Transcript ANATOMY OF INNER EAR

ANATOMY OF INNER EAR
Dr. Supreet Singh Nayyar, AFMC
for more presentations, visit www.nayyarENT.com
www.nayyarENT.com
20-07-2012
• Organ concerned
with hearing and
balance
• Consists of :
a) Bony Labyrinth
b) Membranous
Labyrinth
20-07-2012
www.nayyarENT.com
BONY LABYRINTH
•
Consists of :
a)Vestibule
b)Semicircular
Canals
c) Cochlea
20-07-2012
www.nayyarENT.com
SALIENT FEATURES
www.nayyarENT.com
20-07-2012
MEMBRANOUS
LABYRINTH
• Consists of :
a) Cochlear Duct
b) Utricle & Saccule
c) Semicircular Ducts
d) Endolymphatic
duct & Sac
20-07-2012
www.nayyarENT.com
STRUCTURE OF THE COCHLEAR DUCT
Subdivided into:
• Scala tympani,
Scala vestibuli &
Scala media
• Scala media is
triangular in cross
section
20-07-2012
www.nayyarENT.com
REISSNER’S
MEMBRANE
• Separates Scala
media from Scala
tympani
• Runs obliquely
• Extends from spiral
limbus to lateral
wall
• Consists of 2 layers
of cells separated
by basement
membrane
20-07-2012
www.nayyarENT.com
BASILAR MEMBRANE
• Acellular layer
• Stretches from osseous spiral lamina to the spiral
prominence
• Organ of Corti is situated on the upper surface
• Stretches from spiral limbus to Claudius cells
• Below it lie spindle shaped cells (tympanic cells) & a
branching spiral vessel
www.nayyarENT.com
20-07-2012
SPIRAL LIMBUS
• Composed of interdental cells & main body of
connective tissue cells & blood vessels embedded
in an ECM
• Concave side forms the Inner Sulcus
• Convex surface forms Tectorial membrane
www.nayyarENT.com
20-07-2012
STRIA VASCULARIS
• Forms the lateral
boundary
• Composed of 3 layers of
cells:
Marginal cells
Intermediate cells
Basal cells
• Spiral ligament (fibrocytes
& connective tissue) on
the outer side
• Contains a variety of ion
pumps, enzymes &
transport proteins
20-07-2012
www.nayyarENT.com
www.nayyarENT.com
20-07-2012
CELLULAR ARCHITECHTURE AND
FUNCTION OF ORGAN OF CORTI
• Sensory region consists of
2 types of sensory hair
cells with apical
stereocilia
• Stereocilia project into
the overlying endolymph
• Inner hair cells form a
single row while outer
hair cells form 3-4 rows
• Separated by 2 rows of
pillar cells from the
Tunnel of Corti
20-07-2012
www.nayyarENT.com
SUPPORTING CELLS
• Associated with hair cells
• Inner phalangeal cells & border cells enclose inner
hair cells
• Deiters’ cells enclose outer hair cells & send
phalangeal processes to the adjacent cells
• Hensen’s cells & Claudius’ cells are present on the
outer edge of basilar membrane
www.nayyarENT.com
20-07-2012
OUTER HAIR CELLS
• Cylindrical cells with
flattened upper surface
• Sensory upper end &
synaptic pole at basal
end
• Stereocilia arranged in V
or W shaped rows
• In contact with the
undersurface of tectorial
membrane
20-07-2012
www.nayyarENT.com
STEREOCILIA
• Cylindrical
• Bevelled tip with narrow ankle
region
• Angled towards each other
• Connected by tip links & lateral
links
• Membrane contains proteins
associated with calcium
control & mechanosensitivity
20-07-2012
www.nayyarENT.com
INNER HAIR CELLS
• Flask shaped
• Flattened or concave
apical surface
• 3-4 linear rows of stereocilia
• Cell bodies are rich in ER,
golgi bodies, mitochondria,
• Synaptic pole at the basal
end
20-07-2012
www.nayyarENT.com
ULTRASRUCTURE OF SUPPORTING
CELLS
• Phalangeal processes: microtubular bundles
