The ear is divided into outer, middle, and inner regions with associated structures that are specialized for sound perception. In addition, receptors for the senses of balance and spatial orientation comprise the vestibular apparatus, which is also part of the inner ear.

The learning objective for this unit is:

• Identify the membranous labyrinth (utricle, saccule, semicircular ducts, and cochlear duct) and their corresponding receptor and supporting cells, and explain how they relate to vestibular and hearing function.

Let’s start with the inner ear.