The document summarizes the development of the ear structures from the first and second pharyngeal arches and pouches. It describes how the auricle, external auditory canal, tympanic membrane, middle ear bones, middle ear cavity and inner ear develop from the embryonic tissues. It also provides details on the anatomy, blood supply and innervation of the ear structures.

1. Dr Ajeet Kumar Khilnani
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2. • Auricle develops from first branchial cleft (6
tubercles, Hillocks of His)
• Tragus from the first tubercle
• Rest of the pinna from the remaining 5
tubercles
• Pre-auricular sinus is due to faulty fusion of
1st and 2nd tubercles
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3. • External Auditory Canal (EAC) from first
branchial cleft. It is fully formed by 28th week
of gestation
• Tympanic Membrane (TM) develops from all
three germinal layers
Outer epithelial layer- Ectoderm
Middle fibrous layer- Mesoderm
Inner mucosal layer- Endoderm
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4. • Middle ear cleft (Eustachian tube, middle ear,
attic, antrum and mastoid air cells) develops
from tubotympanic recess from first and
partly from second pharyngeal pouch
• Malleus and incus from mesoderm of first
arch
• Stapes from second arch (except the footplate
and annular ligament which are derived from
otic capsule)
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5. • Inner ear develops from the ectoderm in the
region of hind brain (auditory placode)
• Cochlea develops by 20th week and the fetus
can hear in the womb!!
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6. It consists of
Auricle or pinna
External auditory canal
Tympanic membrane
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8. • Pinna is made up of a single piece of yellow
elastic cartilage
• Incisura terminalis- site of endaural incision
• Cartilage from tragus, perichondrium and fat
used as a graft material
• Conchal cartilage is used for correction of
depressed nasal bridge (Augmentation
rhinoplasty)
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9. • It is not straight, so pinna is pulled UBL to see
the TM
• Outer one-third (8 mm) is cartilaginous
• Fissures of Santorini (b/w EAC and parotid)
• Skin contains hair, ceruminous and
pilosebaceous glands which secrete wax.
• Furuncle seen in outer canal
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10. • Inner two-thirds (16 mm) is bony
• Isthmus is 6 mm lateral to TM: Foreign bodies
medial to it are impacted
• Foramen of Huschke
• Lining skin is devoid of hair and ceruminous
glands
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11. • 9-10 mm tall, 8-9 mm wide, 0.1 mm thick
• Two parts: Pars Tensa (PT) and Pars Flaccida
(PF) (Shrapnel’s membrane)
• Annulus tympanicus (outer fibrocartilaginous
ring)
• Notch of Rivinus: Annulus absent here
• 3 layers: Outer epithelial
Middle fibrous (not organised in PF)
Inner mucosal
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14. • Lateral surface
Anterior half: Auriculotemporal (V3)
Posterior half: Auricular branch of Vagus
• Medial Surface
Tympanic branch of CN IX (Jacobon’s
nerve)
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15. • It is formed by
Eustachian tube
Middle ear
Attic
Antrum
Mastoid air cells
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17. • It is like a six-sided box
• Divided into 3 parts
Epitympanum (attic)
Mesotympanum
Hypotympanum
• Portion of middle ear around the Eustachian
tube orifice is sometimes called
protympanum
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20. The roof
• Formed by tegmen tympani
• Separates middle ear from middle cranial
fossa
The floor
• Separates middle ear from jugular bulb
The anterior wall
• Separates middle ear from internal carotid
artery
• Two openings: Upper for tensor tympani
Lower for Eustachian tube
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21. The posterior wall
• Pyramid: Bony projection where stapedius
tendon appears to get attached to neck of
stapes
• Aditus: Opening through which attic
communicates with antrum
• Facial recess (posterior sinus): Depression
lateral to pyramid. It is the site for posterior
tympanotomy
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22. The medial wall
• It is formed by the labyrinth
• Promontory: Bulge due to basal coil of
cochlea
• Oval window (OW): For stapes footplate
• Round window (fenestra cochleae)
• Canal for CN VII: Above the oval window
• Processus cochleariformis: Hook like
projection anterior to OW. The tendon of
tensor tympani turns here to get attached to
neck of malleus
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23. • The cochleariform process also marks the
genu of CN VII, hence an important surgical
landmark in facial nerve surgery
• Sinus tympani: Deep recess medial to
pyramid. It is bounded by ponticulus above
and subiculum below
The lateral wall
• Formed by TM and scutum (bony outer attic
wall)
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25. • Three types of cells
Well pneumatised or cellular
Diploetic
Sclerotic or acellular
• Depending on the position they can be
zygomatic, tegmen, perisinus, retrofacial,
perilabyrinthine, peritubal, tip cells
• Korner’s septum: Petrosquamosal suture
persist as a bony plate
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31. • Tensor tympani
Attaches to neck of malleus
Tenses the TM
Develops from first arch
Supplied by V3
• Stapedius
Attaches to neck of stapes
Dampens very loud sounds
Develops from second arch
Supplied by CN VII
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32. • Tympanic Plexus
- Tympanic branch of glossopharyngeal
- Sympathetic fibres from the plexus round
the ICA
• Lies on the promontory
• Carries secretomotor fibres for the parotid
gland
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33. • 6 arteries
- Anterior tympanic branch of maxillary artery
(TM)
- Stylomastoid branch of posterior auricular
artery (middle ear and air cells)
- Petrosal branch of middle meningeal artery
- Superior tympanic branch of middle
meningeal artery
- Branch of artery of pterygoid canal
- Tympanic branch of internal carotid
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