Oval window
Fenestra vestibuli
Also known as: fenestra ovalis, vestibular window
A kidney-shaped opening in the medial wall of the middle ear, closed by the stapes footplate and annular ligament, through which sound energy enters the perilymph of the vestibule and scala vestibuli.
Overview
The oval window lies above and behind the promontory, just below the horizontal part of the facial canal, at the bottom of a small depression (the oval window niche). It opens into the vestibule of the bony labyrinth, whose perilymph is continuous with the scala vestibuli of the cochlea.
Inward movement of the stapes footplate pushes perilymph into the scala vestibuli; because fluid is incompressible, the pressure wave displaces the cochlear partition and is relieved by outward bulging of the round window membrane. Effective hearing therefore depends on sound reaching the oval window with greater force than, and out of phase with, the round window — a function of the ossicular chain and intact eardrum ("phase cancellation" otherwise reduces hearing).
- Location
Medial wall of the tympanic cavity, posterosuperior to the promontory, inferior to the facial nerve canal.
Anatomy
- Relations
Facial nerve (tympanic segment) immediately above — at risk in stapes surgery; promontory below; round window posteroinferior.
Function
- Admit stapes vibration to the inner-ear fluids
- Form the entry point of the travelling wave into the scala vestibuli
Clinical significance
Stapes surgery
In otosclerosis the footplate is fixed in the oval window; stapedotomy places a piston prosthesis through the footplate. A dehiscent or overhanging facial nerve is a recognised hazard.
Compiled from standard anatomy and physiology references — see the Special Senses sources. For education only; not medical advice.