2. PARTS OF EXTERNAL EAR
• Auricle or pinna
• External acoustic canal
• Tympanic membrane
3. AURICLE/PINNA
• The auricle except it’s lobule is made up of single piece of yellow
elastic cartilage, which is covered with skin
• The skin is adherent to perichondrium on it’s lateral surface while
it is slightly loose on the medial surface
• Lobule is made of fibrofatty tissue.
• Various elevation and depression can be seen in lateral surface of
pinna.
5. GAPS
• INCISURA TERMINALIS-gap between tragus and helix
• INTERTRAGIC NOTCH-gap between tragus and antitragus
• Incisura terminalis is devoid of cartilage.
• ENDAURAL INCISION-Made in incisura terminalis for surgery of EAC
and middle ear.
6. USES IN GRAFTING
• Grafts in rhinoplasty- conchal cartilage is frequently used to
correct depressed nasal bridge
• Grafts in tympanoplasty- tragal and conchal cartilage and
perichondrium and fat from lobules is used during tympanoplasty
operation
7. NERVESUPPLYOFPINNA
• Great auricular nerve(C2,C3)-supplies most of medial surface and posterior part
of lateral surface.
• Lesser occipital(C2)-supplies upper part of medial surface.
• Auriculotemporal(V3)-supplies tragus,crus of helix and adjacent part of helix.
• Auricular branch of vagus(CN X)-also called as Arnold’s nerve,supplies concha
and eminence on the medial surface
• Facial nerve which is distributed with fibres of auricular branch of vagus,supplies
the concha and retroauricular groove
9. EXTERNAL AUDITORY (ACOUSTIC)
CANAL
• Extends from bottom of concha to the tympanic
membran
• It measures about 24 mm along it’s posterior wall
• It is not a straight tube,it’s outer part directed-
upwards, backwards and medially while inner part
directed downwards,forwards and medially (S-
shaped curve)
• EAC divided into cartilaginous and bony parts.
10. CARTILAGINOUS PART
• It is the continuation of cartilage that forms the framework of pinna
• Forms outer one-third of the canal(8mm)
• Fissures of santorini-these lie in the anterior wall , are a pathway through
which parotid abscess may drain via EAC and vice versa.
• Skin covering the cartilaginous part is thick and contains ceruminous and
pilosebaceous gland which secrete wax.
• Hair follicles are confined only to outer cartilaginous canal ,so
furuncles(Staphylococcal infection ) are seen only here.
11. BONYPART
• Forms inner two-third of the canal(16 mm)
• Skin lining bony canal is thin and continuous over tympanic
membrane.
• It is devoid of hair and ceruminous glands.
• Approximately 6mm lateral to tympanic membrane,bony EAC has a
narrowing called isthmus.
• Foreign bodies impacted medial to bony isthmus of EAC are
difficult to remove
12. RECESSANDFORAMENOFHUSCHKE
Anterior recess: °present in the anteroinferior part
of bony canal,medial to isthmus
°it acts as a cesspool for discharge
and debris.
Foramen of huschke:°In children and occasionally
in adults, anteroinferior bony canal may have
deficiency that is called foramen of huschke.
°It permits spread of EAC
infection to and from parotid and TMJ
13. RELATIONS OF EXTERNAL AUDITORY MEATUS
• Superiorly : Middle cranial fossa
• Posteriorly : mastoid air cells and facial nerve
• Inferiorly : parotid gland
• Anteriorly : Temporomandibular joint
• Acute mastoiditis causes sagging of posterosuperior part of deeper bony EAC because it is related with
mastoid antrum.
14. NERVE SUPPLY OF EXTERNAL AUDITORY
CANAL
• Auriculotemporal (V3) : anterior wall and roof
• Auricular branch of vagus(CN X) : posterior wall and floor
• Facial nerve : skin of mastoid and posterior EAC
15. TYMPANIC MEMBRANE
• Thin, semi-transparent,pearly white in colour and it
forms the partition between EAC and middle ear.
• It is obliquely set and forms an angle of 55° with deep
EAC.
• It is 9-10mm tall
8-9mm wide
0.1mm thick
16. STRUCTURE
Tympanic membrane consist of the following
three layer
• Outer epithelial layer- continuous with the
skin lining EAC
• Middle fibrous layer- encloses the handle of
malleus and consist of three type of
fibres:radial, circular and parabolic.
• Inner mucosal layer- continuous with middle
ear mucosa.
17. PARS TENSA
• Forms most of the tympanic membrane
• It’s periphery is thickened to form a fibrocartilaginous ring called
annulus tympanicus.
• Central part of pars tensa is tented inward at the level of tip of
malleus called umbo.
• When TM is illuminated,a bright cone of light is seen radiating
from tip of malleus to the periphery of antero inferior quadrant.
18. PARS FLACCIDA(SHARPNELL’S
MEMBRANE)
• Situated above the lateral process of malleus between the
notch of rivinus and anterior and posterior malleal fold.
• It is not so tense as pars tensa and may appear slightly
pinkish.
• In pars flaccida,the middle fibrous layer is very thin and
not organized into various fibres.
19. APPLIED ANATOMY
• Perforation of the tympanic membrane:It may
result from an external injury or middle ear
infection (otitis media).It may lead to middle ear
deafness.
• Bullous myringitis:it is an infection involving the
tympanic membrane.Examination of the ear may
reveal tympanic membrane to have clear or
reddish blister on it .
20. NERVE SUPPLY OF TYMPANIC
MEMBRANE
• Auriculotemporal nerve – anterior half of lateral
surface of TM
• Vagus nerve(auricular branch)- posterior half of
lateral surface
• Glossopharyngeal nerve(tympanic branch)-
medial surface of TM
21. BLOOD SUPPLY OF EXTERNAL EAR
• The major supply to the external ear is
the posterior auricular branch of
the external carotid artery.
• The anterior auricular branch of the
superficial temporal artery also brings
blood to the anterior aspect of the
external ear.
• The posterior auricular artery supplies
the external acoustic meatus along with
the auricular branches of the
maxillary and superficial temporal
arteries.
22. DEVELOPMENT OF MIDDLE EAR
• Pinna is derived from mesenchymal tissue of the 1st and 2nd pharyngeal arches.
• 1st pharyngeal arch- tragus
• 2nd pharyngeal arch- crus of helix,helix,anti helix,anti tragus,ear lobule
• External auditory meatus is derived from the dorsal portion of 1st pharyngeal cleft.
• Tympanic membrane develops from first pharyngeal membrane.
cuticular layer- derived from ectoderm
intermediate layer- derived from mesoderm
mucous layer- derived from endoderm
23. SOURCE
• Diseases of ear, nose and throat - P.L.Dhingra
• Diseases of ear, nose and throat – Mohan Bansal
• Ear, nose and throat simplified – Bachi T Hathiram | Vicky S Khattar
