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Labyrinths contain

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Title: Other examples of complex waves Author: Mini Shrivastav Last modified by: Mini Shrivastav Created Date: 7/8/2004 12:57:35 PM Document presentation format – PowerPoint PPT presentation

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Title: Labyrinths contain


1
Labyrinths contain
  • Three parts
  • Semicircular canals
  • Vestibular
    system
  • Vestibule
  • Cochlea Auditory system

2
Vestibular system
  • Function Balance and equilibrium
  • Sensory cells Hair cells

3
Auditory system Cochlea
  • Name derived from snail-like shape
  • Tube of decreasing diameter coiled around itself
  • Coiled around a central bony canal called
    modiolus
  • Broad base, narrow apex
  • Length About 35 mm
  • In human beings 2 and 5/8 coils

4
Isolated cochlear turns from the inner ear of
fetal sheep Photo courtesy of Gerhardt, K.
5
Cochlear macrostructure
  • Partially divided throughout its length by a thin
    spiral shelf of bone called osseous spiral lamina
  • At the outer (lateral) wall of the cochlea
    Spiral ligament

6
  • Between the osseous spiral lamina and the spiral
    ligament Basilar membrane
  • Runs all the way along the length of the cochlea,
    except for a small opening at the apex called the
    helicotrema
  • Reissners membrane projects diagonally from
    spiral lamina to outer bony wall of cochlea
  • Joins the basilar membrane at the helicotrema

7
  • Between the osseous spiral lamina and the spiral
    ligament Basilar membrane
  • Runs all the way along the length of the cochlea,
    except for a small opening at the apex called the
    helicotrema
  • Reissners membrane projects diagonally from
    spiral lamina to outer bony wall of cochlea
  • Joins the basilar membrane at the helicotrema

http//www.iurc.montp.inserm.fr/cric/audition/engl
ish/ear/fear.htm
http//epl.meei.harvard.edu/hwang/3Dviewer/3Dview
er.html
8
Cross-section of the cochlea
  • Basilar membrane and Reissners membrane divide
    the cochlear canal into three ducts
  • Scala vestibuli
  • Scala tympani
  • Scala media

9
Scala Vestibuli
  • Above Reissners membrane
  • Extends from oval window in the vestibule to the
    helicotrema
  • Contains perilymph

10
Scala Tympani
  • Below the basilar membrane
  • Extends from round window to the helicotrema
  • Contains perilymph

11
Scala media/cochlear sac
  • Bound below by basilar membrane
  • Bound above by Reissners membrane
  • Bound on the outer side by Stria vascularis
  • Contains endolymph

12
Dimensions of the cochlear partitions
  • Cochlea Narrower toward the apex
  • Basilar membrane Narrower at the base and wider
    toward the apical end
  • Apical end Flaccid and under no tension
  • Base end Stiff and under a small amount of
    tension

13
Cochlear microstructure
  • Organ of Corti
  • Lies on the basilar membrane in the scala media
  • Contains many different types of specialized cells

14
Organ of Corti
15
Pillar cells or rods of Corti
  • Provide structure and support
  • Inner and outer pillar cells
  • Form a tunnel called tunnel of Corti
  • Contains fluid called cortilymph

16
Hair cells
  • On the outer side of the outer pillar/rod cells
    Outer hair cells (OHC)
  • (Away from modiolus)
  • On the inner side of the inner pillar/rod cells
    Inner hair cells (IHC)
  • (Toward the modiolus)

17
Supporting cells
  • OHC supported by cells of Deiter and Hensen
  • IHC supported by border cells of the inner sulcus

18
Reticular lamina
  • Formed partly by the phalangeal processes of the
    Deiters cells.

19
OHC
  • Around 12000 in number
  • Test-tube shaped
  • Three-five rows

20
IHC
  • Around 3400 in number
  • Flask shaped
  • Single row

21
Stereocilia
  • Hairlike projections
  • Project from the top of IHC and OHC
  • Graded in length
  • Have cross-bridges called tip-links

22
Stereocilia of OHC and IHC
  • OHC
  • 6-7 rows per OHC
  • Each row has a W shaped arrangement
  • IHC
  • 2-4 rows per IHC
  • Each row in a shallow U-shaped arrangement

23
Tectorial membrane
  • Gelatinous transparent membrane projecting from
    spiral lamina
  • Attaches loosely on outer edge to the Deiters
    and Hensens cells.
  • Longest stereocilia of OHC embedded in inferior
    surface of tectorial membrane
  • Stereocilia of IHC not embedded in tectorial
    membrane

24
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