4. OUTER EAR
Its functions
Collects sound
Localization
Resonator
Protection
Sensitive (earlobe)
• It has Three main parts:
Pinna(auricle) , External
Auditory Meatus and
eardrum(tympanic mebrane)
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5. Pinna(auricle)
The visible portion that is commonly referred to
as "the ear" ,It consists of cartilege and skin
Helps localize sound sources and directs them
towards the external auditory meatus and on to
the tympanic membrane
• Lymphatics;drain into parotid group,upper deep
cervical and mastoid lymphnodes
• Veins;dain into into external jugular,common
facial vein
• Arteries;posterior auricular branch of external
carotid artery,ant.auricular branch of superficial
temporal and a branch of occipital artery
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6. Auriculotemporal nerve (CN V3): It is a
branch of mandibular division of trigeminal
nerve and supplies anterosuperior part of lateral
surface of pinna including tragusand crus of
helix.
CN VII (facial nerve): It innervates the skin of
lateral concha and antihelix, lobule and
mastoid.
CN X (vagus nerve): Its auricular branch
(Arnold’s nerve) supplies to concha and post
auricular skin.
Greater auricular nerve (C2,3): This nerve of
cervical plexus supplies most of the medial
surface of auricle and posterior part of lateral
surface and the postauricular region.
Lesser occipital nerve (C2): This nerve of
cervical plexus supplies upper part of medial
surface of auricle and postauricular region.
Nerve supply
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7. Is a curved tube about 2.5cm that lies in the temporal bone and leads from the
auricle to the eardrum (tympanic memb)
Near to the exterior of its opening there is a few hairs and specialized
sebaceous(oil)glands called ceruminous glands that secrete cerumen(earwax)
The combination of hairs and cerumen help prevent dust and foreign objects
from entering the ear and cleaning mechanism of ear
NERVE SUPLY
(i) Anterior wall and roof: auriculotemporal (V3) supplies anterosuperior wall
of external auditory canal
(ii) Posterior wall and floor: auricular branch of vagus nerve(CNX) supplies to
inferoposterior external auditory canal.
Posterior wall of the auditory canal also receives sensory fibres of cranial N VII
(facial nerve) through auricular branch of vagus.
External Auditory Meatus
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8. Eardrum(tympanic membrane)
It is a thin,semitransparent partiton between the external auditory canal and
middle ear.
It has two parts :(a) Pars Tensa:
It forms most of tympanic membrane..
Its periphery is thickened to form a fibro cartilaginous ring called the
annulus tympanicus which fits in the tympanic sulcus.
The central part is tented inwards at the level of the tip of malleus and is
called the umbo.
(b) Pars Flaccida (Shrapnel's Membrane)
• This is situated above the lateral process of malleus between the notch of
Rivinus and the anterior and posterior malleolar folds.
It has three layers:
(i) Outer epithelial layer, which is continuous with the skin lining the
meatus. no hairs and glands
(ii) Middle fibrous layer, which encloses the handle of malleus and has three
types of fibres-the radial, circular and the parabolic.
(iii) Inner mucosal layer, which is continuous with the mucosa of the middle
ear
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9. 1. Malleus 2,6
2. Anterior mallear fold
3. Post mallear fold
4. Pars flaccida
5. projection of long process of
incus.
6. Pars tensa
7. Annular ligament.
Tympanic membrane
NERVE SUPPLY
(i) Anterior half of lateral surface:
auriculotemporal(V 3)
(ii) Posterior half of lateral surface: auricular
branch of vagus nerve (CN X) (Arnold’s nerve)
(iii) Medial surface: Tympanic branch of CN
IX glossopharyngeal nerve (Jacobson's nerve).
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10. MIDDLE EAR
It has two main parts:
Auditory ossicles
(transmit and mplify sound
from the tympanic membrane
to the oval window)
Auditory(eustachian)tube(e
qualizes pressure on both
sides of the tympanic
membrane
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11. MIDDLE EAR
The middle ear together with the Eustachian tube,
aditus,antrum and mastoid air cells is called the
middle ear cleft.
its lined with mucous membrane and filled with
air.
Aditus and Antrum: Aditus is an opening through
which the attic communicates with the antrum.
The Mastoid and its Air Cell System: The
mastoid consists of bone cortex with a
"honeycomb“ of air cells underneath.
