestibuli, which begins near the oval window, and the scala tympani, ending at the round window. These two chambers are separated from the cochlear duct (scala media) by the Reissner’s membrane (above) and the basilar membrane (below), respectively.
- In the Vestibular System: The perilymphatic space extends around the semicircular canals, utricle, and saccule of the vestibular labyrinth. This arrangement allows for the proper functioning of the balance organs as they respond to the body’s movements.
Function
The primary function of the perilymphatic space and the perilymph fluid is to transmit mechanical forces within the inner ear. In the cochlea, perilymph plays a critical role in the transmission of sound vibrations from the oval window through the scala vestibuli and scala tympani towards the round window. This movement of perilymph causes the basilar membrane to vibrate, stimulating the sensory hair cells in the organ of Corti to convert these mechanical vibrations into electrical signals for the brain to interpret as sound.
In the vestibular system, the perilymphatic space helps to transmit forces resulting from head movements and positional changes, facilitating the activation of sensory receptors in the semicircular canals, utricle, and saccule. These receptors then send signals to the brain regarding the body’s orientation and motion, contributing to balance and spatial awareness.
