ANATOMY OF EXTERNAL EAR

BY: INDERDEEP SINGH ARORA

External Ear

PINNA EXTERNAL ACOUSTIC MEATUS

DEVELOPMENT OF EXTERNAL EAR At 4-6wks- External ear develops from 6

auricular Hillocks of His First 3 Hillocks arise from 1st

branchial arch Rest 3 Hillocks arise from 2nd

branchial arch

Contd…………………… At 8-9 wks Hillocks fuse to form

primordia of auricle At 20th wks the pinna achieve

adult shape Hillock 1-tragus Hillock 2-root of helix Hillock 3-crus of helix Hillock 4-antihelix Hillock 5-antitragus Hillock 6-lower helix,lobule

Contd………………………

The embryonic pinna begins caudal to the growing mandible and then it is placed more cephalad and posterior

By end of 2nd trimester,the pinna reach adult location at the side of neck

External auditory canal- Develops from 1st branchial cleft 1st branchial cleft-ectoderm-

dorsal and ventral portion Dorsal persists, ventral

disappears At 4th week ectoderm invaginates

and lies adjacent to endoderm of 1st pharyngeal pouch

At 5th week-mesoderm grows between ectoderm and endoderm

By 16th week –meatal plug forms, which remains solid till 21st wk

By 21-28 wks medial plate begins to degenerate

At birth floor of bony canal is partially ossified

The bony canal is ossified by 3-4yrs

Incomplete ossification in anteroinferior canal-foramen of Huschke

Pinna

SYN:AURICLE Bilaterally symmeteric cartilage

frame that helps in focussing and localising sound

2 SURFACES-LATERAL AND CRANIAL

LATERAL-irregularly concave,directed forwards

Landmarks of pinna

Helix Antihelix Darwin’s tubercle Fossa triangularis Scapha Concha- Cymba conchae Cavum conchae

Contd………………………..

Tragus Anti tragus Intertragic notch Lobule

Cranial surface Eminentia concha Eminentia triangularis

Cartilage of pinna

Yellow fibroelastic cartilage Parts- Spina helicis Cauda helicis Fissura antitragohelicis Sulcus antihelicis transversus Ponticulus

CONTD…………………

Cartilage is avascular Derives its nutrition from

perichondrium On lateral side skin is thin and

tightly attached On medial side skin loosely

attached with a layer of subdermal adipose tissue

Muscles of pinna

2 groups Extrinsic muscle Intrinsic muscle Extrinsic- Auricularis anterior Auricularis superior Auricularis posterior

Intrinsic muscle Helicis major Helicis minor Antitragus Tragicus Transverse auriculi

LIGAMENTS

Extrinsic Ligaments Anterior ligament-It runs from

tragus and spina helicis to root of zygomatic process

Posterior ligament-It runs from eminentia concha to outer surface of mastoid process

Blood supply

Branches of external carotid

Posterior auricular artery- Medial surface[except lobule] Conch Medial and lower portion of helix Lower part of antihelix

Anterior auricular branch of superior temporal artery

Upper portion of helix,antihelix Triangular fossa Tragus Lobule

LYMPHATIC DRAINAGE

From posterior surface –lymph node at mastoid tip

From tragus and upper part of anterior surface-preauricular nodes

Rest of the auricle-upper deep cervical nodes

Nerve supply Greater auricular [C2,C3]-medial

surface and posterior portion of lateral surface

Lesser occipital[C2,C3]-superior portion of medial surface

Auricular[Vagus X]-concha,eminentia concha and antihelix

Auriculotemporal[Vc mandibular]-tragus,crus of helix

Facial VII-small region in the root of concha

External auditory meatus

Extension-from the concha to the tympanic membrane

Length-approximately 2.4cm Volume-2ml Diameter-8mm Supporting framework- Cartilage-lateral 1/3rd

Bone-medial 2/3rd

Shape-’s’ shaped Directed inwards ,downwards,

forwards Cartilage part is 8mm long Medial border of cartilage

attached to body canal by fibrous bands

Bony canal 16mm long Narrower than cartilageneous

part Medial end of bony canal marked

by a groove,the TYMPANIC SULCUS,which is absent superiorly

Most of the bony canal made up of tympanic bone except roof which is formed by squamous bone