Depending on development of air cell, three types
of mastoid have been described: Well-pneumatised
or cellular; Diploetic; Sclerotic or acellular
It is divided into:
I. Mesotympanum(lying opposite to parsa
tensa).
II. Epitmpanum or attic( lying above parsa
tensa but medial to shrapnell’s membrane
and the bony lateral attic wall)
III. Hypotympanum( lying below the level of
parca tensa).
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13. BOUNDARIES OF MIDDLE EAR
Roof (Tegmental wall): is formed by a thin plate of bone called tegmen tympani.
Floor (Jugular wall):is also thin plate of bone which separates tympanic cavity from
the jagular bulb
Anterior (Carotid wall):has a thin plate of bone which separates the cavity from
internal carotid artery. has following features: Eustachian tube, Canal of tensor
tympani muscle, Canal for chorda tympani nerve, Attachment of anterior malleolar
ligament
Posterior (Mastoid wall):lies close to the mastoid air cells. Has:
Pyramid, Aditus ad antrum, Facial nerve
Medial (Labyrinthine wall):is formed by labyrinth( including promontory, Round
window, oval window.)
Lateral wall: is formed largely by tympanic membrane.
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14. Auditory ossicles
– Malleus
• Attaches to ear drum
• Articulates with incus
– Incus
• Articulates with stapes
– Stapes (stirrup)
• Footplate of stapes fits into oval
window
Ossicles Allows communication btn
the external and internal ear and
amplification
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15. MIDDLE EAR MUSCLES
There are two middle ear muscles also
called intratympanic muscle : tensor
tympani and the stapedius.
1. Tensor tympani: It runs above the
eustachian tube. Originate from Bony
tunnel above the osseous part of
eustachian tube.inserted Just below the
neck of malleus and is supplied by a
branch of mandibular division of
trigeminal nerve (CN V3)
2. Stapedius: On contraction it reduces
the loud sounds and
prevents noise trauma to the inner ear.
Originate from Conical cavity and canal
within pyramid.it insert to the neck stapes
and supplied by a branch of CN VII
(nerve to stapedius of facial nerve).
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16. Auditory(eustachian)tube
• It consists of both of both bone and hyaline cartilage
and connects the middle ear with the nasopharynx.it is
normally closed at its medial(pharyngeal)end;during
swallowing and yawning,it opens,then atmospheric
pressure from throat enters or leaves the middle ear
until int.pressure is =to external pressure.
• When the pressures are balanced,the eardrum vibrates
freely as soundwaves strike it
• It is also a route where pathogens can travel from throat
and nose to the middle ear
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17. NERVE SUPPLY:
• tympanic plexus which is formed by 1) tympanic branch of
glossopharngeal nerve and 2) sympathetic fibers from the plexus round the
internal carotid artery.
• Tympanic plexus supplies innervation to the medial surface of the
tympanic membrane, tympanic cavity, mastoid air cells and the bony
Eustachian tube. It also carries secretomotor fibres for the parotid gland.
• Chorda Tympani Nerve: It is a branch of the facial nerve which enters
the middle ear through posterior canaliculus, and runs on the medial
surface of the tympanic membrane between the handle of malleus and
long process of incus, above the attachment of tendon of tensor tympani. It
carries taste from anterior two-thirds of tongue and supplies secretomotor
fibres to the submaxi llary and su blingual sa livary glands
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18. Blood supply:
Middle ear is supplied by six arteries, out of which two are the main,
i.e.
(i) Anterior tympanic branch of maxillary artery which supplies
tympanic membrane.
(ii) Stylomastoid branch of posterior auricular artery which supplies
middle ear and mastoid air cells
venous Drainage
Veins from the middle ear cleft drain into pterygoid venous plexus,
superior petrosal sinus and sigmoid sinus
Lymphatic drainage of ear
The lymphatics of middle ear drain into retropharyngeal and parotid
nodes. Eustachian tube lymphatics drain into retropharyngeal group of
lymph nodes . Internal ear does not have any lymphatics
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19. SUMMARY
Middle ear contains:
1. Air
2. Two muscles ( Tensor tympani and stapedius)
3. Two nerves( corda tympani and tympanic plexus on the promontory)
4. 3 bone (maleus, incus, stapes)
Mucosa of middle ear is stratified columnar with goblet and seromucinous glands
Its function:
Conduction
– Conduct sound from the outer ear to the inner ear
Protection
– Creates a barrier that protects the middle and inner areas from foreign objects
– Middle ear muscles may provide protection from loud sounds
Transducer
– Converts acoustic energy to mechanical energy
– Converts mechanical energy to hydraulic energy
Amplifier
– Transformer action of the middle ear
– only about 1/1000 of the acoustic energy in air would be transmitted to the inner-ear
fluids (about 30 dB hearing loss)
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20. INNER EAR
The internal ear or the labyrinth is an important
organ of hearing and balance. It consists of a
bony and a membranous labyrinth.
