ANATOMY OF EXTERNAL EAR

external ear anatomy

1. mmm DR MOHAMMED NISHAD N

2. C ONTENTS EMBRYOLOGY ANOMALIES STRUCTURE BLOOD SUPPLY NERVE SUPPLY LYMPHATIC DRAINAGE CLINICAL & SURGICAL IMPORTANCE

3. EMBRYOLOGY EXTERNAL EAR Develops from first branchial cleft

4. PINNA Around 6 th week of IUL Develops from six hillocks or TUBERCLES OF HIS around 1 st pharyngeal cleft . 1 ST Tubercle- 1 st branchial arch REST – 2 nd branchial arch

5. STRUCTURES DERIVED Tragus Crus of helix Helix Antihelix Scapha & antitragus Ear lobule

6. ANOMALIES OF PINNA

7. PRE-AURICULAR SINUS - Defective fusion of tubercles . ANOTIA – Failure of development of hillocks . BAT EAR DEFORMITY – Defective development of 4 th tubercle causing absence of antihelix . CRYPTOTIA (hidden or pocket ear) - an abnormality of the auricle where the upper pole is buried beneath the temporal skin . MICROTIA (diminutive ear) - is usually an isolated congenital abnormality, but is sometimes associated with recognized syndromes, e.g. fetal alcohol syndrome, maternal diabetic syndrome, thalidomide and isotretinoin exposure.

8. POLYOTIA (mirror ear) - is caused by persistence of pre- auricular tissue that would normally be included in the pinna, but instead lies in front of the tragus in the posterior aspect of the cheek . STAHL’S E AR - helix is flattened and the upper crus of the antihelix is duplicated, producing a ridge of cartilage running from the antihelix to the rim of the helix. This causes a pointing of the ear and a reversal of the normal concavity of the scaphoid fossa. Occasionally, the upper part of the pinna flops over to produce an appearance known as ‘ lop ear

9. CRYPTOTIA MICROTIA STAHL’S BAR POLYOTIA LOP EAR

10. EXTERNAL AUDITORY CANAL Develops around the 1 st branchial cleft as an invagination into funnel shaped pit to form primary EAC. Subsequent medial growth with solid core of ectoderm leads to formation of a meatal plate called secondary EAC. Between 8 th -10 th week of IUL solid core of epithelium undergoes canalization form in definitive EAC .

11. ANOMALIES OF EAC

12. TYMPANIC MEMBRANE

13. ANATOMY – EXTERNAL EAR AURICLE / PINNA EAC TYMPANIC MEMBRANE

14. PINNA Single sheet of yellow elastic fibrocartilage 2 surfaces- medial(cranial) , lateral. Medial surface- convex Lateral surface- concave with folds & hollows. AURICULAR CARTILAGE

15. Lateral surface HELIX – most prominent outer fold. ANTIHELIX - fold infront of helix. CONCHA – infront of antihelix , hollow space divided by crus of helix – Cymba conchae & Cavum conchae. TRAGUS - cartilaginous projection anterior to cavum concha. SCAPHOID FOSSA – boat shaped space b/w upper part of helix & antihelix . INCISURA TERMINALIS - space b/w crus of helix & tragus. FOSSA TRIANGULARIS - in upper part of cavum conchae , infront of antihelix .

16. Cartilage – avascular , derives nutrients from perichondrium . 2 LIGAMENTS – Anterior ligament Posterior ligament MUSCLES – EXTRINSIC – Auricularis anterior ,posterior, superior (connect the auricle to the skull and scalp and move the auricle as a whole) INTRINSIC - connect the different parts of the auricle

17. IMPO R T ANCE INCISURA TERMINALIS - This area is devoid of cartilage , can be used for giving incision for procedures in ear to avoid post- op perichondritis . LATERAL SURFACE – Skin is firmly adherent to perichondrium ; so more prone for frost bite. MEDIAL SURFACE – More of subcutaneous tissue , skin is loosely adherent to underlying cartilage ; so cysts like sebaceous cyst are common .

18. IMPORTANCE Stripping the perichondrium from the cartilage, as occurs following injuries that cause haematoma, can lead to cartilage necrosis with crumpled up ' boxer's ears '. Small pieces of skin from the lobule of the pinna are commonly used for demonstration of lepra bacilli to confirm the diagnosis of leprosy.

19. BLOOD SUPPLY ARTERIAL SUPPLY – External carotid artery Posterior auricular artery Anterior auricular branches of superficial temporal artery Superior auricular artery VENOUS DRAINAGE- Auricular veins correspond to the arteries of the auricle. Arteriovenous anastomoses are numerous in the skin of the auricle and are thought to be important in the regulation of core temperature

20. NERVE SUPPLY

21. LYMPHATIC DRAINAGE The posterior aspect of the pinna drains to nodes at the mastoid tip. The tragus and upper part of the pinna drain into pre- auricular nodes The remainder of the pinna drains to upper deep cervical lymph nodes.

22. EXTERNAL AUDITORY CANAL From concha of auricle to TM. 2.4 cm long , cartilaginous & bony parts .

23. “ S ” shaped - its outer part is directed upwards, backwards and medially while its inner part is directed downwards, forwards and medially. Therefore, to see the tympanic membrane, the pinna has to be pulled upwards, backwards and laterally so as to bring the two parts in alignment. In the neonate, there is virtually no bony external meatus as the tympanic bone is not yet developed, and the tympanic membrane is more horizontally placed so that the auricle must be gently drawn downwards and backwards for the best view of the tympanic membrane.

