Histology: Secondary Sentiment Sense Organs - The Ear
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Transcript of Histology: Secondary Sentiment Sense Organs - The Ear
Secondary Sentient Sense Organs
Organ of Hearing
Organ of Equilibrium
Organ of Taste
Lecturer – professor Boronikhina Tatiana Vladimirovna
Secondary sentient sense organs contain neuroepithelial receptor cells
Neuroepithelial cells form synapses with sensory neuron dendrites
Neuroepithelial cells interact with stimuli
generate nerve impulses
transmit impulses to sensory neurons
dendrite°°°°
Hearing Equilibrium Taste
Organ of hearing
receptor field is the spiral organ or organ of Corti is housed in the cochlea of the inner ear
Cochlea
Inner ear is the bony labyrinth in the temporal bone
Cochlea Vestibule
saccule utricle
Semicircular canals (3)
the temporal bone petrous portion
Bony labyrinth houses the membranous labyrinth
bony labyrinth is filled with perilymph membranous labyrinth is filled with endolymph
perilymph and endolymph communicate with CSF in the meningeal spaces
Inner ear receptor fields
hearing and equilibrium receptor fields
reside in the membranous labyrinth are bathed by endolymph
Cochlea
has a broad base and apex is a bony tube that spirals 2.5 times around
the modiolus
Modiolus
is osseous cochlea axis contains nerve fibers projects laterally into the spiral lamina
n. vestibulocochlearis (VIII)
Spiral lamina
consists of two lips upper lip periosteum thickens to form
the spiral limbus contains the spiral ganglion
limbus
spiral ganglion
upper lip
lower lip
Cochlea passages
Scala vestibuli Scala tympani
contain perilymph
Scala media (cochlear duct) contains endolymphSG
Sv
St
Sm
Cochlear perilymphatic passages
Scala vestibuli and scala tympani
communicate with each other
at the helicotrema
Scala vestibuli and scala tympani associate with the middle ear
Scala vestibuli ends at the oval window
is closed by the stapes stapes transmits vibrations to perilymph
Scala tympani
ends at the round window
is closed by connective tissue membrane
auditory ossicles
Scala media is the cochlear membranous labyrinth
Scala media walls vestibular membrane stria vascularis basilar membrane
Vestibular membrane
extends between the spiral limbus and the cochlear wall separates the scala media from the scala vestibuli consists of two layers of endothelial cells
vestibular membrane
Stria vascularis consists of a pseudostratified epithelium
is vascularized by capillaries secretes endolymph and creates its high positive potential rests on the spiral ligament – thickened periosteum of the cochlear bone
stria vascularis
spiral ligament
Basilar membrane
separates the cochlear duct from the scala tympani includes keratin-like fibrils – hearing cords
basilar membrane
upper surface contains the spiral organ
low surface is lined with endothelium
Basilar membrane fibrils vibrate with perilymph
are slender and long near the cochlea apex vibrate in resonance with low-frequency sounds
are thick and short near the cochlea base vibrate in resonance with high-frequency sounds
Spiral organ lies upon the basilar membrane
Phalangeal cells (supporting)
Hair cells (neuroepithelial) stereocilia (hair) are on the apical surface stereocilia are embeded in the tectorial membrane
Pillar cells (supporting) enclose the tunnel filled with endolymph
Tunnel divides the spiral organ in the two cell groups
Outer group is organized in three or more rows
outer phalangeal cells
outer hair cells
Inner group is organized in a single row
inner phalangeal cells
inner hair cells
inner hair cell
Spiral organ inner group cells
Inner phalangeal cells completely surround the hair cells
Inner hair cells are bulbous in shape have stereocilia arranged in a straight line
Spiral organ outer phalangeal cells
surround only the basal portion of hair cells
phalangeal processes form the cuticular plate
Spiral organ outer hair cells
are columnar in shape
have stereocilia arranged in a V-formation
Scanning electron micrograph of the hair cell stereocilia
inner hair cells
outer hair cells
Spiral organ histology
Spiral organ innervation
