1. Anatomy of Ear & Mastoid

8/9/2019 1. Anatomy of Ear & Mastoid

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Anatomy of Ear

& Mastoid

Dr. Vishal Sharma


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Embryology


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External ear: Pinna / auricle External auditory canal

Middle ear cleft: Eustachian tube

ym!anic ca"ity #middle ear$

Mastoid air cell system

%nner ear #labyrinth$: ochlea

Vestibule

Semicircular canals

Parts of ear


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External Ear


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External auditory canal

'( mm long) *ateral +/, artilaginous#- mm$:u!

bac medial. Medial '/, 0ony #+1 mm$:do2n

for2ard medial. Pinna !ulled u! bac lateral

to straighten external auditory canal.

3nly cartilaginous sin has hair follicles: furuncle

artilaginous fissure of Santorini& bony foramen

of 4usche: !assage of infection to and from

!arotidgland


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5er"e su!!ly of E.A..


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Middle ear cleft

onsists of:

Eustachian tube

ym!anic ca"ity #middle ear$

Aditus

Mastoid air cell system

De"elo!s from tubo6tym!anic recess


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Middle Ear


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ym!anic membrane

Pearly 2hite semi6translucent membrane

3bli7uely !laced at 889to floor

' !arts: !ars tensa and !ars flaccida

, layers of !ars tensa:outer e!ithelial middle

fibrous & inner mucosal

;ibrous layer disorgani


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im!ani or ettle drum


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http://www.bartleby.com/107/230.html


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http://www.bartleby.com/107/230.htmlhttp://www.bartleby.com/107/230.html


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3tosco!ic "ie2


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1. E!itym!anum:Bounded laterally by scutum + pars

flaccida & medially by bone above tympanic part of

facial nerve2. Mesotym!anum:Middle ear cavity lying opposite

pars tensa & bony tympanic annulus

3. 4y!otym!anum:Middle ear cavity below level of

bony tympanic annulus

4. Posterior tym!anum:Middle ear cavity beind

bony tympanic annulus

!. Anterior tym!anum or Pro6tym!anum:Middle ear

cavity in front of bony tympanic annulus


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>alls of middle ear

=oof:"egmen tympani# middle cranial fossa

;loor:$ugular bulb# carotid artery

Anterior:"ensor tympani# %" orifice# carotid artery

Posterior:ditus# fossa incudis# pyramidal eminence#

facial recess# sinus tympani

*ateral:"ympanic membrane# scutum

Medial:'romontory# oval window# round window#

lateral ())# facial nerve *tympanic part


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*ateral 2all

Membranous:

a. ym!anic membrane

0ony

a. *ateral attic 2all abo"e !ars flaccida #Scutum$

b. *ateral 2all of hy!otym!anum


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Posterior 2all

ditus ad antrum

,ossa incudis for sort process of incus

Bulge produced by lateral semicircular canal

'yramidal eminence for stapedius tendon

Bulge produced by vertical part of facial nerve

(inus tympani

,acial recess


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0oundaries:

- Su!erior:Ponticulus

- %nferior:Subiculum

- *ateral:Mastoid Segment of ;acial 5er"e

- Medial:Posterior semicircular canal

%t e"ades direct surgical "isuali


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Anterior 2all

horda tym!ani ner"e exits "ia canal of 4uguier

anal for tensor tym!anion to!

Eustachian tube o!eningbelo2

%nternal carotid arteryis related inferiorly


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t t f iddl


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ontents of middle ear

Air

, ossicles:malleus incus and sta!es

' muscles:tensor tym!ani & sta!edius

' ner"es:chorda tym!ani & tym!anic !lexus

Mucosal folds & ligaments

0lood "essels


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Eustachian ube


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Anatomy

,1 mmlong in adults

Directed anteriorly inferiorly & mediallyfrom

anterior 2all of M.E. forming angle of (89

2ith

hori


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P t


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Parts

*ateral +/,is bony

Medial '/,is fibro6

cartilaginous. ?unction b/2 ' !arts

is isthmusnarro2est

!art of Eustachian

ube.

Anatom of medial '/,rd


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Anatomy of medial '/,rd

artilage !late lies

!ostero6medially &

consists of medial

lateral laminaese!arated

by elastin hinge. ;ibrous

tissue 3stmann@s fat

!adlie antero6laterally.


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Adult "s hild # B yr$


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Adult "s. hild # B yr$

; ti


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;unctions

+. Ventilation & maintenance of atmos!heric

!ressure in middle earfor normal hearing

'. Drainage of middle ear secretions into

naso!harynxby muco6ciliary clearance

!um!ing action of Eustachian tube & !resence

of intra6luminal surface tension

;unctions


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;unctions

,.Protection of middle ear from:

- Ascending naso!haryngeal secretions due

to narro2 isthmus & angulation bet2een '!arts of E.. at isthmus

- Pressure fluctuations

- *oud sound coming through !harynx


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%nner Ear


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%nner 4air ells 3uter 4air ells


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,899 +'999

Single ro2 hree or four ro2s

;las6sha!ed ylindrical

Primarily afferent Primarily efferent

ransmit auditory stimuli Modulate inner hair cell

=esistant to damage Vulnerable to damage


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Vestibular 4air ells


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Vestibular 4air ells


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em!oral 0one


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MacE2en@s riangle


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g

Su!erior:su!ramastoid crest Anterior:!ostero6su!erior margin of bony

external auditory canal o!ening

Posterior:tangent dra2n to mid6!oint of

!osterior 2all of external auditory canal

ontains s!ine of 4enle

Mastoid antrum lies +'6+8 mm dee! to triangle


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rautmann@s triangle


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g0oundaries

(uperiorly6superior petrosal sinus

'osteriorly6sigmoid sinus

nteriorly6solid angle *semi7circular canals

'atway to posterior cranial fossa from mastoid

cavity & vice versa

Mastoid cells


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entral grou! Accessory grou!

Mastoid antrum S7uamous

Peri6antral 3cci!ital

Peri!heral grou! Styloid Dural Peri6tubal

Sino6dural ygomatic

Peri6sinus Petrous a!ex

i!

=etro6facial


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han ou


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1. Anatomy of Ear & Mastoid

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