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

........,_

© 2011 Pearson Education, Inc.

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)

- --<..._LI...J....'

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