anatomy of the external ear dr. supreet singh nayyar, afmc ms (ent) for more presentations, visit
TRANSCRIPT
Anatomy of the External Ear
Dr. Supreet Singh Nayyar, AFMCMS (ENT)
For more presentations, visit www.nayyarENT.com
Parts of the Ear• External Ear• Middle Ear (Cleft)• Inner Ear
ANATOMY 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
Parts External ear Middle ear Inner ear
Pinna
EAC
TM
EXTERNAL EAR
Auricle (Pinna)• 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
AURICULAR CARTILAGE
Auricle (Pinna)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 drainageMastoid tipPre-auricularDeep cervical
PINNA NERVE SUPPLY
PINNA NERVE SUPPLY
EXTERNAL AUDITORY CANAL
• 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
EAC
EXTERNAL AUDITORY CANAL
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
CERUMINOUS GLANDS• 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 and sebaceousglands
WAX• 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
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°.
Tympanic Membrane
• Separates auditory meatus of external ear from tympanic cavity of middle ear.
• Composed of four strata arranged in 3 general layers o Outermost (cutaneous - ectoderm) very thin
skin o 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
o Innermost (mucosa - endoderm) mucous membrane, with low cuboidal epithelium continuous with lining of tympanic cavity.
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
APPLIED ANATOMY1. 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 ANATOMY8. Sagging of deep postero superior wall – Ac
mastoiditis9. 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