3. Hearing is a primitive sense and is essential in all
animals
Well developed and well protected
It needs a sound source, conducting mechanism,
end organ and a central processor
Parts Pinna
External ear EAC
Middle ear TM
Inner ear
4.
5. Projects from the side of the head (shape size and
angle varies)
Shape maintained by a yellow elastic cartilage (one
piece of cartilage forming pinna and external part
of EAC, except lobule)
Covered with skin
Several elevations and depressions
6.
7.
8. Blood Supply
Cranial surface - Posterior auricular A
Lat surface - Anterior auricular A (Sup temp A)
Nerve supply
Greater auricular (C2-3)
Lesser occipital (C2)
Auricular branch of Facial (Concha)
Auriculotemporal N
Lymphatic drainage
Mastoid tip
Pre-auricular
Deep cervical
9.
10.
11. From bottom of concha to TM
24 mm along with post wall
Lateral cartilaginous and medial bony part
Cartilage part
Outer 1/3 (8 mm), deficient at Incisura terminalis (root of
helix and tragus)
Skin is thick with hairs and sebaceous and ceruminous
glands (Apo-pilo-sebaceous Units)
Fissures in ant wall ‘fissures of Santorini’
Bony Part
Medial 2/3 (16 mm)
Two constrictions (Isthmus 5 mm lateral to TM)
Ant recess sump for discharge
Skin has no subdermal layer, firmly attached to
periosteum
12.
13. Has ceruminous glands in lateral 1/3rd
Deficient in children
Blood Supply
Ext Carotid system (Sup temporal, Maxillary, Post
auricular)
Nerve supply
Ant half Auriculotemporal N, post half by Arnold’s N
(X)
Relations
Ant - TMJ
Post - Mastoid
Sup - Middle fossa
Inf - Parotid gland
14. Simple, tubular, coiled structure having
myoepithelium
Secretions expressed into root canal
Watery white secretion initially dries up and gets
oxidised and becomes sticky and dark in colour
Modified sweat glands and react to same stimuli
as other apocrine glands. Ad, fever, stress ↑
secretions
15.
16. Mixture of secretions of ceruminous and sebaceous
glands
Two types dry and wet
Dry wax – yellowish or grey, dry and white
Wet wax – yellowish brown, wet and sticky
Contains amino acids, fatty acids, lysozymes and
immunoglobulins.
Has a bactericidal activity
Migrates outside but may get impacted
17. The external ear canal
describes an S - like
pathway from the
entrance to the TM.
The TM separates the
external ear canal from
the middle-ear cavity and
is inserted at an angle of
approximately 55°.
18. Separates auditory meatus of external
ear from tympanic cavity of middle ear.
Composed of four strata arranged in 3
general layers
◦ Outermost (cutaneous - ectoderm) very thin
skin
◦ Middle (connective tissue - mesoderm)
Radiate (radiatum) fibroelastic connective tissue
Circular (circulare) fibroelastic connective tissue
In the Pars flaccida the radiate and circular layers are
extremely thin and considered absent
Annulus fibrosus
◦ Innermost (mucosa - endoderm) mucous
membrane, with low cuboidal epithelium
continuous with lining of tympanic cavity.
19. Landmarks
Cone of Light
Umbo
Handle of Malleus
Lat Process of Malleus
A & P Malleolar Fold
+/- Incus shadow
Annulus
23. 1. Lat part of EAC runs inwards, downwards and
forwards. Ear pulled out, post and laterally
2. Relatively less subcutaneous tissue makes the
pinna more sensitive to frost bite
3. Incisura terminalis is used for end-aural incision
4. Referred otalgia
5. Imp donor of cartilage and fat
6. Isthmus holds the FB
7. Vagus stimulation to increase appetite
24. 8. Sagging of deep postero superior wall – Ac
mastoiditis
9. Furuncles only in lat part, very painful
10. Persistent cough by impacted wax
11. Cymba conchae direct relation to suprameatal
triangle
12. Skin has unique quality of migrating laterally