This is just a review of anatomy before discussing about external ear in clinical .

1. ANATOMY OF EXTERNAL EAR --- ENT
6TH SEMESTER MBBS
NISCHAL SHRESTHA

2. CONSISTS OF
i) AURICLE OR PINNA
ii) EXTERNAL ACOUSTIC CANAL
iii) TYMPANIC MEMBRANE

3. AURICLE OR PINNA
• EXCEPT LOBULE AND OUTER PART OF EXTERNAL ACOUSTIC CANAL, ENTIRE
PINNA IS MADE UP OF SINGLE PIECE OF YELLOW ELASTIC CARTILAGE
COVERED WITH SKIN
• LARGE DEPRESSION CALLED CONCHA LEADS INTO EXTERNAL ACOUSTIC
MEATUS
• THERE ARE A NO OF MUSCLES AND THESE ARE VESTIGIAL IN MAN. IN
LOWER ANIMALS, INTRINSIC MUSCLES ALTER SHAPE WHILE, EXTRINSIC
MOVE THE AURICLE AS A WHOLE

4. • THERE IS NO CARTILAGE BETWEEN TRAGUS AND CRUS OF HELIX & THIS
AREA IS CALLED INCISURA TERMINALIS
• AN INCISION MADE IN THIS AREA WILL NOT CUT THROUGH CARTILAGE
AND IS USED FOR ENDAURAL APPROACH IN SURGERY OF EXTERNAL
AUDITORY CANAL OR MASTOID

5. • CARTILAGE FROM TRAGUS , PERICHONDRIUM FROM TRAGUS OR CONCHA
AND FAT FROM LOBULE ARE FREQUENTLY USED FOR RECONSTRUCTIVE
SURGERY OF MIDDLE EAR.
• THE CONCHAL CARTILAGE HAS ALSO BEEN USED TO CORRECT THE
DEPRESSED NASAL BRIDGE WHILE THE COMPOSITE GRAFT OF SKIN AND
CARTILAGE FROM PINNA ARE USED FOR REPAIR OF DEFECTS OF NASAL
ALA

7. NERVE SUPPLY
1. GREATER AURICULAR NERVE (C2,3) SUPPLIES MOST OF THE MEDIAL
SURFACE OF PINNA AND ONLY POSTERIOR PART OF LATERAL SURFACE
2. LESSER OCCIPITAL (C2) SUPPLIES UPPER PART OF MEDIAL SURFACE
3. AURICULOTEMPORAL (V3) SUPPLIES TRAGUS , CRUS OF HELIX AND
ADJACENT PART OF HELIX
4. AURICULAR BRANCH OF VAGUS (CN X), ALSO CALLED ARNOLD’S NERVE,
SUPPLIES CONCHA AND CORRESPONDING EMINENCE ON MEDIAL SURFACE
5. FACIAL NERVE , WHICH IS DISTRIBUTED WITH FIBRES OF AURICULAR
BRANCH OF VAGUS, SUPPLIES CONCHA AND RETROAURICULAR GROOVE

9. BLOOD SUPPLY & LYMPHATICS
• POSTERIOR AURICULAR ARTERY
• SUPERFICIAL TEMPORAL ARTERY
• LYMPHATICS DRAIN INTO PREAURICULAR AND POSTAURICULAR LYMPH
NODES

10. EXTERNAL ACOUSTIC/ AUDITORY CANAL
(EAC)
• EXTENDS FROM BOTTOM OF CONCHA TO TYMPANIC MEMBRANE
• 24MM ALONG POSTERIOR WALL
• NOT A STRAIGHT TUBE, RATHER S SHAPED
• OUTER/ MIDDLE PART IS DIRECTED UPWARDS, BACKWARDS & MEDIALLY
• INNER PART IS DIRECTED DOWNWARDS , FORWARDS AND MEDIALLY
• SO, TO SEE TYMPANIC MEMBRANE, PINNA HAS TO BE PULLED UPWARDS,
BACKWARDS, AND LATERALLY SO AS TO BRING TWO PARTS IN ALIGNMENT

