Post on 15-Jan-2016
description
Labyrinths containLabyrinths contain
Three partsThree parts
Semicircular canals Semicircular canals
Vestibular Vestibular
systemsystem
VestibuleVestibule
CochleaCochlea Auditory Auditory systemsystem
Vestibular systemVestibular system
Function: Balance and equilibriumFunction: Balance and equilibrium
Sensory cells: Hair cellsSensory cells: Hair cells
Auditory system: CochleaAuditory system: Cochlea
Name derived from snail-Name derived from snail-like shapelike shape
Tube of decreasing Tube of decreasing diameter coiled around diameter coiled around itselfitself
Coiled around a central Coiled around a central bony canal called modiolus bony canal called modiolus
Broad base, narrow apexBroad base, narrow apex
Length: About 35 mm Length: About 35 mm
In human beings: 2 and 5/8 In human beings: 2 and 5/8 coilscoils
Isolated cochlear turns from the inner ear of fetal sheep: Photo courtesy of Gerhardt, Isolated cochlear turns from the inner ear of fetal sheep: Photo courtesy of Gerhardt, K. K.
Cochlear macrostructureCochlear macrostructure
Partially divided Partially divided throughout its throughout its length by a thin length by a thin spiral shelf of bone spiral shelf of bone called called osseous osseous spiral laminaspiral lamina
At the outer At the outer (lateral) wall of the (lateral) wall of the cochlea: cochlea: Spiral Spiral ligamentligament
Between the osseous spiral Between the osseous spiral lamina and the spiral lamina and the spiral ligament: ligament: Basilar Basilar membranemembrane
Runs all the way along the Runs all the way along the length of the cochlea, length of the cochlea, except for a small opening except for a small opening at the apex called the at the apex called the helicotremahelicotrema
Reissner’s membraneReissner’s membrane projects diagonally from projects diagonally from spiral lamina to outer bony spiral lamina to outer bony wall of cochleawall of cochlea
Joins the basilar membrane Joins the basilar membrane at the helicotremaat the helicotrema
Between the osseous spiral Between the osseous spiral lamina and the spiral lamina and the spiral ligament: ligament: Basilar Basilar membranemembrane
Runs all the way along the Runs all the way along the length of the cochlea, length of the cochlea, except for a small opening except for a small opening at the apex called the at the apex called the helicotremahelicotrema
Reissner’s membraneReissner’s membrane projects diagonally from projects diagonally from spiral lamina to outer bony spiral lamina to outer bony wall of cochleawall of cochlea
Joins the basilar membrane Joins the basilar membrane at the helicotremaat the helicotrema
http://www.iurc.montp.inserm.fr/cric/audition/english/ear/fear.htm
http://epl.meei.harvard.edu/~hwang/3Dviewer/3Dviewer.html
Cross-section of the cochleaCross-section of the cochlea
Basilar membrane and Basilar membrane and Reissner’s membrane Reissner’s membrane divide the cochlear divide the cochlear canal into three ducts:canal into three ducts:
Scala vestibuliScala vestibuli Scala tympaniScala tympani Scala mediaScala media
Scala Vestibuli Scala Vestibuli
Above Reissner’s Above Reissner’s membranemembrane
Extends from oval Extends from oval window in the window in the vestibule to the vestibule to the helicotremahelicotrema
Contains perilymphContains perilymph
Scala TympaniScala Tympani
Below the basilar Below the basilar membranemembrane
Extends from round Extends from round window to the window to the helicotremahelicotrema
Contains perilymphContains perilymph
Scala media/cochlear sacScala media/cochlear sac
Bound below by Bound below by basilar membranebasilar membrane
Bound above by Bound above by Reissner’s membraneReissner’s membrane
Bound on the outer Bound on the outer side by side by Stria Stria vascularisvascularis
Contains endolymphContains endolymph
Dimensions of the cochlear partitionsDimensions of the cochlear partitions
Cochlea: Narrower toward the apexCochlea: Narrower toward the apex
Basilar membrane: Narrower at the base and wider Basilar membrane: Narrower at the base and wider toward the apical endtoward the apical end
Apical end: Flaccid and under no tensionApical end: Flaccid and under no tension
Base end: Stiff and under a small amount of tensionBase end: Stiff and under a small amount of tension
Cochlear microstructure Cochlear microstructure
Organ of CortiOrgan of Corti
Lies on the basilar Lies on the basilar membrane in the membrane in the scala mediascala media
Contains many Contains many different types of different types of specialized cellsspecialized cells
Organ of CortiOrgan of Corti
Pillar cells or rods of CortiPillar cells or rods of Corti
Provide structure and Provide structure and supportsupport
Inner and outer Inner and outer pillar cellspillar cells
Form a tunnel called Form a tunnel called tunnel of Cortitunnel of Corti
Contains fluid called Contains fluid called cortilymphcortilymph
Hair cellsHair cells
On the outer side of On the outer side of the outer pillar/rod the outer pillar/rod cells: cells: Outer hair Outer hair cells (OHC)cells (OHC)
(Away from modiolus)(Away from modiolus)
On the inner side of On the inner side of the inner pillar/rod the inner pillar/rod cells: cells: Inner hair cells Inner hair cells (IHC)(IHC)
(Toward the modiolus)(Toward the modiolus)
Supporting cellsSupporting cells
OHC supported by OHC supported by cells of cells of Deiter and Deiter and HensenHensen
IHC supported by IHC supported by border cells of border cells of the inner sulcusthe inner sulcus
Reticular laminaReticular lamina
Formed partly by the Formed partly by the phalangeal phalangeal processes of the Deiter’s cells.processes of the Deiter’s cells.
OHCOHC Around 12000 in numberAround 12000 in number
Test-tube shapedTest-tube shaped
Three-five rowsThree-five rows
IHCIHC
Around 3400 in Around 3400 in numbernumber
Flask shapedFlask shaped
Single rowSingle row
Stereocilia Stereocilia
Hairlike projectionsHairlike projections
Project from the top of Project from the top of IHC and OHCIHC and OHC
Graded in lengthGraded in length
Have cross-bridges Have cross-bridges called tip-linkscalled tip-links
Stereocilia of OHC and IHCStereocilia of OHC and IHC
OHC: OHC: 6-7 rows per OHC6-7 rows per OHC Each row has a W Each row has a W
shaped arrangementshaped arrangement
IHC: IHC: 2-4 rows per IHC2-4 rows per IHC Each row in a shallow Each row in a shallow
U-shaped U-shaped arrangementarrangement
Tectorial membraneTectorial membrane
Gelatinous transparent Gelatinous transparent membrane projecting from membrane projecting from spiral laminaspiral lamina
Attaches loosely on outer Attaches loosely on outer edge to the Deiter’s and edge to the Deiter’s and Hensen’s cells.Hensen’s cells.
Longest stereocilia of OHC Longest stereocilia of OHC embedded in inferior embedded in inferior surface of tectorial surface of tectorial membranemembrane
Stereocilia of IHC not Stereocilia of IHC not embedded in tectorial embedded in tectorial membranemembrane