Fenestra cochleae

Fenestra cochleae or round window is one of the two openings from the middle ear into the inner ear. It is sealed by the secondary tympanic membrane, also known as the round window membrane. This membrane vibrates with opposite phase to vibrations entering the inner ear through the other opening, the fenestra vestibuli, also known as the oval window. This results in a pressure relief mechanism for the fluid-filled inner ear, allowing the fluid in the cochlea to move, which in turn ensures that the hair cells of the basilar membrane will be stimulated and auditory signals will be sent to the brain.

Structure[edit | edit source]

The fenestra cochleae is located in the bony labyrinth of the ear, which is a system of passages making up two main functional parts: the cochlea for transmitting sound, and the vestibular system for maintaining balance. The round window sits directly below the oval window and posterior to the cochlear duct.

Function[edit | edit source]

The primary function of the fenestra cochleae is to allow movements of the fluid within the cochlea, leading to stimulation of the sensory hair cells. When the stapes vibrates against the oval window in response to sound, it causes waves in the fluid inside the cochlea. The round window membrane moves out during the inward movement of the stapes and vice versa, allowing the fluid to move.

Clinical significance[edit | edit source]

In some cases, the fenestra cochleae may be obscured or covered by bone, a condition known as round window atresia. This can lead to conductive hearing loss. Surgical intervention may be necessary to correct this condition.