ANATOMY OF EXT EAR AND RELATED STRUCTURES

ANATOMY OF EXT EAR AND RELATED STRUCTURES

1. ANATOMY OF EXTERNAL EAR DR PNKY SHAH DEPARTMENT OF E.N.T

2. EAR EXTERNAL EAR MIDDLE EAR INNER EAR

3. EXTERNAL EAR AURICLE OR PINNA EXTERNAL AUDITORY CANAL

4. PINNA Single 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

5. 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 PINN A C o nt d .

6. APPLIED 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

7. NE R V E S U P PL Y - P INNA 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

8. 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

9. EX T E R N A L A U D I T O R Y CAN AL Extends from bottom of concha to tympanic membrane 24 mm (along post wall) not a straight tube outer part(cartilaginous) directed upwards, backwards & medially inner part (bony) directed downwards, forwards & medially pinna pulled upwards, backwards & laterally(make it straight)

10. EX T E R N A L A U D I T O R Y CAN AL CARTILAGINOUS BONY

11. C A R TIL A GI N O U S PA R T Outer 1/3 rd & 8mm canal Continuation of cartilage which forms the frame work of pinna Fissures of Santorini  t h r o ug h th em pa r o t i d o r s up e r f i c ia l m a s t o id infection can appear in the canal or vice versa

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

13. BON Y P A RT Inner 2/3 rd & 16mm Skin lining the bony canal in thin & continuous over the tympanic membrane Devoid of skin appendages(Hair and ceremonious Glands About 6mm lateral to tympanic membrane , bony meatus presents as narrowing called ISTHMUS Foreign body lodged medial to isthmus, get impacted & are difficulty to remove

14. 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 )

15. NE R V E S U P PL Y - EAC Auriculo temporal nerve(V3) anterior wall & roof Auricular branch of vagus (X) posterior wall & floor Posterior wall of auditory canal also receives sensory fibres of CN VII through auricular branch of vagus

16. TYMPANIC MEMBRANE Forms partition between EAC & middle ear Obliquely set – 45 deg with floor of EAC P o s t e r i o s up e r i o r p a r t more lateral than Anterioinferior part 9-10 mm tall 8-9 mm wide 0.1 mm thick

17. PARS TENSA PARS FLACCIDA (SHRAPNEL ’ S MEMBRANE) TYMPANIC MEMBRANE

18. PARS 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

19. PARS FLACIDA Situated above lateral process of malleus between the notch of rivinus & anterior & posterior malleolar fold Appear slightly Pinkish

20. LAYERS OF TYMPANIC MEMBRANE Outer Epithelial layer continuous with skin lining the meatus Inner mucosal layer continuous with mucosa of middle ear Middle fibrous layer encloses the handle of malleus 3 types of fibres  Radial  Circular  Parobolic Pars flacida – not organized(Fibrous Layers)

21. NE R V E S U P PL Y - TM AURICULO TEMPORAL NERVE (V3) Anterior half of lateral surface AURICULAR BRANCH OF VAGUS (X) Posterior half of lateral surface TYMPANIC BRANCH OF CN IX (JACOBSON NERVE) Medial surface