anatomy of external ear

ANATOMY OF ANATOMY OF EXTERNAL EAREXTERNAL EAR

Presenter :Dr.Razal M Sherif

Moderator :Dr.Joythi swarup

EAREAREXTERNAL EARMIDDLE EARINNER EAR

EXTERNAL EAREXTERNAL EARAURICLE OR PINNAEXTERNAL AUDITORY CANAL

PINNAPINNASingle piece of yellow

elastic cartilage covered with Perichondrium and skin(except lobule and outer part of external auditory canal)

Attached to the side of skull by ligaments and muscles (supplied by facial nerve),muscles are not well developed in human

INCISURA TERMINALIS is a gap between the superior part of tragus and root of helix, which is devoid of cartilage having only fibrous tissue

◦ Endaural approach-inscion made on this area will not cut through the cartilage in surgery of EAC or Mastoid

PINNAPINNA Contd.Contd.

APPLIED ANATOMYAPPLIED ANATOMY

Tragal cartilage, perichondrium from tragus, concha, fat from lobule – reconstruction surgery for middle ear

Conchal cartilage – correct depressed nasal bridge

Composite graft of skin & cartilage from pinna – repair the defects of nasal ala

NERVE SUPPLY - PINNANERVE SUPPLY - PINNA Greater auricular nerve

◦ most of the medial surface of pinna

◦ posterior part of lateral surface

Lesser occipital ◦ upper part of medial

surface Auriculo temporal

◦ tragus◦ crus of helix◦ adjacent part of helix

Auricular branch of vagus◦ concha◦ corresponding eminence on medial surface

Facial nerve◦ distributed with fibers of auricular branch of vagus◦ concha◦ retroauricular groove

NERVE SUPPLY – PINNA Contd

EXTERNAL AUDITORY CANALEXTERNAL AUDITORY CANALExtends from bottom of concha to tympanic

membrane 24 mm (along post wall)not a straight tubeouter part(cartilaginous) directed upwards,

backwards & mediallyinner part (bony) directed downwards,

forwards & mediallypinna pulled upwards, backwards &

laterally(make it straight)

EXTERNAL AUDITORY CANALEXTERNAL AUDITORY CANAL

CARTILAGINOUSBONY

CARTILAGINOUS PARTCARTILAGINOUS PARTOuter 1/3rd & 8mm canalContinuation of cartilage which forms the

frame work of pinna

◦Fissures of Santorini through them parotid or superficial mastoid

infection can appear in the canal or vice versa

Skin covering the cartilaginous canal is thick and contains appendages like 1.CERUMINOUS GLANDS(modified sweat gland),which secrets cerumen (wax) 2.PILOSEBACEOUS GLANDS 3. HAIR is only confined to the outer canal & therefore furuncles are seen only in the outer 1/3rd of canal

BONY PARTBONY PARTInner 2/3rd & 16mmSkin lining the bony canal in thin & continuous

over the tympanic membrane Devoid of skin appendages(Hair and

ceremonious GlandsAbout 6mm lateral to tympanic membrane ,

bony meatus presents as narrowing called ISTHMUS

Foreign body lodged medial to isthmus, get impacted & are difficulty to remove

Anteroinferior part of deep meatus, beyond the isthmus, presents a recess - Anterior recess which acts as a cesspool for discharge & debris

Antero inferior part of bony canal may present a deficiency in children up to age of 4 or sometimes in adults permitting infection to & from parotid (Foramen of Huschke)

NERVE SUPPLY - EACNERVE SUPPLY - EACAuriculo temporal nerve(V3)

◦anterior wall & roofAuricular branch of vagus (X)

◦posterior wall & floorPosterior wall of auditory canal also

receives sensory fibres of CN VII through auricular branch of vagus

TYMPANIC MEMBRANETYMPANIC MEMBRANEForms partition between

EAC & middle earObliquely set – 45deg

with floor of EACPosteriosuperior part

more lateral than Anterioinferior part

9-10 mm tall8-9 mm wide0.1 mm thick

PARS TENSAPARS FLACCIDA (SHRAPNEL’S

MEMBRANE)

TYMPANIC MEMBRANETYMPANIC MEMBRANE

PARS TENSAPARS TENSA

Forms most of Tympanic Membrane Periphery is thickened to form a fibro

cartilaginous ring – ANNULUS TYMPANICUS, which fits in tympanic sulcus

Central part of pars tensa is tented inwards at the level of tip of malleus – UMBO

Bright Cone of Light – seen radiating from the tip of malleus to periphery in anterioinferior quadrant

PARS FLACIDAPARS FLACIDA

Situated above lateral process of malleus between the notch of rivinus & anterior & posterior malleolar fold

Appear slightly Pinkish

LAYERS OF TYMPANIC MEMBRANELAYERS OF TYMPANIC MEMBRANEOuter Epithelial layer

◦ continuous with skin lining the meatusInner mucosal layer

◦ continuous with mucosa of middle earMiddle fibrous layer

◦ encloses the handle of malleus◦ 3 types of fibres

Radial Circular Parobolic

◦ Pars flacida – not organized(Fibrous Layers)

NERVE SUPPLY - TMNERVE SUPPLY - TMAURICULO TEMPORAL NERVE (V3)

◦Anterior half of lateral surfaceAURICULAR BRANCH OF VAGUS (X)

◦Posterior half of lateral surfaceTYMPANIC BRANCH OF CN IX (JACOBSON

NERVE)◦Medial surface

ANATOMY OF EAR Video Presentation