Anatomy of the External Ear
Dr. Supreet Singh Nayyar, AFMCMS (ENT)
External Ear Middle Ear (Cleft) Inner Ear
Parts of the Ear
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
PartsExternal earMiddle earInner ear
ANATOMY OF THE EAR
Pinna
EAC
TM
EXTERNAL EAR
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
Auricle (Pinna)
AURICLE
AURICULAR CARTILAGE
Blood SupplyCranial surface - Posterior auricular ALat surface - Anterior auricular A (Sup temp A)
Nerve supplyGreater auricular (C2-3)Lesser occipital (C2)Auricular branch of Facial (Concha)Auriculotemporal N
Lymphatic drainageMastoid tipPre-auricularDeep cervical
Auricle (Pinna)
PINNA NERVE SUPPLY
PINNA NERVE SUPPLY
From bottom of concha to TM 24 mm along with post wall Lateral cartilaginous and medial bony partCartilage 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 dischargeSkin has no subdermal layer, firmly attached to
periosteum
EXTERNAL AUDITORY CANAL
EAC
Has ceruminous glands in lateral 1/3rdDeficient 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
EXTERNAL AUDITORY CANAL
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 stimulias other apocrine glands. Ad, fever, stress ↑ secretions
CERUMINOUS GLANDS
Ceruminous and sebaceousglands
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
WAX
Tympanic Membrane
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°.
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.
Tympanic Membrane
TYMPANIC MEMBRANE
Landmarks Cone of Light Umbo Handle of Malleus Lat Process of Malleus A & P Malleolar Fold +/- Incus shadow Annulus
TYMPANIC MEMBRANE ON OTOSCOPY
Tympanic Membrane - Quadrants
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 otalgia5. Imp donor of cartilage and fat 6. Isthmus holds the FB7. Vagus stimulation to increase appetite
APPLIED ANATOMY
8. Sagging of deep postero superior wall – Ac mastoiditis
9. Furuncles only in lat part, very painful10. Persistent cough by impacted wax11. Cymba conchae direct relation to
suprameatal triangle12. Skin has unique quality of migrating
laterally
APPLIED ANATOMY
Thank You
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