The pharynx and the middle ear are connected to each other by the .........

The part of the ear which distinguishes different pitches of sound is

Structures filled with perilymph - $P$
Structures filled with endolymph - $Q$
$I -$ Scala vestibuli,$II -$ Scala tympani,$III -$ Scala media
Select the correct option for $P$ and $Q$.
$P \quad\quad Q$

Eustachian tube connects .......$A$......... cavity with ......$B$......

The lower membrane of the $scala$ $vestibuli$ is the:

The components of the vestibular apparatus are: