About Hearing:

The human ear comprises 3 sections – Outer, Middle and Inner Ear.
The inner ear contains the cochlea and auditory nerve
The ear can be divided into 3 major sections:

Outer Ear

Pinna (external ear) – concentrates sound waves and conducts them into the External Auditory Meatus. External Auditory Meatus (ear canal) – acts as a tubular resonator so sound vibrations have a higher pressure at the eardrum than external to the Pinna.

Middle Ear

Tympanic Membrane (eardrum) – composed of circular and radial fibres. It is kept tense by the tensor tympani muscles. The eardrum acts as a receptor of sound vibrations and protects the delicate contents of the inner ear.
Ossicles (Malleus, Incus, Stapes) – The three smallest bones in the human body. They conduct the vibrations of the eardrum to the inner ear.

Inner Ear

A cross-section of the cochlea identifies:

• Scala vestibuli – filled with perilymph
• Scala media (cochlear duct) – filled with endolymph. Has vestibular (Reissner’s) membrane above and basilar membrane below; and
• Scala tympani – filled with perilymph

The Organ of Corti sits on the basilar membrane and consists of highly specialised receptor hair cells, which are attached to the tectorial membrane. Each of these hair cells is supplied by at least one nerve fibre connected to a spiral ganglion.