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Anatomy of the Inner Ear
Study for Exam 2
33
Audiology
Undergraduate 3
10/26/2009

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Term
What serves as the separation between the middle and inner ear?
Definition
The oval window
Term
Components of the Bony Labyrinth (Inner Ear)
Definition
Auditory System: Cochlea
Vestibular System: Three Semi-Circular Canals
Vestibule
Term
[image]
Definition
Term
Otic Capsule
Definition
The skeletal element enclosing the inner ear mechanism.
Term
The two labyrinths of the inner ear...
Definition
Osseous: a series of cavities within the petrous portion of the temporal bone.

There is no communication between the two labyrinths; much like an inner tube inside a tire.


Membranous: a series of soft tissue, canals, sacs, and ducts within the bony labyrinth; follows the bon labyrinth in shape, but is smaller.
Term
The space between the osseous and membranous labyrinths is called the
Definition
Perilymphatic Space
Term
The perilymphatic space is filled with a fluid called...
Definition
Perilymph which is high in sodium (Na+) and low in sodium (K+); a chemical composition similar to that found outside all cells of the body called interstitial fluid. Probably a blood product from capillaries.
Term
The membranous labyrinth is filled with a fluid called...
Definition
Endolymph which is is high in potassium (K+), and low in sodium (Na+)
Term
Endolymph is a product of what?
Definition
by the stria vascularis, a structure found inside the cochlea
Term
The auditory portion of the inner ear is called...
Definition
The Cochlea
Term
Describe the cochlea
Definition
5mm from base to apex 9m across.
35mm in length and narrows from base to apex
A coiled structure with 2 and 3/4 turns that coil around a bon central canal called the modiolus
Term
The central pillar of the cochlea is called the
Definition
modiolus
Term
What are he two major openings in the cochlea?
Definition
The oval and round windows
Term
What are the three chambers of scala?
Definition
Scala Vestibuli
Scala Tympani
Scala Media
Term
[image]
Definition
Term
Instead of narrowing at the apex the membranous cochlea...
Definition
widens.
Term
The membranous cochlea is ______ at the base and _____ at the apex.
Definition
stiffer
flacid
Term
The Scala Vestibule and Scala Tympani are filled with _______ while the Scala Media is filled with _______
Definition
perilymph
endolymph
Term
10 Structures of the Cochlea
Definition
1) Basilar Membrane
2) Organ of Corti
3) Outer Hair Cells
4) Inner Hair Cells
5) Reissner's Membrane
6) Tectorial Membrane
7) Stria Vascularis
8) Spiral Ligament
9) Spiral Ganglion
10) Osseous Spiral Lamina
Term
[image]
Definition
Term
Describe the hair cells in the organ of corti
Definition
One row of inner hair cells (3500) - flask shaped
Three rows of Outer Hair Cells (12,500) - tubular shape

All hairs run longitudinally along the basilar membrane
Term
Describe stereocilia within the organ of corti
Definition
fine hairlike structures that sit on the tops of each row of inner and outer hair cells with graduated heights

The are stiff structures due to actin

60 stereocilia/IHC; shallow crescent
20/100 stereocilia/OHC; W shaped

Sit within the reticular lamina
Term
Describe the tectorial membrane.
Definition
-A gelatinous mass overlying the OHC
-90% water
-Essentially transparent
-Projects from the spiral limbus
Term
The tunnel of corti
Definition
- a spiral passage in the organ of Corti
- surrounded by pillar cells
-Inner and Outer pillar cells sit on the basilar membrane
- Spaces of Nuel between the OHC's
- Supporting cells (Hensens, Claudius)
- OHC's and IHC's bathed in perilymph
- Stereocilia bathed in endolymph
Term
The vestibular system is composed of
Definition
three semicircular canals, the space btw the canals and the cochlea known as the vestibule and the organs within it, the utricle and the saccule
Term
Describe the vestibule.
Definition
Measures 5mm front to back and 3mm side to side. The osseous portion has numerous landmarks including recesses for various structures, and holes for nerve fibers to pass to the retrocochlear structures
Term
The Utricle
Definition
a soft tissue structure housed in the vestibule. The semicircular canals open into the utricle. It is located in the posterior-superior aspect of the vestibule. It is surrounded b perilymph and is filled with endolymph.

The sensory cells of the utricle sit on a
flat plate called the macula. The cells
are covered with a gelatinous substance
containing calcium carbonate crystals or
otoliths. There are some supporting cells
as well.
Term
The sensory cells of the utricle sit on a flat plate called the...
Definition
macula
Term
The saccule
Definition
a slightly smaller structure than the utricle that lies in the anterior portion of the vestibule. It's sensory cells are similar to those found in the utricle. It is also surrounded by perilymph and filled with endolymph
Term
Ductus Reuniens
Definition
A short tube that is part of the membranous labyrinth and connects the vestibular organs to the cochlea.
Term
The Vestibular organs are connected to the cochlea by means of the
Definition
Ductus Reuniens
Term
Endolymphatic Duct
Definition
an extension of the membranous labyrinth which leads to the endolymphatic sac.
Term
The perilymph of the bony labyrinth connects to the cerebral spinal fluid through a narrow canal called the...
Definition
cochlear aqueduct
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