Download - Anatomy of External Ear
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.
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