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21 Cards in this Set

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Describe the Osseous Cochlea
Anterior area of the bony labyrinth...
Hollow tube-2 5/8 turns around a core
What is the core of the Osseous Cochlea?
Modiolus, latin for hub
Describe the osseous spiral lamina
Crest of bone (like a flange of screw) that projects out from the modolius into the opening of the osseous cochlear tube and partially divides it into 2 divisions.
What are the 2 divisions of the osseous cochlea and where are they located (top/bottom)?
Scala (l. staircase) vestibule (top)
Scala tympani (bottom)
What happens at the apex of the cochlear tube? What is this called?
The OSL disappears to allow communication between the SV and ST. This opening is called the HELIOCTREMA (l. coil/hole)
Describe the shape and dimensions of the cochlea.
Width of base=9 mm
Base to Apex=5mm
Cochlear tube length (when rolled out)=35 mm
What is the Foramen Centrale?
Large opening in the base of the cochlea, where nerves from the apex pass through
What is the Tractus Spiralas Foramina?
Spiral tract (speckled dots) on the periphery of the base, where nerves from the base pass through
Describe the osseous spiral lamina and its 3 major components.
2 thin shelves of bone projecting into the lumen of the cochlear tube opening. 3 major components: 1) perforate habenula; 2) vestibular lip and 3) tympanic lip
What is the perforate habenula?
Part of OSL; where the accoustic nerve from sensory cells run
What does the Internal Auditory Meatus carry?
Passageway in bone that will carry the 8th Cranial Nerve from the Cochlea eventually to the Cortex
Describe the presence of the OSL in the cochlear tube.
OSL has the greatest presence/width at the base; projects less into tube toward the apex; then dissapears at the apex
What is the medialmost portion of the osseous labyrinth?
Cochlea; bony canal about 35 mm in length which is coiled upon itself around a central core of bone called the modiolous
Where is the base of the modiolus located?
it is broad and is located at the bottom of the internal auditory meatus, which in life carries the auditory nearve, facial nerve, nervus intermedius and the internal branch of the basilar artery.
What is the cochlea a continuation of?
Vestibule
What is the hamulus?
Near the apex of the cochlea the spiral lamina terminates as a hooklike process called the hamulus, which assists in forming the boundary of a small opening, the helicotrema.
How many openings does the cochlea have?
three
Explain how the round window and its role in the cochlea
One of the openings of the cochlea located at the basal extreme of the scala tympani. It opens into the tympanic cavity, however it is closed off by a thin secondary tympanic membrane. It permits pressures to equalize between the scala vestibuli and the scala tympai.
Name the very small aperture (crack,hole) near the round window in the scala tympani
cochlear aqueduct
What lines the bony labyrinth?
thin, fibroserous membrane that is closely adherent to the bone. Its free surface is covered with epithelium that secretes perilymph
What type of fluid fills the scala vestibule, scala tympani?
perilymph