HISTOLOGY OF THE
EAR
THE EAR
Ear
Sensory organ functions as an auditory system for
sound perception and as a vestibular system for
balance
General Structure
External Ear
Middle Ear
Internal Ear
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External Ear
Pinna
Auricle
Elastic cartilage except in auricle lobule
Covered by hair-bearing skin hair follicles, sweat
gland and sebaceus gland
Function To collect and amplifies sounds
External Acoustic Meatus
An air-filled tubulae space 25 mm to tympanic
membrane
Lined by skin hair follicles, sebaceous gland &
ceruminous glands
The outer 2/3 elastic cartilage
The inner 1/3 temporal bone
Middle Ear
Tympanic Membrane
oval, grayish
3 layers
Outer layer covered by
skin, stratified squamous
epithelium, no glands, no
hair
Middle layer
Fibrocollagenous support
tissue
Inner layer lined by low
cuboidal epithelium
Auditory ossicles
3 bones malleus, incus, stapes
2 muscles m tensor timpany & m. stapedius
Convert the sound waves to mechanical vibration in perilmfe of the
internal ear
Mastoid air cells
An air-filled spaces in the mastoid bone
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Tympanic cavity
= Middle ear cavity
An air-filled space lined by low cuboidal epithelium
Communicates with mastoid air cells
Auditory tube (eustachian tube)
Connects the middle ear to
nasopharynx
A narrow channel 3.5 cm long
Lined with cilliated pseudostratified
columnair epithelium 1/5 composed
of goblet cells
Ventilating the middle ear
Equalizing the pressure ot the
middle ear with atmosphere pressure
Internal Ear
Consists of :
2 labyrinthine compartments
Bony labyrinth
Membranous labyrinth
3 fluid-filled spaces
Endolymphatic space
Perilymphatic space
Cortilymphatic space
Bony Labyrinth
Composed of 3 cavities
vestibule, semicircular canals,
cochlea
Lined by periosteum, filled by
perilymph
Vestibule
Oval
Oval window
Semicircular canals
3 canals anterior, posterior &
lateral
Expanded at the end of each
canals close to the vestibule
ampulla
Cochlea
Contains 3 spaces
vestibular cavity (scala
vestibuli), cochlear duct
(scala media) & tympanic
cavity (scala tympani)
wound in a spiral shape
The central spiral of bone
within the cochlea
Modiolus
At the apex the vestibular
& tympanic cavity connect
at an opening
Helicotrema Helicotrema
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Membranous Labyrinth
Vestibular labyrinth
3 semicircular ducts
Utricle & saccule
Thin wall, transparent
Semicircular ducts
3 ducts, expand at the end ampulla
A raised mass of epithelial tissue in
ampulla crista ampullaris
contains of sensory & supporting
cells
A gelatinous mass of extracellular
material covering the crista
cupula
Utricle
Ends of semicircular
ducts
Lateral wall macula of
utricle
Saccule
Utriculosaccular duct
connect the utricle &
saccule
Endolymphatic duct
saccule and
endolymphatic sac
Reuniens duct saccule
with cochlear duct
Medial wall macula of
saccule
Macula
Contains of sensory hair
cells & supporting cells
2 types of sensory cells
Type 1 hair cells
Type 2 hair cells
The sensory & supporting
cells covered by a
gelatinous mass of
extracellular molecules
otolithic membrane
Detect the gravity and
static position
Cochlear Labyrinth
Contains the cochlear ducts, filled with endolymph
Divides the cochlear canal into 3 compartments : Scala media, scala
vestibuli & scala tympani
Scala media is a triangular space, attached to osseous spiral lamina
The upper wall of scala media Reissners (Vestibular) membrane
The lateral wall of scala media Stria vascularis
The lower wall Basilar membrane
The spiral organ of corti rests on the basilar membrane & is overlain by the
Tectorial membrane
Tectorial membrane
Attached medially to the
modiolus
Lateral edge attaches to
the organ corti by
stereocilia of the hair
cells
Formed from
extracellular material
Organ of Corti
Composed of epithelial support cells
and sensory hair cells
Medially it rests on osseous spiral
lamina, laterally on the basilar
membrane
2 groups of hair cells
Inner hair cells & Outer hair cells
separated by the inner tunnel
(tunnel of corti)
The hair cells are surrounded by
epithelial support cells
Pilar cells surround & support
the inner tunnel
Phalangeal cells support the hair
cells