11. • CANAL IS DIVIDED INTO 2 PARTS :
i) CARTILAGINOUS PART OUTER 1/3RD (8MM)
ii) BONY PART  INNER 2/3RD (16MM)
BONY PART IS NARROWER THAN CARTILAGINOUS PART

12. CARTILAGINOUS PART
• IS CONTINUATION OF CARTILAGE WHICH FORMS PINNA
• IT HAS TWO DEFICIENCIES– THE “FISSURES OF
SANTORINI” IN THIS PART OF CARTILAGE
• THROUGH THEM THE PAROTID OR SUPERFICIAL MASTOID INFECTIONS CAN
APPEAR IN THE CANAL OR VICE VERSA

15. • THE SKIN COVERING THE CARTILAGINOUS CANAL IS THICK AND CONTAINS
CERUMINOUS AND PILOSEBACEOUS GLANDS WHICH SECRETE WAX
• HAIR IS ONLY CONFINED TO OUTER CANAL AND THEREFORE FURUNCLES
(STAHPH INFECTION OF HAIR FOLLICLES) ARE SEEN ONLY IN OUTER 1/3RD
OF CANAL

16. BONY PART
• SKIN LINING BONY CANAL IS THIN AND CONTINUOUS OVER TYMPANIC
MEMBRANE
• DEVOID OF HAIR, AND CERUMINOUS GLANDS
• ABOUT 6MM LATERAL TO TYMPANIC MEMBRANE, BONY MEATUS(CANAL)
PRESENTS A NARROWING CALLED ISTHMUS
• FOREIGN BODIES,LODGED MEDIAL TO ISTHMUS, GETS IMPACTED AND ARE
DIFFICULT TO REMOVE

19. • ANTEROINFERIOR PART OF DEEP MEATUS BEYOND THE ISTHMUS,
PRESENTS A RECESS CALLED ANTERIOR RECESS
• THIS ACTS AS A CESSPOOL FOR DISCHARGE AND DEBRIS IN EXTERNAL AND
MIDDLE EAR INFECTIONS
• [CESSPOOL= UNDERGROUND CONTAINER FOR TEMPORARY STORAGE OF
LIQUID WASTES AND SEWAGE]

20. • ANTEROINFERIOR PART OF BONY CANAL MAY PRESENT A DEFICIENCY
(FORAMEN OF HUSCHKE) IN CHIDREN UPTO AGE OF 4 OR SOMETIMES
EVEN IN ADULTS , PERMITTING INFECTIONS TO AND FROM PAROTID
• THE FORAMEN TYMPANICUM (ALSO KNOWN AS FORAMEN OF HUSCHKE) IS AN
ANATOMICAL VARIATION IN THE EXTERNAL ACOUSTIC CANAL (EAC), WHERE A
BONY DEFECT CONNECTS THE EAC TO THE TEMPOROMANDIBULAR JOINT (TMJ).

22. NERVE SUPPLY OF EAC
1. ANTERIOR WALL & ROOF: AURICULOTEMPORAL (V3)BRANCH OF
MANDIBULAR NERVE
2. POSTERIOR WALL & FLOOR: AURICULAR BRANCH OF VAGUS (CN X)
3. POSTERIOR WALL ALSO RECEIVES SENSORY FIBRES OF CN VII THROUGH
AURICULAR BRANCH OF VAGUS
AND FACIAL NERVE INJURY LEADS TO HYPOAESTHESIA OF POSTERIOR
MEATAL WALL K/A HITZELBERGER’S SIGN
 IN HERPES ZOSTER OTICUS, LESIONS ARE SEEN IN DISTRIBUTION OF
FACIAL NERVE , I.E. CONCHA, POSTERIOR PART OF TYMPANIC MEMBRANE
AND POSTAURICULAR REGION

