ANATOMY AND PHYSIOLOGY OF THE EXTERNAL EAR, MIDDLE EAR AND INNER EAR
NS47 2014 - Inner Ear
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Transcript of NS47 2014 - Inner Ear
Temporal bone, Inner ear, IAM, CN VII & VIII
CLASS: JC3 2014 COURSE: Neuroscience CODE : NS 47LECTURER : Dr. Latifa NishatDATE : 10/11/2014 1330 -1430
TEMPORAL BONE, INNER EAR,IAM, VII & VIII
CLASS: JC3 2013 COURSE: NEUROSCIENCE CODE : NS 44LECTURER : DR ROHANA O’CONNELL DATE : 31/10/2013 1330 -1430
Learning outcomes• Parts of temporal bone, its
openings and cavities• Structure of inner ear organs of
balance and hearing• Eighth cranial nerve and its
central connections• Seventh cranial nerve: its nuclei,
components and relation to temporal bone
Temporal bone
Temporal bone
I I I I I I I I I I I
,>I I I I I I I I I
II
Squamous part
Groove for superior petrosal sinusArcuate eminenceGroove for greater petrosal nerveGroove for lesser petrosal nerve
Groove for sigmoid sinus
Temporal bone
Groove for greater petrosal nerve
Geniculum of facial nerve
Cochlear nerve
Facial nerve (VII)Internal
acoustic opening/meat
usVestibulocochl
ear nerve (VIII)
Vestibular nerve
Temporal bone
Anterior semicircular canal
Lateral semicircular canalCopyright 0 2005 by Elsevier,Inc
Cochlea
Posterior semicircular canal
Vestibulocochlear nerve (VIII)
Temporal bone
Facial nerve
1. Motor fibres2. Sensory fibres3. Parasympathetic fibres4. Taste fibres
Facial nerve
Facial nerveGeniculate ganglion Facial nerve
(VII)Internal acoustic meatus
Middle ear
Greater petrosal nerve (GPN)
Nerve to stapedius
muscle
Chorda tympani
Stylomastoid foramen
Facial nerve
Nucleus abducens
Internal capsule
Trigeminal-Spinal Nucleus and Tract
Medial lemniscus
Internal capsule
Nucleus VII
VII
VII
• SVE (Special Visceral Efferent) — Motor to striated muscles derived from the 2nd branchial arch
• GVA (General Visceral Afferent) — Sensory from visceral touch, temperature, and pain
• SVA (Special Visceral Afferent) — Taste• GVE (General Visceral Efferent) —
Autonomic innervation to mucosal, lacrimal, and salivary glands
• GSA (General Somatic Afferent) — Sensory from somatic touch, temperature, and pain.
Facial nerve (Functional components)
Motor nucleus• Pons• Special Visceral Efferent• Branchiomotor: supply all of the
muscles derived from second branchial arch
• In the middle ear : stapedius• Extratemporal: muscles of facial
expression, buccinator, platysma, posterior belly of digastric
Facial nerve nuclei
Superior salivatory nucleus (nervus intermedius)• Pons• General visceral efferent/Parasympathetic
• Pterygopalatine ganglion• Submandibular ganglion
• GSPN (greater superficial petrosal nerve):• Secretomotor to lacrimal, nasal, palatine
glands• Also receives taste sensation from palate
• Chorda tympani:• Taste from anterior 2/3rd of the tongue
Facial nerve nuclei
Nucleus of tractus solitarius• Medulla oblangata• Special visceral afferent• Taste from tongue (chorda
tympani) and palate (greater petrosal)
• Sensory sense – trigeminal (spinal nucleus) - eardrum and canal
Facial nerve nuclei
Guess the functional component?
• Greater Superficial Petrosal Nerve (GSPN)
1. 2. 3. • Stapedial Nerve
1. • Chorda Tympani Nerve
1. 2. • Posterior Auricular Nerve
1. 2. • Facial Nerve (terminal
branch)1.
GVA: Light touch, temperature, and pain sensation from thesoft palate via the GSPNSVA: Taste from the hard and soft palate via the greater superficial petrosal nerve (GSPN)Taste from the anterior 2/3 of the tongue via the chordatympani nerve.GVE: GSPN transmits preganglionic fibers to the pterygopalatine ganglion. From the pterygopalatine ganglion postganglionic fibers cause ipsilateral lacrimation and mucus secretions of the nasal and oral cavities.The GVE component of the facial nerve transmits preganglionic fibers to the submandibular ganglion via the chorda tympani nerve. From the submandibular ganglion postganglionic fibers innervate the submandibular and sublingual glands, causing salivation
Facial nerve (Functional components)
GSA: Touch, temperature, and pain sensation from part of the external acoustic meatus via the posterior auricular nerve.SVE:1. Stapedius muscle -- dampens movement of the
ossicles(inserts on stapes of middle ear)
2. Posterior auricular muscle -- posterior movement of pinna
3. Stylohyoid muscle -- elevates hyoid bone4. Posterior belly of digastric -- elevates hyoid
bone, depresses mandible5. Muscles of facial expression -- blinking,
smiling, frowning, facial movements
Facial nerve (Functional components)
Inner ear and
Vestibulocochlear nerve
Three anatomical regions of the ear:the external ear,the middle ear,and the inner ear
The visible portion of the ear; collects and directs sound waves toward the middle ear
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External ear Middle ear Inner earAn air-filled chamber;is connected to the nasopharynx by the auditory tube
Site of sensory organs for hearing and equilibrium; receives amplified sound waves from the middle ear
Tympanic cavity
To nasopharynxAuditory tube(pharyngotympanic tube/Eustachian tube
Vestibulocochlear nerve (VIII)
Tympanic membrane(Tympanum or eardrum)
External acoustic meatus
Auricle
Semicircular
canalsPetrous part of temporal
boneFacial nerve (VII)
Bony labyrinth
Inner ear• The receptors for balance and hearing are
located within fluid-filled chambers and tubes that form the membranous labyrinth
• The fluid of the membranous labyrinth is called endolymph
• The membranous labyrinth is surrounded and protected by a shell of bone called the bony labyrinth
• The contours of the bony labyrinth closely resemble the membranous labyrinth
• The space between the membranous and bony labyrinth is filled with a fluid called perilymph that closely resembles CSF
Bony labyrinth
Three regions:• Vestibule• Semicircular
canal• Cochlea
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into)
The regions & functions of membranous labyrinth
The membranous labyrinth is filled with endolymph and surrounded by perilymph in the bony labyrinth
Vestibular complex (equilibrium)The vestibular complex is the part of inner ear that provides equilibrium sensations by detectingrotation, gravity, and linear acceleration Cochlear duct (hearing)
Movement of the stapes at the oval window generates pressure wave that stimulates hair cells at the specific locations along the length of the cochlear duct
Semicircular ductThe three semicircular ducts monitor rotational movementsin three different planes
Utricle & sacculeThese chambers containreceptors sensitive to head position relative to gravity; they also responds to linear acceleration
Semicircular canals (SCC) • The anterior, posterior and lateral
SCC are designed to detect rotation
• Each SCC contains a semicircular duct (SCD)
• SCD have dilated ends known as ampulla
• Sensory area in ampulla is known as Crista
• Cupola : gelatinous mass that acts on hair cells
cupola
Crista
Membranous labyrinth
Endolymph
Cupula
Hair cells
Supporting cells
(c) Ampulla, sectional view
Sensory
nerve
Semicircular canals (SCC)
• The hair cells are the receptor cells.
• They are associated with supporting cells.
• The apical surface of the hair cell has long microvilli called stereocilia (hence, "hair" cell) and one cilium called a kinocilium.
• The kinocilium and stereocilia are embedded in a cupola which nearly fills the space within the ampulla.
