Middle and inner ear 15416
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Transcript of Middle and inner ear 15416
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EAR
1st part ……………external ear
2nd part….................middle ear
3rd part……………..inner ear
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EXTERNAL EAR
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ANATOMY OF MIDDLE EAR CLEFT
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THE MIDDLE EAR CLEFT
The middle ear cleft consists of the
tympanic cavity,
Eustachian tube and
mastoid air cell system.
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THE TYMPANIC CAVITY
Divided into threecompartments
Epitympanum
Mesotympanum
Hypotympanum
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Walls of the Tympanic Cavity
It has 6 walls,
I. Membranous wall (lateral wall)
II. Tegmental wall (roof)
III. Jugular wall (floor)
IV. Carotid wall (anterior wall)
V. Labyrinthine wall (medial wall)
VI. Mastoid wall (posterior wall)
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THE ROOF
Tegment tympani
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It is formed by both the petrous and squamous portions ofthe temporal bone
The petrosquamous suture line, which does not closeuntil adult life, can provide a route of access for infectioninto the extradural space in children
Veins from the tympanic cavity running to the superiorpetrosal sinus pass through this suture line
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THE FLOOR
The dome of thejugular bulb
Tympanicbranch of theglossopharyngealnerve
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THE ANTERIOR WALL
Lower-third
carotid artery
Middle-third
A)tympanic orifice of the
Eustachian tube
B)canal for the tensor
tympani muscle
Upper-third
pneumatized
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THE POSTERIOR WALL
The aditus of mastoid antrum
Fossa incudis
Pyramid
Bony facial canal(vertical part)
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THE LATERAL WALL
Formed by the
Bony lateral wall ofepitympanum
Tympanic membrane
Bony lateral wall ofhypotympanum
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THE MEDIAL WALL
The promontory
Oval window
Round window
Oblique part offacial canal
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THE CONTENTS OF THE TYMPANIC CAVITY
The tympanic cavity contains the
Ear ossicles – malleus, incus and stapes
Muscles – Stapedius, Tensor tympani
The chorda tympani and
The tympanic plexus
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EAR OSSICLES
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THE MALLEUS (the hammer)
Largest, 9 mm in length
The head lies in theepitympanum
The head of the malleusarticulate with the bodyof the incus by a synovialjoint
The lateral processprominent landmark onthe tympanic membrane
Body
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THE INCUS (the anvil)
Has a body and two processes
The body lies in the epitympanum
The short process lie in the fossaincudes
The long process descends intothe mesotympanum
Lenticular process articulates withthe head of the stapes.
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THE STAPES (the stirrup)
Shaped like a stirrup
Consists of a head, neck, theanterior and posterior crura and afootplate.
The stapedius tendon inserts intoneck
The two crura arise from lower partof the neck
Footplate lies in the oval windowwhere it is attached to the bonymargins by the annular ligament
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THE STAPEDIUS MUSCLE
Arises from wall of conical cavity within pyramid
Attaches to neck of stapes
Helps to dampen loud sound,
Preventing noise trauma
Supplied by branch of Facial Nerve
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TENSOR TYMPANI MUSCLE
● Arises from a)bony canal above ET b)cartilagenous part of ET c) greater wing of sphenoid
● Attaches to neck of malleus
● Tenses tympanic membrane
● Supplied by branch of Mandibular Nerve
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THE MASTOID AIR CELL SYSTEM
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The mastoid antrum air-filled sinus in the petrous part oftemporal bone.
It communicates with the middle ear by the aditus.
Antrum is well developed at birth.
Volume = 2 ml (adult).
The medial wall relates to the posterior semicircular canal.
More deeply and inferiorly is the dura of the posterior cranialfossa and the endolymphatic sac.
The roof of the mastoid antrum and mastoid air cell spaceform the floor of the middle cranial fossa.
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MacEwen's triangle
– Temporal line
– Posterosuperior segment of bony EAC
– a tangent through the posterior border of EAC
Normally lining of the mastoid is a flattened, nonciliatedepithelium without goblet cells or mucus glands.
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THE BLOOD SUPPLY OF THE TYMPANIC CAVITY
Arise from both the internal and external carotid system.
The overlap is extensive and great variability is present.
Anterior tympanic
Stylomastoid
Maxillary
Posterior auricular
Middle meningeal
Ascending pharyngeal
Artery of pterygoid canal and internal carotid arteries.
The anterior tympanic and stylomastoid arteries arethe biggest.
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Venous drainage
Pterygoid plexus
Superior petrosal sinus
Lymphatic
Retropharyngeal
Parotid lymph node
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Applied anatomy
Facial nerve injury
Hyperacusis
Eustachian catarrh
Encephalitis
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Facial nerve injury
Hyperacusis
Eustachian catarrh
Encephalitis
Applied anatomy
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Otitis Media Otitis media is an infection
or inflammation of the
middle ear
This inflammation often
begins when infections that
cause sore throats, colds, or
other respiratory or
breathing problems spread
to the middle ear
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Otosclerosis
Otosclerosis is the abnormal
growth of bone of the middle
ear. This bone prevents
structures within the ear from
working properly and causes
hearing loss
Symptoms: Severe tinnitus,
recurring auditory memories,
and frequent vertigo
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The inner ear is called as labyrinth, from the complexity of its shape.
It consists of two parts:
1. The osseous labyrinth
2. The membranous labyrinth
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The Osseous Labyrinth (labyrinthus osseous)
Consists of three parts:
The vestibule,
semicircular canals
cochlea.
lined by periosteum.
Contain a clear fluid, perilymph, in which the membranous labyrinth is situated
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The Vestibule (vestibulum)
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The Bony Semicircular Canals 3 in number
superior, posterior, and lateral,
Above and behind the vestibule.
Unequal in length
They open into the vestibule by five orifices, one of the apertures being common to two of the canals
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THE COCHLEA
Resemblance to a common snail-shell
Anterior part of the labyrinth
It is conical in form, and placed almost horizontally in front of the vestibule
Apex
Base
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Membranous labyrinth consists of
Cochlear duct,
Two sacs, utricle and saccule
Three semicircular ducts
Endolymphatic duct & sac
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Blood supply of labyrinth Mainly by internal auditory a. (branch of AICA - branch of
basilar a.)
Internal auditory artery divides into
1. Anterior vestibular artery
Supplies utricle ,superior & lateral SCC
2. Common cochlear artery
Main cochlear artery(80%)-supplies cochlea
Vestibulocochlear artery
1. Post vestibular A.-supplies saccule & post SCC
2. Cochlear branch –supplies to cochlea4/15/2016 43
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Venous drainage Mainly by:
Internal auditory vein
Vein of cochlear aqueduct
Vein of vestibular aqueduct
These Drain into inferior petrosal and sigmoid sinuses.
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Conductive Hearing Loss
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Sensorineural Hearing Loss
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LabyrinthitisInflammation of the semi-circular canals give you a
sense of motion when you’re not moving = VERTIGO
(dizziness) or LABYRINTHITIS
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Meniere’s Disease Vertigo, balance problems,
Loss of low pitches
Tinnitus
Fluctuating hearing loss
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THANK YOU