24. TYMPANIC MEMBRANE OR THE DRUMHEAD
• IS A SEMI-TRANSPARENT PARTITION BETWEEN EAC AND MIDDLE EAR
• IS OBLIQUELY SET AT 55° WITH FLOOR OF MEATUS AND SO, ITS
POSTEROSUPERIOR PART IS MORE LATERAL THAN ITS ANTEROINFERIOR
PART
• 9-10 MM TALL,
• 8-9 MMM WIDE
• 0.1 MM THICK

25. • MEMBRANE HAS OUTER AND INNER SURFACES
• OUTER SURFACE IS LINED BY THIN SKIN AND IS CONCAVE
• INNER SURFACE PROVIDES ATTACHMENT TO HANDLE OF MALLEUS WHICH
EXTENDS UPTO ITS CENTRE
• INNER SURFACE IS CONVEX.
• THE POINT OF MAXIMUM CONVEXITY LIES AT TIP OF HANDLE OF MALLEUS
AND IS CALLED UMBO
• THIS MEMBRANE IS HELD TENSE BY INWARD PULL OF TENSOR TYMPANI
MUSCLE WHICHI IS INSERTED INTO UPPER END OF HANDLE OF MALLEUS
• TYMPANIC MEMBRANE CAN BE DIVIEDED INTO TWO PARTS

26. 1. PARS TENSA
• GREATER PART OF T. MEMBRANE IS TIGHTLY STRETCHED AND IS
THEREFORE, CALLED PARS TENSA
• ITS PERIPHERY IS THICKENED TO FORM A CARTILAGINOUS RING CALLED
ANNULUS TYMPANICUS, WHICH FITS IN TYMPANIC SULCUS OF TEMPORAL
BONE
• THE CENTRAL PART IS TENTED INWARDS AT LEVEL OF TIP OF MALLEUS
AND IS CALLED UMBO
• A BRIGHT CONE OF LIGHT CAN BE SEEN RADIATING FROM TIP OF MALLEUS
TO PERIPHERY IN ANTEROINFERIOR QUADRANT

27. • THIS CORRESPONDS TO THE 4 O'CLOCK TO 5 O'CLOCK POSITION IN THE
RIGHT EARDRUM AND THE 7 O'CLOCK TO 8 O'CLOCK POSITION IN THE LEFT
EARDRUM

28. 2. PARS FLACCIDA (SHARPNELL’S
MEMBRANE)
• IS SITUATED ABOVE LATERAL PROCESS OF MALLEUS BETWEEN NOTCH OF
RIVINUS AND ANTERIOR AND POSTERIOR MALLEAL FOLDS (EARLIER
CALLED MALLEOLAR FOLDS)
• IT IS LOOSE AND MAY APPEAR SLIGHTLY PINKISH
• IT IS CROSSED INTERNALLY BY CHORDA TYMPANI
• THIS PART IS MORE LIABLE TO RUPTURE THAN PARS TENSA

29. LAYERS OT TYMPANIC MEMBRANE
• CONSISTS OF 3 LAYERS
1. OUTER EPITHELIAL LAYER, WHICH IS CONTINUOUS WITH SKIN LINING OF
MEATUS
2. MIDDLE FIBROUS LAYER, WHICH ENCLOSES HANDLE OF MALLEUS AND
HAS 3 TYPES OF FIBRES- RADIAL(SUPERFICIAL), CIRCULAR(DEEP) AND
PARABOLIC. THE CIRCULAR FIBRES ARE MINIMUM AT CENTRE AND MAX
AT PERIPHERY.
> FIBROUS LAYER IN PARS FLACCIDA IS THIN AND NOT ORGANIZED INTO
VARIOUS FIBRES AS IN PARS TENSA.
3. INNER MUCOSAL LAYER, WHICH IS CONTINUOUS WITH MUCOSA OF INNER
LAYER

31. NERVE SUPPLY
1. ANTERIOR HALF OF LATERAL SURFACE : AURICULOTEMPORAL
2. POSTERIOR HALF OF LATERAL SURFACE : AURICULAR BRANCH OF VAGUS
3. MEDIAL SURFACE : TYMPANIC BRANCH OF CN IX (JACOBSON’S
NERVE)