Anatomy of the inner ear

How is it you can listen to your favorite song, close your eyes, dance, and not fall on your face? Well, there is a little thing called the inner ear that contains the vestibulocochlear organ which gives you the ability to perceive sounds and maintain your balance.

The inner ear is found in the petrous part of the temporal bone between the middle ear laterally, and the internal acoustic meatus medially. It is a small and important area which houses the irregularly shaped vestibulocochlear organ, which kind of looks like a snail shell attached to a few bony rings.

Now, the inner ear contains the bony labyrinth and the membranous labyrinth. The bony labyrinth is connected to the middle ear by two windows. The oval window is found on the lateral wall of the vestibule and is covered by the base of the stapes, while the round window is found at the base of the cochlea and is covered by the secondary tympanic membrane.

The bony labyrinth, within the otic capsule, is filled with perilymph and is made of a series of cavities which are the vestibule, the semicircular canals, and the cochlea. Suspended within the bony labyrinth, there’s the membranous labyrinth, which is basically a series of sacs and ducts filled with endolymph.

The membranous labyrinth is organized into the utricle and saccule within the vestibule, the three semicircular ducts and their membranous ampullae, and the cochlear duct within the cochlea.

Let’s take a look at the structures responsible for balance, which are the semicircular canals, on the one hand, and the utricle and saccule, on the other hand. There are three semicircular canals, an anterior, posterior, and lateral canal, oriented in the three different planes of space.

Each canal contains a dilated end called the ampulla that contains an area of sensory epithelium called the ampullary crest. This is lined with tiny hair cells that pick up information about rotational movements of the head in the plane of the duct within which it is contained.