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Inner Ear
Midterm #2
36
Audiology
Undergraduate 3
10/27/2009

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Term
How many labyrythns are there in the Otic Capsule and name them
Definition
Bony and Membranous
Term
Describe the Bony Labyrinth
Definition
It is a a series of cavities within the petrous portion of the temporal bone
Term
Describe the Membranour Labyrinth
Definition
It is a series of soft tissue canals, sacs, and ducts within the bony labyrinth; follows the bony labyrinth in shape, but is smaller
Term
Name three components of the Bony Labyryth
Definition
Auditory System - Cochlea, Vestibular System - 3 Semicircular Canals, Vestibule
Term
What is the space between the osseous and membranous labyrinths called? What is it filled with?
Definition
Perlymphatic Space/ A fluid called Perilymph
Term
Describe perilymph and what is it similar to?
Definition
High in sodium (Na+) and low in potassium (K+); a chemical composition similar to that found in cerebral spinal fluid, but its source is not completely known
Term
What is the membrabous labyrinth filled with?
Definition
Endolymph
Term
Describe endomymph. Where is it produced?
Definition
high in potassium (K+), and low in sodium (Na+). This fluid is produced by the stria vascularis, a structure found inside the cochlea.
Term
Is there any communication between the membranous labyrinth and the bony one?
Definition
No (think of inner tube inside tire
Term
Describe the Cochlea
Definition
The auditory portion of the inner ear is
called the COCHLEA. It is cone
shaped and measures 5mm from its base to
apex and 9mm across its breadth of the base. It is a coiled structure with 23/4 turns or coils that coil around a bony central canal called the MODIOLUS
Term
Describe the bony cochlea
Definition
The bony canal is about 35mm in length
and narrows from base to apex. There
are two major openings in the bony
canal: the oval window and the round
window
Term
Name the three scalae of the cochlea?
Definition
Scala Vestibuli, Scala Media, Scala Tympani
Term
Describe how the membranous labyrinth changes from base to apex as it follow the osseous labyrinth?
Definition
Instead of narrowing at the apex, it widens. It is also stiffer at the base, and flaccid at the but instead of
narrowing at the apex, it widens. It is
also stiffer at the base, and flaccid at the apex.
Term
What's another name for the scala vestibuli?
Definition
Cochlear duct
Term
What is the bony scala filled with? Scala media?
Definition
The bony scalae are filled with perilymph and the scala media is filled with endolymph.
Term
About how many IHC are there? What shape are they?
Definition
3500/ flask-shaped
Term
About how many OHC are there? What shape are they?
Definition
12500/ tubular
Term
Do OHC/IHC run longitudinally? Where do they run along?
Definition
T/ basilar membrane
Term
Stereocilia are not of graduated height. T or F
Definition
F
Term
Stereocilia contain which chemical? Why?
Definition
Actin for contracting and becoming stiff
Term
IHC have about how many stereocilia? What shape are they?
Definition
60 IHC shallow cresent-shaped
Term
OHC have how many stereocilia? What shape are they?
Definition
20/100/OHC W-shaped
Term
Where do stereocilia sit
Definition
Within the reticular lamina
Term
What is the tectorial membrane? What is it composed of? Where dows it project from?
Definition
A gelatinous mass overlying the OHC that is essentially transparent (90%) water. Projects from the spirous limbus.
Term
In the Tunnel of Corti, what cells surround it? Where do they sit? What are the OHC/IHC bathed in? How about the stereocilia?
Definition
Tunnel of Corti is surrounded by pillar cells which sit on the Basilar Membrane.
OHCs and IHCs bathed in perilymph
Stereocilia bath in endolymph
Term
What three elements is the Vestibular System composed of?
Definition
SEMICIRCULAR CANALS, the
space between the canals and the
cochlea known as the VESTIBULE,
and the organs within it, the UTRICLE
and the SACCULE.
Term
Describe the Vestibule
Definition
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
What do the IHC/ OHC sit on?
Definition
Sensory Epithilium called the Crista
Term
Where are the stereo cilia embedded?
Definition
A gelatinous mass called the Cupula
Term
What is the Utricle?
Definition
A soft tissue structure
housed in the vestibule
Term
Where do the semi-circular canals open? Where is this located? What liquid surrounds it and what's inside?
Definition
They open into the Utricle, which is located in the posterior-superior
aspect of the vestibule. It's is surrounded by perilymph and is filled with endolymph
Term
What is the Macula? What covers it?
Definition
This is a flat plate where the sensory cells of the utricle sit. The cells
are covered with a gelatinous substance
containing calcium carbonate crystals or
Otoliths. There are some supporting cells as well.
Term
Describe the Saccule in relation to the Utricle. Where does it lie?
Definition
Term
What is the Ductis Reuniens? What does it do?
Definition
A short tube that is part of the membranous labyrinth and connects the vestibular organs to the cochlea
Term
Where does the Endolymphatic Duct lead in the brain?
Definition
It is extension of the membranous labyrinth into the dural area of the brain which leads to the endolymphatic sac
Term
Where does the perilymph of the bony labyrinth lead? Through what structure>
Definition
Connects to the cerebral spinal fluid through a narrow canal called the cochlear aqueduct
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