• Deiters’ cell cup: Actin- rich core
• Inner phalangeal & border cell membranes:
associated with IHC membranes
• Finger-like projections: interdigitate with afferent
nerve auditory nerve fibres
• Pillar cells: Thick microtubular bundles with radial
feet & arching above
www.nayyarENT.com
20-07-2012
INNERVATION OF ORGAN OF CORTI
• Acoustic information from hair cells is transferred
by the auditory portion of the VIIIth nerve to the
ipsilateral cochlear nuclear complex in the brain
stem
• Composed of afferent fibres from spiral ganglion
neurones
• Types of Neurones: Type I and II
www.nayyarENT.com
20-07-2012
ANATOMY AND ULTRASTRUCTURE OF
THE VESTIBULAR ORGAN
• Delicate system of membranous ducts containing
sensory epithelia or machanoreceptors
• Important for the sense of gravity and balance
• Sensory epithelium located in the 3 ampullae,
semicircular canals and in the maculae of saccule
and utricle
www.nayyarENT.com
20-07-2012
FUNCTIONS OF HUMAN VESTIBULAR
ORGAN
Human Vestibular
Labyrinth Function
Receptor for
Gravitation &
other Linear
Accelerations
Receptor for
Angular
Accelerations
20-07-2012
Regulates
Tonus of Body
Musculature
www.nayyarENT.com
UTRICLE
•
•
•
•
•
Oblong & irregular; superior to the saccule
Slopes anteriorly upwards at an angle of 30 degrees
Macula utriculi lies in a horizontal plane
Mean area: 4.30 mm²
Contains approx. 33,000 hair cells
20-07-2012
www.nayyarENT.com
SACCULE
Hook shaped
Lies virtually in a vertical position
Mean area of saccular macule: 2.4 mm²
Contains approx.18,000 hair cells
Overlying the neuroepithelium is a calcareous
material consisting ‘otoconia’
• Partially anchored in a gelatinous substance
forming otoconial membrane
• Hair processes of sensory cells project into it
•
•
•
•
•
www.nayyarENT.com
20-07-2012
www.nayyarENT.com
20-07-2012
OTOCONIAL LAYER
• Gelatinous layer, a subgelatinous space and
otoconia
• Consists of an organic protein matrix along with
inorganic calcium carbonate crystallized in the form
of ‘calcite’
• Secreted from apical cytoplasm of adjacent
supporting cells with CA
• Degenerative changes with aging & disease
• Otoconial turnover occurs with the help of ‘dark
cells’
www.nayyarENT.com
20-07-2012
SRUCTURE AND FUNCTION OF THE
AMPULLA AND CUPULA
• Superior opening
of horizontal &
superior
semicircular
canal, and
inferior opening
of posterior
canal widen to
form Ampulla
20-07-2012
www.nayyarENT.com
www.nayyarENT.com
20-07-2012
VESTIBULAR SENSORY
CELLS
TYPE I CELLS:
• Flask shaped
• Surrounded by nerve
chalice
• Collateral extensions on
Type II cells
TYPE II CELLS:
• Synapse with the
collaterals & with the
membranes of the
chalices
• Cylindrical
20-07-2012
www.nayyarENT.com
VESTIBULAR NERVE
• Contains approx. 18,000 afferent fibres
• Vestibular ganglion or Scarpa’s ganglion consist of
bipolar neurons
• Consists superior & inferior groups of cells associated
with superior & inferior vestibular nerve.
• Nerves contain both large & small fibres
• Vestibular & cochlear nerves merge in the IAM
• Human vestibular nerve contains efferent fibres
supplying both the cochlear & vestibular sensory
organs
www.nayyarENT.com
20-07-2012
VASCULAR SUPPLY OF LABYRINTH
www.nayyarENT.com
20-07-2012
THANK YOU
For more presentations, visit
www.nayyarENT.com
www.nayyarENT.com
20-07-2012