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anatomyofinnerear-150709161800-lva1-app6891.pdf
1. Anatomy of Inner ear
Anatomy of Inner ear
Dr Ramesh Parajuli,MS
Chitwan Medical College Teaching Hospital,Bharatpur-10,Chitwan,Nepal
2.
3.
4.
5. The inner(internal) ear is
called as labyrinth, from the
complexity of its shape.
It consists of two parts:
1. The bony labyrinth: A series
of cavities within the petrous
part of the temporal bone.
2. The membranous labyrinth:
A series of communicating
membranous sacs and
ducts, contained within the
bony cavities.
6. Inner ear fluids
Membranous labyrinth= endolymph
Space between membranous and bony
labyrinth= perilymph
Perilymph:
Exact origin not known
Serum infiltrate, CSF
Rich in Na (similar to ECF and plasma)
Endolymph:
Origin: Stria vascularis
Rich in K ion (similar to Intracellular fluid)
Absorption: Endolymphatic sac
7. Bony(osseous) labyrinth
The bony labyrinth consists of 3 parts:
1. Cochlea: anteriorly
2. Vestibule: middle
3. Semicircular canals: posteriorly
Derived from Ottic capsule
8.
9. The Vestibule
It is central part of the bony labyrinth, and is situated
medial to the tympanic cavity, behind the cochlea,
and in front of the semicircular canals.
In its lateral or tympanic wall is the fenestra
vestibuli, closed by the base of the stapes and
annular ligament.
10. Two recesses:
1. Spherical recess: lodges Saccule
2. Elliptical recess: lodges Utricle
Below elliptical recess is the opening of
aqueduct of vestibule through which passes
the endolymphatic duct
Vestibule has 5 openings of 3 Semicircular
canals(SCC)
11.
12. Semicircular canals(SCC)
3 in numbers:
Lateral(horizontal)
Posterior
Superior
Lies at right angles to each other
Each canal has an ampullated end and non-
ampullated end
Non-ampullated ends of PSCC and SSCC unite to
form a common channel Crus commune
3 SCC have 5 openings into Vestibule
13. Cochlea
A spiral shaped fluid
filled structure
Coiled tube making
2.5 to 2.75 turns
around a central
pyramid of bone=
Modiolus
14.
15. Thin plate of bone winding spirally around modiolus like
a thread of screw= bony spiral lamina
16. Organ of corti through which electircal impulse(sound)
are sent along the auditory(cochlear) nerve to the brain
17. Basal turn of cochleabony bulge in the
medial wall of middle ear= Promontory
Bony Cochlea contains 3 compartments:
1. Scala vestibuli: closed by stapes footplate, contains
perilymph
2. Scala tympani: closed by secondary membrane,
contains perilymph.
3. Scala media (membranous cochlea):endolymph
18. Scala tympani is connected to subarachnoid space
through aqueduct of cochlea
19. Scala vestibule and scala tympani connects to each other
at the apex of cochlea Helicotrema
20. Membranous labyrinth
Series of communicating sacs and ducts
Filled with endolymph
Within walls epithelium,specialized to form sensory
receptors of cochlear and vestibular labyrinth
It consists of
1. Cochlear duct
2. Utricle and saccule
3. Semicircular ducts
4. Endolymphatic duct and sac
21.
22. Cochlear duct(membranous cochlea)
Blind coiled tube
Triangular on cross section
3 walls:-
1. Basilar membrane: supports organ of corti
2. Reissner’s membrane(Roof of cochlear duct)
separates it from scala vestibuli
3. Stria vascularis: contains vascular epithelium.
secrets endolymph
Cochlear duct is connected to the saccule by ductus
reuniens.
23. Organ of Corti:
contains auditory
sensory cells and
complex arrangement
of supporting cells
Hair cells – inner and
outer
Stereocilia or “hairs”
electircal
impulse(sound) are
sent along the
auditory(cochlear)
nerve to the brain
28. Utricle and saccule
Utricle and saccule
Macula(Sensory epithelium): concerned with
balance i.e. linear acceleration and position of head
in response to gravity
29. Semicircular
Semicircular ducts
3 in numbers
Ampulated and non-ampulated end
Ampulated end of each duct contains
neuroepithelium: crista ampularis concerned with
balance i.e. Angular acceleration
30. Endolymphatic duct and sac
Endolymphatic duct and sac
Formed by the union of 2 ducts, one each from the saccule
and utricule
Endolymphatic duct passes through the vestibular
aqueductterminal part dilated to form endolymphatic sac
Endolymphatic sac lies between the two layers of Dura
31. Peripheral receptors of auditory and
vestibular system
Peripheral receptors of auditory pathway:
Organ of Corti: cochlear hair cells
Peripheral receptors of vestibular pathway:
1.Cristae: located in ampullated ends of 3
Semicircular ducts
-responds to angular acceleration
2.Maculae:
Located in otolith organs(i.e. utricle and saccule)
-sense position of head in response to gravity and
linear acceleration
33. Vestibular Hair Cells
Vestibular Hair Cells
Type I vestibular cells: compare with inner cochlear hair cells (in Organ of
corti)-flask(cup)shaped
Type II vestibular cells: compare with outer cochlear hair cells-cylindrical