Semicircular canals – Hair cells
Rotational movements in different planes are detected by the mechanical distortion of the stereocilia as fluid moves within the
semicircular ducts
Semicircular canals (SCC)
Utricle and saccule
• The utricle and saccule are interconnected membranous sacs of the membranous labyrinth found in the vestibule
• The endolymph of the utricle is confluent with that of the semicircular ducts and the endolymph of the saccule is confluent with that of the cochlear duct
• The utricle and saccule are interconnected by a narrow endolymphatic duct that ends in a blind pouch called the endolymphatic sac
Helicotrema of cochlea
- - - - . . :
Vestibule
Pharyngotympanic/auditory tube
Otic capsule
Cochlear aqueduct
Scala tympani
Cochlear duct
Scala vestibuli
Ductus reuniens
Anterior semicircular canal & ductPosterior semicircular canal
& duct
Lateral semicircular canal & duct
Otic capsule
Common bony & membranous limbs
Ampullae Dura
mater
Utricle Saccule
Endolymphatic duct in vestibular aqueductEndolymphatic
sac
Stapes in oval (vestibular) window Incus Malleu
s Tympanic cavity
umboExternal acoustic
meatus Tympanic
membrane Round (cochlear) window closed by secondary tympanic membrane
Inner ear - parts
• Both the utricle and saccule contain hair cells similar to those found in the semicircular canals
• In each sac the hair cells are concentrated on a oval spot in the wall called a macula ("spot")
• The kinocilia and stereocilia of the hair cells are embedded in a gelatinous mass that has crystals of calcium carbonate embedded on its surface
• This gelatinous mass with its crystals is called an otolith and the crystals are called statoconia
Utricle and saccule
Utricle and saccule – Macula and statoconia
Otolith
Gelatinous matrix
Supporting cell
(a ) Macula of an utric le or saccule Copyright C 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
(b) Crista of an ampulla
Wall of ampulla
Hair cell
Supporting cell
Vestibular complex
The difference in density between the crystals and the gelatinous matrix causes a mechanical distortion of the
stereocilia of the hair cells when the head is tilted or the body experiences acceleration. Hence, the hair
cells detect the position of the head in space and linear acceleration.
Utricle and saccule – Macula & statoconia
Vestibular connections
• The first-order vestibular afferents have their cell bodies in the vestibular (Scarpa’s) ganglion, which is found at the distal end of the internal auditory meatus.
• Their axons travel in the vestibular portion of the 8th cranial nerve through the internal auditory meatus and enter the brain stem at the junction between the pons and the medulla.
• Project to one of the 4 vestibular nuclei
Vestibular nerve
Four 2nd order vestibular nuclei: SLMI (all beneath the floor of the 4th ventricle)Second order neurons go to:1. Vestibulo-spinal tract:
mediate extensor motor neurons, control extensor muscle tone in anti gravity maintenance of posture2. Vestibulo-cerebellum/cerebellar reflex:
through the inferior cerebellar peduncle to the Flocculonodular lobe3. Vestibulo-ocular reflex:
medial longitudinal fasciculus connects brainstem nuclei (occulomotor, trochlear and abducens)
Vestibular nerve
Trochlear nucleusMLF (ascending
fibers)
Abducens nucleus
Semicircular canals: ampullaeUtricle: maculaeSaccule: maculae
SVN
To cerebellum
Lateral vestibulospinal tract
MLF (descending fibers)
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To cervical spinal cord for adjustment of head position To extensor motor
neurons
Occulomotor nuclear complex
Vestibular nerve
CochleaThe cochlea coils about 2.5 turns around a
central hub called the modiolus. The sensory neurons that form the cochlear nerve have their cell bodies in the modiolus in a ganglion called
the spiral ganglion.
Organ of Corti
To round windowSpiral
ganglion(b) Cochlear section, diagrammatic
Apical turn
Tectorial membra
ne
Vestibular
membrane
Middle turn
Modiolus From oval
windowBasal turn
Vestibular duct (scala vestibuli) contains perilymphCochlear duct (scala media) contains endolymph
Tympanic duct (scala tympani) contains perilymphTemporal bone
(petrous part)Vestibulocochlear nerve
Basilar membrane
Cochlear nerve
Cochlea
Organ of Corti• The hair cells that are responsible for
hearing are within the organ of Corti, or spiral organ.
• The organ of Corti rests on a basilar membrane whichseparates the cochlear duct from the tympanic duct.
• The hair cells are arranged in an inner row and outer rows that follow the turns of the cochlear duct.
• The stereocilia (a kinocilium is lacking) of the the hair cells are in contact with an overhanging tectorial ("roof") membrane that is attached to the inner wall of the cochlear duct.
Modiolus
(a)
Tectorial membraneVestibular membrane
Cochlear duct (scala media)
cochlear nerve
(b )
(c )
Copynght C 2006 Pearson Education, Inc., publishing as Beniamin Cummings.
Cochlear duct (scala media)
Vestibular
membrane
Spiral ganglion
Tectorial membraneSpiralganglion Outer hair cells
Innerhair cellsStereocilia
Cochlea - Organ of Corti
The Auditory Pathway
Auditory cortex
Lateral fissure
Auditory nerve
Mid brain
Inferior colliculus
Medial geniculate nucleus
Dorsal cochlear nucleus
Thank you