The membranous labyrinth is filled with a clear
fluid called endolymph while the space between
membranous and bony labyrinths is filled with
perilymph.
Bony labyrinth: It consists of
i. the vestibule,
ii. the semicircular canals and
iii. the cochlea.
Membranous labyrinth: consists of
i. The membranous cochlear duct
ii. The membranous semicircular canals.
iii. The utricle and saccule (that lie within the
vestibule)
iv. The endolymphatic duct and sac
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21. A. Cochlear part
it is fluid filled organ.
it is bony coiled up on axis like
a snail’s shell (central pyramid called
modiolus)
Its basal turn forms the promontory.
It has three compartment
a. Scala vestibule
b. scala tympani
Above 2 are filled with perilymph and
communicate with each other at apex of cochlea through Helicotrema
c. scala media(cochlear duct): its blind coiled tube and it appears triangular on cross-
section and its three wall are formed by:
i. basilar membrane which supports the organ of corti( inner, outer hair cells and
tectorial mem)
ii. The Reissner’s membrane which separate it from scala vestibuli,
iii. The stria vasculars which contains vascular epithelium and is concerned with
secretion of endolymph.
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23. B) Vestibular part:
- its bony cavity that lodges the utricle and saccule.
- it contains the sensory organs responsible for equilibrium ( responsible for linear
acceleration)
C) Semicircular canals(SCC):
they are not complete circles, the have one ampulary and one non-ampulary ends.
Oriented as superior, lateral, posterior canals with 90 degree relation to each other.
Sensory organs are crista ampularis(which is responsible for angular acceleration).
the vestibular nerve:
Superior and inferior vestibular nerve arise from the sensory organs of SCC and utricle and
saccule to enter the internal acoustic canal.
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24. Membranous labyrinth
Cochlear Duct (Membranous Cochlea or Scala Media) This blind coiled tube,
which appears triangular on cross section, is connected to the saccule through
ductus reunions
Saccule: The saccule lies anterior to the utricle opposite the stapes footplate in
the bony vestibule. Its sensory epithelium, macula responds to linear
acceleration and deceleration. The saccule is connected to the cochlea through
the thin reunion duct
Semicircular Ducts: The three semicircular ducts, which open in the utricle,
correspond exactly to the three bony canals
Endolymphatic Duct and Sac: The ducts from utricle and saccule unite and form
utriculo saccular duct, which continues as endolymphatic duct that passes
through thevestibular aqueduct
Endolymphatic sac is thought to regulate pressure of membranous labyrinth.
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25. INNER EAR FLUIDS
Perilymph fills the space between bony and membranous labyrinth while endolymph
fills the entire membranous labyrinth
Perilymph
It resembles extracellular fluid and is rich in sodium ions
Originate from Filtrate of blood serum from the capillaries of spiral ligament and CSF
reaching labyrinth via aqueduct of cochlea.
Endolymph
It resembles intracellular fluid and is rich in potassium ions Protein and glucose
contents are less than in perilymph.
„originate from Stria vascularis and Dark cells of utricle and ampullated ends of
semicircular ducts.
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26. This sensory organ of the hearing, is situated on the basilar membrane. It is spread like a ribbon
along the entire length of basilar membrane. It consists of: 1. Tunnel of Corti: This tunnel, which
is situated between the inner and outer rods, contains a fluid called cortilymph. The functions of
the rods and cortilymph are yet not clear.
2. Hair Cells: hese important receptor cells of hearing transduce sound energy into electrical
energy. There are two types of hair cells—inner and outer.
ORGAN OF CORTI
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27. REFERENCE
1,Harold Ludman and Patrick J Bradley 2007 Ear, Nose and Throat
Fifth Edition
2,Mohan Bansal 2013 Diseases of Ear, Nose and Throat First edition
published by jaypee brothers medical ;New Delhi in India
3, Ghada M W F. Ear Anatomy. Glob J Otolaryngol 2017
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