Anatomy of the external ear

An overview of the Anatomy of the External Ear for medical students, undergraduates or postgraduates as well.

1. Prof. Dr. Ausaf Ahmed Khan
MBBS. DLO. FCPS. FRCS(Glasg)
Member IWGEES (International Working
Group of Endoscopic Ear Surgery)
Head of ENT / Head and Neck Surgery
Hamdard College of Medicine & Dentistry
Hamdard University. Karachi, Pakistan
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Anatomyofthe
ExternalEar

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EXTERNAL EAR
P
i
n
n
a

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The Pinna or auricle, is a flattened, funnel-
shaped appendage composed of cartilage
and covered by skin.
Has rudimentary functions in humans in terms
of sound localization and amplification.
The folds or convolutions of the auricle may,
to some extent, shield the external auditory
canal from foreign objects or insects.
AURICLE/ PINNA

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The pinna
Development
Six hillocks develop around the 1
st
pharyngeal groove.
Three hillocks develop on each side of the groove.
Bulk of auricle develop from mesenchyme of hyoid arch.
Rudimentary pinna has formed around 60 days

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The auricle develops from six hillocks
situated around the dorsal extremity of the
first branchial groove. Between four and six
weeks of gestation, three anterior hillocks
arise from the first (mandibular) arch, and
three posterior hillocks develop on the
second (hyoid) arch. By the end of the six
weeks, these hillocks are transformed into
the folds of the developing auricle.

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Stages
in the
development
of PINNA

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Normal infant pinna
Normal adult pinna
Ageingpinna

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The Pinna
Introduction
projects from the side of head & has some
function in collecting sounds
lateral surface has several prominences
and depressions
medial surface has corresponding elevations
thin elastic cartilage continuous with cartilage
of External Auditory Canal
connected to the surrounding parts by
ligaments and muscles

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The Pinna
lateral surface

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Elongated
lobule
Creased lobule
Attached earlobe
Darwin’s
tubercle
Reverse
Darwin’s tubercle
MINOR ANATOMIC VARIATIONS

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The Pinna
Skin
Skin is thin
On lateral surface; closely adherent to
perichondrium
this makes it susceptible to frostbite
On medial surface; there is a definite layer
of sub dermal adipose tissues
Covered by fine hairswith sebaceous glands

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Hairy Tragus
Hairy Pinna
Hypertrichosis

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Single piece of elastic fibro-cartilage
Absent in lobule
Deficient b/w crus of helix and tragus
Nutrition depends on perichondrium
Connected to temporal bone by
–Extrinsic ligaments;
Anterior / Posterior ligaments
–Intrinsic ligaments;
connects various parts of the cartilaginous
auricle
The Pinna
Cartilaginous skeleton

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The Pinna
Muscles
There are Extrinsic and Intrinsic muscles ;
Extrinsic muscles
1.auricularis anterior
2.auricularis posterior
3.auricularis superior
Intrinsic muscles
–six , small, inconsistent
–No useful function
(other than entertainment)

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The Pinna
Blood supply
Three branches from external carotid artery
supply the external ear;
1.Posterior Auricular A.
2.Anterior Auricular A.
3.Superficial temporal A.

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The Pinna
Nerve supply
Great Auricular nerve,C2
Lesser Occipital nerve,C2,3
Auriculotemporal nerve, Vc
Facial nerve,VIICN
Auricular (Arnold’s)
branch of Vagus, X

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•Great Auricular n., C2
•Lesser Occipital n.,C2,3
•Auriculotemporal n., Vc
•Facial nerve, VII CN
•Auricular (Arnold’s)
branch of Vagus, X
Nerve
supply
Referred otalgia…

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The Pinna
Lymphatic Drainage
1.From posterior surface
nodes at mastoid tip
2.From tragus and upper
part of anterior surface
pre-auricular nodes
3.From rest of auricle
upper deep cervical
nodes
1
2
3

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External Auditory Canal
Introduction
Extendsfrom Concha to the tympanic membrane
Total lengthis 2.5cms
Frameworkis
–cartilaginous in outer 1/3rd
–bony in medial 2/3rd
In adults cartilage part runs inward slightly upwards
and backwards. Bony part runs inward slightly
downwards and forwards
In Neonates; virtually no bony meatus

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EAC
Introduction
Size and shape of canal varies
Two prominences limits the visibility of TM;
1.Floorhas upward convexity at its
midpoint
2.Anteriorwallhas posterior bulge at its
midpoint

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EAC
Development
b1-developing meatus
b2-string of epithelium
b4,c4-primitive ME cavity
b9,d9-tympanic plate
b8,d8-sq. part of temp bone
d5-epitmpanum
d6-mesotympnaum
a b
c d
Develops as a thickening of the ectoderm
at the upper end of 1
st
pharyngeal cleft

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EAC
Cartilaginous part
about 8mm long
continuous with auricular cartilage
deficient superiorly
medial border is attached to the rim of the
bony canal
skin is relatively thick & has numerous fine
hairs with excessive sebaceous glands

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EAC
Bony part
is 1.8 cms long.
ant. wall is longer
narrower than cartilaginous part
Formedbytympanic and
squamous temporal bone.
medial end has tympanic sulcus.
has 2 constrictions;
–bony / cartilage junction
–Isthmus5mm from TM
deep to isthmus there is an
anteriorrecessb/w TM & EAC

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EAC
Skin
is continuous with that of pinna
extendsover the outer surface of tympanic
membrane
in cartilaginous part, has a definite sub-dermal layer
in bony part, is very thin and adherent to the
periosteum
in superior portion of the deep meatus, between
two suture lines, sub-dermal layer is thickened and
carries a leash of blood vessels , called the
vascularstrip

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EAC
Skin
Has some peculiar characteristics;
cell maturation of epidermal cells occurs laterally
layers of keratin are shed towards the surface
opening of EAM (determined by the radial fibers
arrangement on TM)
the same occurs in tympanic membrane
rate of migration = 0.05 mm/day
integrity of skin depends on surface ventilation…

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EAC
Skin appendages
Sebaceous glands
typical gland, alveolus,
duct
Alveolus has epithelial
cells & basement
membrane
Central cells form sebum
Sebum opens along hair
follicles
Ceruminous glands
are modified apocrine
sweat glands
lies deeper in dermis
secretion contributes
in wax formation
•Cartilaginous part’s skin has hairs and glands
•Glands are of 2 types

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Blood supply,
Venous & Lymphatic drainage
Blood supply
Auricular branches of
superficial temporal artery
roof and anterior portion
of canal.
Deep auricular branch of
maxillary artery (1st part)
anterior meatal wall skin
and outer surface of TM.
Auricular branches of
posterior auricular artery
posterior portion of EAC.
Venous
Drainage
External jugular vein
Maxillary veins
Pterygoid plexus
Lymphatic
Drainage
Same as for Pinna

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Blood supply

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EAC
Nerve supply
IXCN
VCN
XCN

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EAC
Relationships
Superior
–middle cranial fossa
Anterior
–T.M. joint
–parotid gland
–Superf. temporal A./V.
–auriculotemporal nerve
Posterior
–mastoid
Inferior
–jugular bulb & ICA
–facial nerve
–styloid process
–parotid gland
–digastric muscle
Medial
–mastoid
Lateral
–outside world

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Thank you