- The middle ear contains several key anatomical structures involved in the conduction of sound.
- Among these, the ossicles — which comprise the malleus, incus, and stapes — play a crucial role.
- These tiny bones form a mechanical chain that transmits vibrations from the tympanic membrane (eardrum) to the oval window of the inner ear.

Here is a brief overview of the options:
- Tympanic membrane: Although it vibrates in response to sound waves, the tympanic membrane's primary role is to capture and convert sound waves from the external auditory canal into mechanical vibrations. It does not conduct sound deeper into the ear by itself.

- Ossicles: These small bones amplify and transmit vibrations from the tympanic membrane to the inner ear. The stapes interfaces with the oval window, effectively transmitting sound energy into the fluid-filled cochlea.

- Cochlear nerve: This nerve transmits electrical signals from the cochlea to the brain but does not conduct sound waves physically.

- External auditory canal: This canal directs sound waves toward the tympanic membrane but is not involved in conduction within the middle ear.

Therefore, the correct answer is Ossicles, since they are the essential anatomical structures responsible for conducting and amplifying sound from the middle ear to the inner ear.

Reference: Gray's Anatomy, 42nd Edition, Volume 1, Chapter 30 - Ear