Anatomy of ear and its clinical application !

1. Anatomy of
the Ear
Dr. Amit Jha
1st year PG Resident , ENT-HNS

2. Anatomy of Ear
Externalear
Middleear
Internalear

3. External Ear
• Pinna
• External auditory
canal
• Tympanic membrane

4. Parts of a pinna

5. HELIX
The prominent rim of the auricle is
called the helix

6. Anti
Helix
Another curved prominence
parallel with and in front of the
helix is called the
antihelix

7. Conca
the antihelix describes a
curve around a deep,
capacious cavity concha
- the upper
part cymba
conchae,
- the lower
part cavum
conchae

8. Ear lobule

9. Anti tragus
6

10. Pinna
Skin :- thin, closely adherent to
perichondrium on lateral surface covered with
fine hairs which has sebaceous glands (most
numerous in the concha and scaphoid fossa)
Cartilage :- Yellow elastic fibrocartilage absent
at lobule and deficient between crus of helix
and tragus( incisura terminalis )connected to
temporal bone by ligaments, 3 extrinsic & 6
intrinsic muscles.

12. Nerve supply

13. Blood & lymphatic supply of
pinna

14. External auditory canal
Extends from
concha to tympanic
membrane
Bonycartilaginous
canal 1/3 2/3

15. Cartilaginous part
8 mm in adults. Continuous with auricular
cartilage.
Deficient superiorly space is occupied by int.
ligament
Two deficiencies (fissures of Santorini) :-
infections from parotid and superficial mastoid can
enter the canal and vice-versa.
Skin :- thick, hair follicles , sebaceous and
ceruminous glands.

16. Bony part
• 16 mm in adults.
• Narrower
• Medial end marked by tympanic sulcus (absent superiorly).
• Most part by tympanic bone (lateral projection oftemporal
bones ) and superiorly by squamous bone.
• Notch of Rivinus- junction of tympanosquamous and
tympano mastoid suture lines.
2 constrictions :- 1) BC junction
2) 5 mm lateral to TM
Skin is thin, devoid of hair and ceruminous glands.

17. Clinical application :
• Hair Follices are present only in outer cartilaginous canal and
therefore furuncles are only seen in cartilaginous EAC .
• Foreign body impacted medial to bony isthmus of EAC are
difficult to remove
• The anterior recess of bony EAC acts as a ceespool for
discharge and debris

18. Foramen of Huschke:
• The foramen tympanicum , also known as foramen of Huschke,
• is an anatomical variation in the external acoustic canal (EAC),
• where a bony defect connects the EAC to the temporomandibular
joint
• Persistence of the foramen tympanicum may also predispose the
individual to the spread of infection or tumor from the external
auditory canal to the infratemporal fossa or vice versa.
• It is associated with herniation of soft tissues from the temporo
mandibular joint into the external auditory meatus,
• and with formation of fistula between the parotid gland and the
external auditory canal.

19. Blood supply of EAC
Post auricular artery
Superficial temporal
artery

20. Nerve supply of EAC
The auriculotemporal nerve (from the
mandibular branch of the trigeminal nerve)
provides sensory information from the anterior
wall and roof
The posterior wall and floor sensibility is
carried in the nerve fibres of the auricular
branch of vagus (Arnold nerve)
The tympanic plexus offerssome
contributions

21. Lymphatic drainage
Anterior wall :- Preauricular lymph nodes
Posterior wall :- LN at mastoidtip
Rest :- upper deep cervical lymph nodes

22. Venous Drainage of EAC :
•Venous drainage corresponds to the arterial
supply
•via posterior auricular and superficial
temporal veins,
•and empties into the external maxillary and
jugular veins,
• as well as the pterygoid plexus.

23. Tympanic membrane
Cone shaped, Thin, oval
disc shaped.
55 degree angled.
Longest diameter :- 9-10
mm (i.e. posterosuperior to
anterosuperior)
Shortest diameter :- 8-9
mm (perp. To longest
diameter)
Width :- 0.1 mm

25. Otoscopic view

26. Tympanic membrane
Circumference is thickened to
form tympanic annulus, which fits
in the groove tympanic sulcus
Tympanic sulcus is deficient
superiorly
Annulus becomes a fibrous band
which runs centrally as ant. and
post. malleolar folds to the lat.
process and handle of malleus.
This region is called as pars
flacida and the rest of tympanic
membrane is called as pars
tensa.

27. Tympanic membrane
Umbo :- maximum
depression seen at the
inf. tip of handle of
malleus.
Cone of light :-
radiating from umbo
into the anteroinferior
quadrant.

28. Layers of the TM
TM has 3 layers:-
Epithelial (outer)- continuous with
skin of EAC
Fibrous/lamina propria(middle) –
missing in upper part
Mucosal (inner) – continuous
with middle ear mucosa

29. Nerve supply of TM

30. Blood supply of TM

31. Lymphatic drainage of TM

32. Middle ear
Tympanic cavity –six
sided cavity
1.Epitympanum - above
malleolar folds of TM
2.Mesotympanum- medial to pars
tensa of TM
3.Hypotympanum- below the level
of TM
4.Posterior tympanum: Middle ear
cavity behind bony tympanic annulus
5.Anterior tympanum or Pro-
tympanum: Middle ear cavity in front
of bony tympanic annulus

33. Six sided cavity
Roof – separated from
Middle cranial fossa –
tegmen tympani
Floor – separated from
IJV – thin plate of bone
Anterior wall
Posterior wall
Medial wall
Lateral wall

34. Anterior wall
Structures passing are
1. Canal for chorda
tmpani .N
2. Canal for tensor
tympani .M
3. Eustachian tube
4. Ant malleolar ligament
5. Ant tympanic artery