2 suture line exist Tympanosquamous [anteriorly] Tympanomastoid [posteriorly] 2 constrictions occur1. At the junction of cartilagenous

and bony portion2. Isthmus,5mm from the

tympanic membrane

Skin-keratinised squamous There is outward,oblique growth

of epidermis of canal skin Normal rate of migration is

0.1mm per day Cartilageneous portion -0.5-

1mmthick,dermisand subcut.layer contains hair follicle and glands

Glands-ceruminous [modified apocrine sweat glands],sebaceous glands

Bony canal skin-0.2mm,attached to periosteum

Blood supply

Branches of external carotid Auricular branch of superficial

temporal-roof and anterior portion

Deep auricular branch of maxillary artery-anterior meatal wall

Auricular branch of posterior auricular artery-posterior portion

Veins drain into external jugular vein,maxillary vein,pterygoid plexus

Relations

Superiorly-middle cranial fossa Posteriorly-mastoid air cells Medial-middle ear Anterior-temporomandibular joint superficial temporal

vessel auriculotemporal nerve parotid gland preauricular lymph node

Inferiorly-jugular bulb external carotid facial nerve styloid process parotid digastric muscle

Nerve supply

Anterior wall and roof-auriculotemporal[V3]

Posterior wall and floor-auricular branch of vagus[X]

Posteriosuperior wall receives sensory fibers of facial nerve through auricular branch of vagus

Lymphatic drainage

Similar to that of pinna i.e preauricular nodes,upper deep cervical lymph nodes

surgical importance Pinna as a source of graft

material for reconstruction surgeries of middle ear

Conchal cartilage can be used to correct the depressed Nasal Bridge and Nasal Ala

Incisura Terminalis- This is the area where no

cartilage between tragus and helix

An incision made in this area will not cut through cartilage and is used for Endaural approach in surgery of ear

Contd…………………………… Syndromes associated with

arrested development of 1st and 2nd brachial arch deviation leading to retroverted,malformed and low set,more anteriorly placed pinna are Treacher Collins Syndrome,Hemifacial Microsomia,Nager Synd,Klippel Fleil Synd

Contd……. Disturbances in external ear

growth associated with other systemic defects-

CHARGE,VATER,VACTERL,Townes Brocks syn.,Winderwanck S.,Brachio-oto-renal S.

1st branchial cleft anomalies result in early disruption of hillock fusion

Duplicated ext. auditory canal Persistent embryonic tract-

callaural fistula

Cat’s ear- Auricle is folded forward and downward.

Wildermuth ear- Antihelix is more prominent then helix.

Mozart ear- Enlarged antihelix that is continuous with the helix.

Lop ear/bat ear-disrupted cartilage formation of helix,fold of antihelix is absent,.angle of projection is more

Cup ear-disrupted cartilage formation of concha

Microtia-associated with Hemifacial Microsomia,Gondenhar syn.,oculo auriculo vertebral dysplasia

Macrotia-associated with Marfan syn.,Fragile X syn.

Most exagerrated portion is scaphoid.

Anotia-complete absence of pinna

Absent lobule-seckel syndrome Auricular cleft-associated with

holoprocencephaly Melotia-ear located on cheek Synotia-Bow-Tie ear-AGNATHIA

SYNOTIA MICROSTOMIA SYN. Auricular appendages-located

infront,behind,within,on the lobule.

On medial layer of pinna there is subdermal adipose tissue which allows dissection during pinnaplasty surgery.

Superior auricular artery connects superficial temporal & post. Auricular artery. This branch provides reliable vascular pedicle for retro auricular flaps.

By 5-6 yrs of age auricle is 80% of adult size. This is appropriate time for surgical management of deformities of pinna.

BOXER’S EAR Atresia of EAC- Failure of

canalisation of ectodermal core that fills dorsal part of first branchial cleft.

Foramen of Huschke- Ant. Inferior part of bony canal may present deficiency in children upto age of 4 or more, permitting infection to and from the parotid.

Fissure of Santorini- 2-3 in no. in cartilaginous portion , through them the parotid or mastoid infection can enter EAC or viceversa.

Tympanomastoid and tympanosquamous sutures are landmarks for vascular stripe incisions.

Thank you