Sensory bipolar neurons are
in the spiral ganglion
Afferent fibers are sensory neuron dendrites pass in the tunnel form light synapses on the hair cells
Efferent fibers are the brain neuron axons pass in the tunnel form dark synapses on the hair cells
Spiral ganglion sensory neuron axons
form the cochlear division ofn. vestibulocochlearis (VIII)
pass in the modiolus
Hearing
sound waves transmit vibrations on timpanic membrane auditory
ossicles oval window perilymph basilar membrane fibrils
spiral organ
Hair cells are mechanoreceptors
nerve impulse generation results from stereocilia inclination
microenvironment - endolymph tectorial membrane
dendrite
°°°°°°°°dendrite
Hair cell differentiation
Hair cells perceive in the cochlea base – high-frequency sounds in the cochlea apex – low-frequency sounds
outer hair cells – high intensity sounds inner hair cells – low intensity sounds
Organ of equilibrium or vestibular apparatus
receptor fields are the maculae and the cristae are housed in the vestibule and canals of the inner ear
vestibule and semicircular canals
Equilibrium receptor field localization
maculae (2) are in the saccule and utricle cristae (3) are in the ampullae of the semicircular canals
Vestibular macula and crista ampullaris
crista in the semicircular
canal ampulla
macula in the saccule
Macula structure
supporting cells neuroepithelial hair cells otolithic membrane with otoliths
Crista structure
supporting cells neuroepithelial hair cells cupula
Equilibrium neuroepithelial hair cells
are innervated by afferent
and efferent fibers
apical surface contains
50-100 stereocilia and
a single kinocilium
Equilibrium hair cell types
Type I cells are bulbar in shape basal portion surrounded by
a cap-shaped nerve ending
Type II cells are columnar in shape basal portion has bouton nerve ending
Vestibular apparatus innervation
sensory neuron bodies are housed
in the vestibular ganglion
their dendrites innervate hair cells of
maculae and cristae
their axons form vestibular division of
n. vestibulocochlearis (VIII)
Equilibrium hair cells are mechanoreceptors
nerve impulse generation results from stereocilia inclination
dendrites
microenvironment – endolymph cupula otolithic membrane with otoliths
dendrites
dendrite°°°°
Equilibrium hair cell stereocilium inclination
towards the kinocilium away from the kinocilium
cells become excited cells become inhibited
Equilibrium hair cell differentiation
Maculae are sensors of linear accelerations gravity vibrations
Cristae are sensors of angular accelerations
Organ of taste
receptor field consists of the taste bauds taste buds are located on the lateral surface
of lingual papilae
tongue dorsal surface
Lingual papillae are projections of the mucosaon the tongue dorsal surface
Papilla structure: stratified squamous partially keratinized epithelium a central core (primary papilla) – LCT
taste buds occupy the epithelium of the lateral papilla surface
taste bud is an ovoid
intraepithelial structure
Lingual papilla types
filiform papillae are covered by keratinized epithelium
and lack the taste buds
Taste buds are epithelial structures
epithelial cells are arranged around the taste pit taste pore leads to the taste pit
taste pore
Taste bud morphology
taste pore
photomicrograph
electron micrograph
Taste bud cells
supporting cells neuroepithelial cells basal cells (stem cells)
Taste bud neuroepithelial cells are chemoreceptors
Apical cell surface possesses microvilli pass through the taste pore are bathed by saliva contain membrane chemoreceptors for taste molecules
microenvironment - saliva
Taste bud innervation
Neuroepithelial cell basal portion synapses with
afferent and efferent nerve fibres
• chorda tympani of n. facialis (VII)
• n. glossopharyngeus (IX)
• from taste buds of the epiglotis n. loryngeus superior of n. vagus (X)
Sensory neurons of the taste analyzer
are in sensory ganglia associated
with the cranial nerves:
• n. facialis
• n. glossopharyngeus
• n. vagus
Taste bud neuroepithelial cell differentiation
Perception of the taste sensations
bitter
sour (acid)
salt
sweet
Thank you for attention!