1. ANATOMY & EMBRYOLOGY
OF THE
EXTERNAL & MIDDLE EAR
Dr. Mohammed Shafeeq

2. EAR:
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External Ear
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Middle Ear
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Internal Ear
(Labyrinth)

3. Embryology – External Ear
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develops around the
first branchial arch

4. AURICLE:
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Around 6th week of IUL
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Developed from a series of
small cartilaginous tubercles
around 1st pharyngeal groove -
'Hillocks' or 'Tubercles of His'

5. ●
First Pharyngeal Arch
1) Tragus
●
Second Pharyngeal Arch
2) Crus of helix
3) Helix
4) Anti helix
5) Anti tragus
6) Ear lobule

6. ●
Anomalies of Auricle (Pinna):
1) Preauricular sinus
2) Anotia
3) Bat ear deformity

7. EXTERNAL ACOUSTIC CANAL:
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●
●
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Develops from surface ectoderm covering the dorsal
end of 1st pharyngeal groove
Meatus deepens by proliferation of its ectoderm
Anteriorly placed bud of epithelial cells expand
vertically to form the skin which will cover the future
TM
Clumps of cells then opens up as a slit to form the
canal lumen and produce the pars tensa and deep
external canal epithelium

8. ●
Anomalies of EAC:
1) Atresia
2) Changes in curvature of canal
3) Stenosis

9. ●
Tympanic Membrane:
1) Inner mucosal layer from ENDODERM
2) Middle fibrous layer from MESODERM
3) Outer epithelial layer from ECTODERM

10. MIDDLE EAR - Embryology
●
st
rd
1 pharyngeal develops by 3 week of IULof
which,
- proximal narrow part forms Eustachian Tube
- distal dilated part forms tubotympanic recess,
later to Middle Ear Cleft
- in later fetal life, diverticulum appears from
tubotympanic recess forming the Mastoid Antrum

11. ●
OSSICLES:
- Anson in 1959
- from 1st and 2nd arch cartilages
- 1st arch (Meckel's) cartilage: head of malleus &
body of incus
- 2nd arch (Reichert's) cartilage: handle of malleus,
long process of incus, crurae of stapes
- Otic capsule: foot plate of Stapes

12. Middle Ear Spaces & Folds:
numerous spaces and folds are formed when mucous
membrane of tubotympanic recess encircle the ossicles.
Attic Compartment:
- Anterior Compartment
- PosteriorCompartment
Compartments of
Mesotympanum:
- Anterior Malleolar Fold
- Posterior Malleolar Fold
- Tensor Tympani Fold

13. ●
Prussak's Space:
- potential space which may first to involve during
extension of Cholesteatoma,
- bounded by,
laterally, Shrapnell's membrane
medially, Neck of Malleus
superiorly, fibres of lateral malleolar fold
inferiorly, lateral process of malleus

14. ANATOMY – External Ear
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Auricle / Pinna
●
External Acoustic Canal
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Tympanic Membrane

15. ●
Auricle (Pinna)
- elastic fibrocartilage, two surfaces:
medial & lateral surface
- Lateral surface –
characteristic prominences and depressions
- Helix – most prominent outer part
- Anti Helix – fold in front of helix
- Concha – in front of anti-helix, 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 & anti helix
- Incisura Terminalis – space b/w crus of helix and tragus

16. ●
Cartilage – avascular, derives nutrients from
perihondrium
●
Trauma – 'Boxer's Ear'
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Two ligaments
- Anterior Ligament
- Posterior Ligament
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Muscles
- Extrinsic Muscles
- Auricularis Anterior
- Auricularis Posterior
- Auricularis Superior
- Intrinsic Muscles

17. ●
Blood Supply
- Posterior Auricular Artery
- Anterior Auricular branches of Superficial Temporal A
- Superior Auricular Artery
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Nerve Supply
- Greater Auricular N
- Lesser Occipital N
- Auriculotemporal N
- Auricular branch of Vagus N (Arnold's N)
- fibres from Facial N

18. ●
External Auditory Canal:
- from concha of auricle to TM
- 2.4cm long, two parts – outer Cartilaginous and inner Bony part
●
Cartilaginous Part:
- outer 1/3 of EAC, 8mm
- two deficiencies – 'Fissures of Santorim'
●
Bony Part:
- inner 2/3 of EAC, 16mm
- Isthmus
- Anterior Recess
- Foramen of Huscke
- Tympanic Sulcus

19. ●
Tympanic Membrane:
- medial end of EAC, partition b/w EAC and middle ear
- obliquely set, forming an angle of 55 degree
- 9-10mm tall, 8-9mm wide and 0.1mm thick
Two parts:
- Pars Tensa
- Pars Flaccida ( Shrapnel's Membrane )
Three layers:
- Outer Epithelial Layer
- Middle Fibrous Layer
- Inner Mucosal Layer