24. CARTILAGINOUS PART - Outer 1/3 rd of EAC , 8mm Fissure of santorini Skin – hair follicles , ceruminous , sebaceous glands BONY PART – Inner 2/3 rd of EAC , 16mm Isthmus Anterior Recess

25. ISTHMUS – narrowest part of canal lying medial to junction of bony & cartilaginous parts nearly 5 mm lateral to TM . The roof & posterior wall of EAC are shorter than floor & anterior wall ; thus TM fits obliquely in deeper end of the canal . ANTERIOR RECESS – Anterior wall of EAC goes sharply forward to the TM to form a blind pouch . TYMPANIC SULCUS - medial end of the bony canal is ma r k ed b y a g r o o v e, th e tympani c sulcu s , w h i c h i s absent superiorly.

26. IMPORTANCE ANTERIOR RECESS- cmn site for foreign body impaction lodgement. FURUNCULOSIS – outer cartilaginous canal WAX - impaction (deafness,irritation , itching , otalgia etc)

27. IMPORTANCE Skin lining TM & Bony canal has self cleansing property due to migration of keratin layer of epithelium from drum towards cartilaginous portion Loss of this property – keratosis obturans

28. IMPORTANCE Irritation of the auricular branch of the vagus in the external ear by ear wax or syringing may reflexly produce persistent cough, vomiting or even death due to sudden cardiac inhibition. On the other hand, mild stimulation of this nerve may reflexly produce increased appetite. Accumulation of wax in the external acoustic meatus is often a source of excessive itching, although fungal infection and foreign bodies should be excluded. Troublesome impaction of large foreign bodies like seeds, grains, insects is common .

29. RELATIONS

30. BLOOD SUPPLY ARTERIAL SUPPLY – derived from branches of the external carotid. The auricular branches of the superficial temporal artery supply the roof and anterior portion of the canal. The deep auricular branch of the first part of the maxillary artery supplies the anterior meatal wall skin and the epithelium of the outer surface of the tympanic membrane. The auricular branches of the posterior auricular artery pierce the cartilage of the auricle and supply the posterior portions of the canal. VENOUS DRAINAGE - The veins drain into the external jugular vein, the maxillary veins and the pterygoid plexus.

31. NERVE SUPPLY Anterior wall and roof: auriculotemporal (V3). Posterior wall and floor: auricular branch of vagus (CN X). Posterior wall of the auditory canal also receives sensory fibres of CN VII through auricular branch of vagus. IMP - In herpes zoster oticus, lesions are seen in the distribution of facial nerve, i.e. concha, posterior part of tympanic membrane and postauricular region.

32. LYMPHATIC DRAINAGE Anterior wall – pre-auricular LN Posterior wall – post auricular LN Floor – retroauricular LN

33. TYMPANIC MEMBRANE Thin semi-translucent membrane , pearly white in colour, oval in shape . Lies obliquely at an angle of 55°. VD- 10mm ; HD- 9mm Inner surface is convex Forms majority of lateral wall of middle ear cavity

34. Peripheral part is thicker & rounded (except in upper part ) - ANNULUS TYMPANICUS Annulus is attached at its circumference to tympanic sulcus which ends in a notch known as " NOTCH of RIVINUS " in upper part. MALLEOLAR FOLDS - anterior & posterior ; arising from notch of rivinus to lateral surface of malleus .

35. 2 PARTS PARS TENSA - largest part below malleolar folds Contains all 3 layers Central part is tented inwards at the level of tip of malleus and is called UMBO Antero-inferior - most illuminated part

36. PARS FLACCIDA (SHRAPNELL's MEMBRANE) - Triangular area above malleolar folds Thin , devoid of fibrous tissue & annulus. It fits into notch of rivinus.

37. 3 LAYERS 1) OUTER CUTICULAR/EPITHELIAL LAYER - It is continuous with skin of EAC 2) MIDDLE FIBROUS LAYER - The lamina propria of the pars tensa has radially oriented fibres in the outer layers and circular, parabolic and transverse fibres in the deeper layer. This arrangement probably accounts for the complex pattern of tympanic membrane displacement during sound stimulation. Radial fibres normally merge with annulus tympanicus In the pars flaccida, the lamina propria is less marked and the orientation of the collagen fibres seems random. 3) INNER MUCOSAL LAYER - It is continuous with middle ear mucosa

38. BLOOD SUPPLY ARTERIAL SUPPLY – OUTER SURFACE - deep auricular branch of maxillary artery INNER SURFACE - Anterior tympanic branch of maxillary artery Posterior tympanic branch of stylomastoid artery Inferior tympanic artery , branch of ascending pharyngeal artery Arteria nutricia incudomallea , a twig from middle meningeal artery

39. VENOUS DRAINAGE – OUTER SURFACE - external jugular vein INNER SURFACE - Transverse sinus & venous plexus around Eustachian tube

40. NERVE SUPPLY LATERAL SURFACE - Anterior half - auriculotemporal nerve Posterior half - auricular branch of vagus MEDIAL SURFACE- Tympanic plexus (tympanic branch of CN IX (Jacobson’s nerve)

41. Referenc E s Scott Brown’s otorhinolarynology , head & neck surgery Glasscock-Shambaugh surgery of the ear Gray’s Anatomy Diseases of ENT & HNS – PL Dhingra, Shruti Dhingra Textbook of ENT & HNS -P Hazarika, D.R.Nayak, R.Balakrishnan

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