External ear anatomy

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