35. Eustachian tube
Passage between tym. cavity &
nasopharynx
Runs downwards, forwards &
medially from middle ear at
45degree angle
36 mm long, two unequal cones
connected at apices
Lat. bony 1/3rd (12mm), widest-
tympanic end, at ant wall of tym.
cavity, narrowest-isthmus(diam.
0.5mm)
Med.Cart. 2/3rd(24mm),open
medially ,1-1.25cm behind & below
post. end of inf. turb. at nasoph.,
torus tubaris, behind it- pharyngeal
recess(fossa of Rosenmuller)

36. Posterior wall
Upper part – aditus which
leads to mastoid antrum
Below aditus triangular
projection processus
pyramidalis
Facial recess – supra
pyramidal recess
Sinus tympani – infra
pyramidal recess

37. Lateral wall
Separate external
ear from middle ear
Formed by TMand
squamous part of
temporal bone

38. Medial wall
Separate middle ear
from inner ear
Important structures are
1.Promontory
2.Bony lat Semi circular
canal
3.Oval window – closed by
footplate of stapes
4.Round window – closed
by secondary TM
5.Facial nerve

39. Contents of the middle ear
Ear ossicles
1. Malleus (hammer)
2. Incus (anvil)
3. Stapes (stirrup)
Muscles
1. Tensor tympani
2. Stapedius
Mucosal folds
Nerves
vessels

40. head
Malleus
neck
lateral process
anterior
process
manubrium
body
lenticular process
long
process
head
posterior
crus
Stape
s
Footplate(3
x1.4mm)
anterior crus
incudio-malleolar joint(synovial)
short
process
Incus

41. Muscles
• Stapedius origin- pyramid,
Insertion- into posterior part
of neck & upper part of
posterior crus, supplied by
small br. of FN
• Tensor Tympani origin-
walls of bony canal above
ET, cart.part of ET, greater
wing of sphenoid Insertion-
medial aspect of upper end
of handle of malleus
supplied by branch of
mandibular nerve

42. Nerves & vesselsof middle ear
Chorda tympaninerve
Tympanic plexus
Plexus of vessels of stylomastoidartery
Carotico tympanicartery

43. Middle ear spaces

44. Mastoid
3 importantparts
1.Aditus – connects
epitympanum with
mastoid
2.Antrum – largest air
cell in the mastoid bone
3. Mastoid air cells

45. Koerner septum
• The Koerner septum, also known as
the petrosquamous lamina or septum
• is a thin bridge of bone which divides the petrous and squamous
portion of the mastoid air cells at the level of the mastoid antrum.
• It represents the continuation and persistence of
the petrosquamous suture
• It is commonly eroded by middle ear cholesteatomas.

46. Mac Ewen’s triangle
Bounded by temporal line
of supra mastoid crest and
postero superior bony
meatal wall and tangential
line joining these two
-The mastoid antrum lies 1-2
cm deep to the triangle in
the adult and thus serves as
a landmark when
performing a cortical
mastoidectomy.

47. Trautmann’s triangle
Boundaries
•Superiorly: superior petrosal sinus
•Posteriorly: sigmoid sinus
•Anteriorly: solid angle (semi-circular canals)
•Pathway to posterior cranial fossa from mastoid cavity
& vice versa

48. Sino dural angle
Between tegmen
antri and sigmoid
sinus
- It is an important
landmark in mastoid
surgery.
- It is acute in primary
sclerosis and obtuse
in secondary sclerosis

49. Blood supply
Middle meningealartery
Maxillary artery
Asc pharyngealartery
Posterior auricularartery

50. Nerve supply & lymphatics
Sensory – tympanic br of 9th CN – Jacobson’s
nerve
Motor - tensor tympani muscle is supplied by
mandidular nerve and stapedius muscle is
supplied by facial nerve
Lymphatics – preauricularand
retropharyngeal lymph nodes

51. Internal ear
Labyrinth
Bony Membranous

52. Bony labyrinth
BONY
LABYRINTH
VESTIBULE
SEMICIRCULAR
CANALS
COCHLEA

53. Cochlea

54. Cochlea
The cochlea is partially
divided into an upper scala
vestibuli and lower scala
tympani by a thin bony shelf ,
osseous spiral lamina.
This division is completed by
the scala media. Its floor is
formed by the basilar
membrane. Reissner’s
membrane forms the roof of
the scala media

55. Membranous labyrinth
Membranous vestibular
labyrinth
1. Saccule
2. Utricle
3. Endolymphatic duct and sac
Membranous semi-circular
canal
Membranous cochlear
labyrinth

56. Blood supply internal ear

57. References :
• Scott-Brown's Otorhinolaryngology-Head and Neck
Surgery. Ed by Gleeson, Browning, Burton et al (7th Ed 2008;
Hodder Arnold).
• Cummings Otolaryngology-Head and Neck Surgery. Flint,
Haughey, Lund et al (5th Ed 2010; Mosby).
• Current Diagnosis & Treatment in Otolaryngology-Head
and Neck Surgery. Lalwani (3rd Ed 2011; McGraw-Hill
Medical).
• Otolaryngology and Head and Neck Surgery - Oxford
Specialist Handbooks in Surgery. Warner, Burgess, Patel et
al (1st Ed 2009; Oxford).
• Oxford Handbook of ENT and Head and Neck
Surgery. Corbridge & Steventon (1st Ed 2006; Oxford).
• McMinn's Clinical Atlas of Human Anatomy. Abrahams,
Boon, Spratt, Hutchings (6th Ed 2008; Mosby).