20. ●
Pars Tensa:
- Annulus Tympanicus
- Umbo
- four quadrants
- 'cone of light'
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Pars Flaccida (Shrapnel's Membrane):
- Anterior mallelolar fold
- Posterior malleolar fold
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Nerve Supply:
- Auriculotemporal N (Ant half of lat surface)
- Auricular Br of Vagus N (Post half of lat surface)
- Tympanic br of CN IX – Jacobson's N (med surface)

21. ANATOMY – Middle Ear
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●
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Middle Ear Cleft – Middle ear(Tympanic
cavity), Aditus, Antrum, Mastoid air cells
Middle Ear/Tympanic cavity: irregular, air
filled space within the temporal bone b/w TM
laterally and osseous labyrinth medially.
Contains auditory ossicles, intratympanic
muscles

22. ●
Middle Ear: 3 compartments
- epitympanum (attic) :
lies above level of malleolar fold
- hypotympanum :
lies below level of tympanic sulcus
- mesotypmanum :
lies opposite pars tensa

23. 6 surfaces – Roof, Floor, Medial, Lateral,
Anterior, Posterior
●
●
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Roof – Tegmen tympani
Floor – thin plate of bone seperating
hypotympanum from dome of jugular bulb
Anterior wall – thin plate of bone seperates
from Internal Carotid A.
Two openings –
lower one for Eustachian tube,
upper for canal of tensor tympani

24. ●
Posterior wall –
lie close to mastoid air cells, and has following
structures:
- Aditus
- Fossa Incudis
- Pyramid
- Facial Recess
●
Lateral wall - TM
- Scutum

25. ●
Medial wall – separates tympanic cavity from
middle ear
- Promontory
- Oval window
- Round window
- Subiculum
- Ponticulus
- Canal for facial N
- Processus cochleaformis
- Sinus tympani

26. ●
Mastoid Antrum:
Air containing space in upper part of mastoid and
communicates with attic through aditus
- Roof: tegmen antri
- Lateral wall: plate of bone on an avg 1.5cm thick in
adults
●
MacEwen's (suprameatal) triangle: bounded by
- temporal line
- posterosuperior segment of bony EAC
- line drawn tangent to external canal

27. ●
Aditus:
- opening through which attic communicates with
antrum.
- Bony prominence of horizontal canal medially,
- fossa incudis laterally
- Facial N course below aditus

28. ●
Contents of Tympanic Cavity:
- Ossicles – Malleus, Incus, Stapes
- Intratympanic muscles – Tensor tympani,
Stapedius
- Chorda tympani,
- Tympanic plexus

29. ●
Ossicles of middle ear
- MALLEUS:
head, neck, handle(manubrium),
lateral and anterior process
Head and neck of malleus lie in
attic.
Manubrium lies embedded in fibrous layer of TM
Lateral process forms a projection and attaches to ant.
& post. malleolar folds

30. - INCUS:
- body, short process, long process
- body and short process lies in attic
- long process hangs vertically &
attaches to head of stapes
- STAPES:
- head, neck, Ant. & Post. Crura,
Footplate
- footplate is held in oval window by annular ligament

31. ●
INTRATYMPANIC MUSCLES:
Tensor tympani - attaches to neck of malleus
- tenses tympanic membrane
- derived from 1st arch
- supplied by branch of
Mandibular N

32. Stapedius - attaches to neck of stapes
- helps to dampen loud sound,
preventing noise trauma to
inner ear
- derived from 2nd arch
- supplied by branch of Facial N

33. ●
Tympanic Plexus:
- lies in the promontory
- formed by:
- tympanic br of gloosopharyngeal N
- sympathetic fibres from plexus around ICA
- supplies innervation to:
- medial surface of TM, tympanic cavity, mastoid air
cells & bony eustachian tube
- carries secretomotor fibres for the parotid gland

34. ●
Chorda tympani N:
- Br of Facial N enters the middle ear through posterior
canaliculus
- runs on medial surface of TM b/w HOM and long
process of incus
- carries taste sensation from Ant. 2/3rd of tongue
- secretomotor fibres to submaxillary and sublingual
salivary glands

35. ●
Blood Supply of Middle Ear:
Anterior tympanic br of Maxillary A
- supplies TM
Stylomastoid br of Post Auricular A
- supplies middle ear and mastoid air cells
Minor vessels:
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Petrosal br of middle meningeal A
Sup tympanic br of middle meningeal A
Branch of Artery of pterygoid canal
Tympanic br of ICA
Veins:
drain into pteryoid venous plexus & Superior petrosal veins

36. Thank You....