Question

Fenestra ovalis is the opening of
A. Cranium
B. Tympanum
C. Tympanic cavity
D. Brain

Answer 1

Hint: It is also known as the fenestra vestibuli or oval window.

Complete answer:
‘Fenestra ovalis' is a membranous connective tissue that is present in the Tympanic cavity at the junction of the middle ear and inner ear. It is a reinform or kidney-shaped opening that opens into the vestibule of the cochlea present in the inner ear. On the outer side, it is connected to the base of the stapes bone. The vibrations carried by the three ossicles are amplified and then taken by the oval window to transfer it to the cochlea.

Additional Information:
> The junction of the middle ear and inner ear also possess another opening known as the ‘Round window.
> It is also known as the Fenestra rotundum or Fenestra cochleae and remains covered by the round window membrane.
> It is present a little below and behind the oval window separated by a promontory.
> When the fluid in the oval window is displaced by the pressure applied by the stapes, the fluid in the round window also moves in the opposite phase i.e. when the membrane of the oval window vibrates outwards, the round window membrane vibrates inwards.
> This coordinated movement helps the cochlear fluid to move, the vibrations are carried to the hair cells and hair cells move against the tectorial membrane to produce a hearing sensation.

So, the correct answer is the Tympanic cavity.

Note:
- Cochlea consists of the organ of Corti, the sensory organ responsible for hearing.
- Cochlear has two parts, the bony labyrinth and the membranous labyrinth filled with perilymph and endolymph respectively.
- The bony labyrinth is further divided into upper scala vestibuli and lower scala tympani.
- The Scala vestibuli opens into the oval window whereas the scala tympani terminates into the round window.