Post on 13-Apr-2017
EAR AND AUDITORY PATHWAY
Maj Rishi PokhrelDept of Anatomy
NAIHSwww.slideshare.net
• One structure of human body 0.1 mm thick
and derived from all 3 germ layers?
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3Cochlea Sec tympanic membrane
Promontory
Middle ear
Stapes
Semicircular canal
Vestibule of inner ear
THREE PARTS OF EAR
Ext auditory meatusTympanic membrane
External ear
EXTERNAL EAR
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• Pinna• External auditory meatus
PINNA• Concha• Helix• Antihelix• Scaphoid fossa & triangular
fossa• Tragus• Antitragus• Intertragic notch• Lobule
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EXTERNAL EAR
EXTERNAL AUDITORY MEATUS
Extends from bottom of concha to TM (Length: 25 mm)
Parts– Cartilaginous: lateral 1/3rd
– Bony: medial 2/3rd
Bends– B/T lateral 1/3rd & medial 2/3rd
– 5 mm from tympanic membrane
Direction – Backwards & medially
Epithelium (skin)– Adherent to bone & cartilage
– Ceruminous glands
– Secretions prevent entry of bacteria6
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Nerve supply• ATN (V3)
• Great auricular (C2,3)
•Lesser occipital (C2)
•Facial
•Vagus
•Motor- Facial
Blood supply•Post auricular
•Superficial temporal
•Ant tympanic
•Deep auricular
TYMPANIC MEMBRANE
Size
Diameter – 1cm
Thickness – 0.1 mm
Position– Lie obliquely 55 deg to EAM
– Faces downward, forward & laterally
Umbo– Concavity due to attachment of
handle of malleus
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TYMPANIC MEMBRANESubdivisions
– Pars flaccida (Shrapnel’s membrane)
• between folds
• lax area
– Pars tensa• Rest of the membrane
• tense due to
– attachment of handle of malleus
– radiating fibres of intermediate layer
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PF
Pars Tensa
AMF
PMF
Line of attach of handle of malleuson medial surface
TYMPANIC MEMBRANE
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SurfacesLateral surface
• Concave, directed down, forward & laterally
Medial surface• Convex, maximum at umbo
• Handle of malleus attached here
• Chorda tympani is medial to handle of malleus
TYMPANIC MEMBRANEStructure
From lateral to medial– Outer cuticular layer: stratified squamous nonkeratinized epithelium
– Intermediate fibrous layer: Outer radiating, inner circular fibres
– Inner mucous layer: columnar epithelium; patchy ciliated
Handle of malleus & chorda tympani lie b/t mucous & intermediate fibrous layer
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Outer cuticular layer
Middle fibrous layerInner mucous layer
Deep circularfibres
SuperficialRadiating fibres
Pars flaccida
Tegmen tympani
Tensor tympani
Petrotympanic fissure
Anterior canaliculus
Chorda tympani
Tympanic membrane
Handle of malleus
Processuscochleariformis
Aditus
LATERAL WALL OF LT MIDDLE EAR WITH CONTENTS
TYMPANIC MEMBRANENerve supply
– Lateral surface
• ATN
• Vagus (auricular br)
– Medial surface
• IX CN (tympanic br)
• Chorda tympani
Blood supply– Deep auricular
– Anterior tympanic
– Posterior auricular: stylomastoid br 13
CLINICAL ANATOMY
• ASOM– Pus discharged laterally
• Myringotomy• Incision at posteroinferior quadrant
–Prevent damage to chorda tympani–Rich blood supply: healing faster
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MIDDLE EAR
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Canal for T T
Auditory tube
Aditus to antrum
Mastoid antrum
Mastoid cells
Mastoid process
A P
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Left ear: TM removed
Roof
Floor
Medial wall
Antwall
Postwall
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ROOF
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Petrous temporal
Formation – Tegmen tympani: thin bony plate of petrous temporal
• Separates tympanic cavity from MCF
• Pierced by lesser & greater petrosal nerves
Applied – If unossified: spread of infection to meninges
FLOORFormation
– Floor of jugular fossa (posteriorly)– Posterior wall of ascending part of carotid canal (anteriorly)- Tympanic Canaliculus for tympanic br of IX CN
Applied– Spread of infection to IJV: thrombosis
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Epitympanicrecess
Aditus
Auditory tube
ICA
Sup bulb of IJV
VII CN
ANTERIOR WALL
• Shortened by approximation of roof & floor
• Anteriorly shows posterior wall of carotid canal
• Canal for • Tensor tympani (above)
• Auditory tube (below)
• Processus trochleariformis• Bony shelf extends back on
medial wall & turns laterally; pulley for tensor tympani
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POSTERIOR WALL• Wider above than below
• Aditus to mastoid antrum
• Facial canal
• Pyramid: tendon emerges from apex
• Posterior Canaliculus of chorda tympani
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MEDIAL WALL
Promontory: due to basal turn of cochlea
– Tympanic plexus (IX CN) lies over promontory
Oval window (fenestra vestibuli )
– behind & above promontory
– closed by base of stapes & annular ligament
Round window (fenestra cochleae )
– below & behind promontory
– closed by secondary TM
Facial canal: above & behind promontory
– oblique part, run back & down above oval window
Prominence of lateral semicircular canal– above facial canal
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Left ear: TM removed
Medial wall
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MEDIAL WALL
LATERAL WALL• Tympanic Membrane
• Epitympanic recess
– Part above tympanic cavity
– Upper half of malleus
– Greater part of incus
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MIDDLE EAR: COMMUNICATIONS
• Anterior wall : auditory tube
• Posterior wall: mastoid antrum
• Medial wall : inner ear
• Lateral wall shows : tympanic membrane
• Roof and floor: none
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EAR OSICLES
MALLEUSHead
In epitympanic recess
Post surface: facet for incus- Incudomalleal joint (saddle)
NeckAgainst pars flaccida
Chorda tympani cross medial to neck
• HandleProject down & back till umbo
Processes:
lateral pr: Upper end, handle & lat pr attached to fibrous layer of TM, malleolar folds
Anterior pr: attachment of ant lig of malleus
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INCUS
Body• In epitympanic recess
• Articulates anteriorly with head of malleus
Short process• Lig attached to fossa incudis (post wall of TC)
Long process• Hook medially, articulate with stapes
• Incudostapedial joint: ball & socket
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STAPES• Head
– Articulates with lenticular nodule of incus• Neck
– Stapedius attached to back of neck• Ant & post limbs• Foot plate
– anchored to fenestra vestibuli by annular lig– syndesmosis
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TENSOR TYMPANIOrigin
• Bony & cart part of AT, becomes tendon, hooks around processus trochleariformis
Insertion• Handle of malleus: upper part
Nerve supply• Nerve to medial pterygoid
Actions• Pull handle of malleus, TM concave,
makes tense• Increase tight adhesion of footplate to
fenestra vestibuli– dampens sound
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STAPEDIUSOrigin
• Interior of hollow pyramidInsertion
• Back of neck of stapesNerve supply
• Facial nerveActions
• Retract neck of stapes from fenestra vestibuli• Paralysis: hyperacusis
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CLINICAL ANATOMY
Normal TM Wax
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PERFORATION OF TM
Perforation
MYRINGOTOMY
MYRINGOTOMY & SYRINGING
EAR SYRINGING
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OTITIS MEDIA
Serous otitis mediaASOM
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OTITIS EXTERNA
TYMPANOSCLEROSIS
Internal ear
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Auditory pathway
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Auditory pathway
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Olfactory pathway
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Olfactory reflexes
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