Anatomy of the inner ear

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Anatomy of the inner ear

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USMLE® Step 1 questions

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Figure 1: Vestibulocochlear organ.
Figure 2: Anatomy of the cochlea.


USMLE® Step 1 style questions USMLE

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A 36-year-old rockstar is being evaluated by their primary care doctor for progressive hearing loss over the last two years. They state that they have not been wearing ear protection while rocking out during loud concerts. A physical examination and a series of tests would most likely reveal results consistent with damage to hair cells located in which part 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.


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