This document provides information on the anatomy of the ear. It describes the three parts of the ear - outer, middle, and inner ear. The outer ear includes the auricle, external acoustic meatus, and eardrum. The middle ear contains the tympanic cavity lined with mucosa and contains the three ossicles (malleus, incus, stapes) and two muscles (tensor tympani and stapedius). The inner ear houses the organs of balance and hearing. The document then provides detailed information on the anatomy and features of the tympanic cavity such as its boundaries, contents, blood supply, and clinical correlations.

1. EAR
• DR. SUNDIP CHARMODE
• ASSOCIATE PROFESSOR
• DEPARTMENT OF ANATOMY
• AIIMS RAJKOT

2. EAR: THREE PARTS
• Sense of Hearing
– Made up of:
• Outer ear
• Middle ear
• Inner ear
• Ear also functions
as sense of
equilibrium

3. OUTER (EXTERNAL) EAR
• 3 parts
• Auricle (Pinna)
– Funnel-like structure
• External Acoustic
Meatus (External
Auditory Canal)
– S-shaped tube
• Eardrum (tympanic
membrane)
– Cone shaped
– Sometimes
considered part of
middle ear

4. AURICLE
• Helps collect sound
waves traveling
through the air and
directs them into the
external acoustic
meatus.

6. EXTERNALACOUSTIC MEATUS
• As sound waves enter, they change the
pressure on the eardrum.

7. EXTERNALACOUSTIC MEATUS
• It extends from
the bottom of
concha to the
tympanic
membrane
• 24 mm long in
adults

9. EXTERNALACOUSTIC MEATUS
• The external ear describes an S shaped curve and consist
of 3 parts:
• Pars Externa: directed upwards, forwards and medially
• Pars Intermedia: directed upwards, back and medially.
• Pars Interna: directed downward, forward and medially

10. EXTERNALACOUSTIC MEATUS -
SUBDIVISIONS
Lateral one-third – 8 mm –
cartilaginous part
Medial two-thirds – 16
mm – bony part

11. CARTILAGINOUS PART
• Continuous with the
cartilage of the auricle.
• In upper and posterior part
of meatus, cartilage is
absent and is replaced by
fibrous membrane.
• Sometimes, three or more
fissures of Sartorini, affect
the anterior wall of
cartilaginous part.

13. BONY PART
• Composed of tympanic plate of temporal bone below and
in front, and
• Squamous part of temporal bone in above and behind.
• A Tympanic Sulcus is present as the medial end of
meatus, where tympanic membrane is attached
obliquely.
• Floor and anterior wall of meatus is longer than the roof
and posterior wall.

15. CONSTRICTIONS
• Two:
• At the junction of the bony
and cartilaginous part
• At the isthmus in the bony
part which lies about 2 cm
deep to the concha. It is the
narrower of the two.

16. LINING EPITHELIUM OF EAM
• Lined by skin, which is continuous externally with
the skin of the auricle and internally with the cuticular
layer of the tympanic membrane.
• The skin is adherent to the bones and cartilage of the
meatus, hence collection of inflammatory exudate
beneath the skin produces severe pain due to tension.

17. RELATIONS OF EAM
• In front: head of mandible separated by a part of
parotid gland
• Above the bony part: floor of middle cranial fossa
and epitympanic recess of tympanic cavity
• Postero-superior to the bony part: mastoid antrum
separated by mastoid air cells and a thin plate of bone
of only 1- 2mm thick.

19. BLOOD SUPPLY
• Arterial supply:
– Posterior auricular branch of ECA
– Deep auricular branch of maxillary artery
– Anterior auricular branches of superficial temporal artery
• Venous drainage: external jugular vein and
maxillary veins – into pterygoid venous plexus.

20. NERVE SUPPLY
• Roof and anterior wall: auriculo-temporal nerve
• Floor and posterior wall: auricular branch of vagus
nerve ( nerve of alderman)

21. DEVELOPMENT
• It is developed from funnel shaped ectodermal
invagination from the dorsal part of the first branchial
cleft.

22. CLINICAL CORRELATES
• Excessive accumulation of ear wax sometimes blocks
the meatus and impedes the transmission of sound
vibrations.
• Inflammation of EAM is painful as the skin is
adherent to the adjacent structures and subcutaneous
collection produces tension.

23. TYMPANIC MEMBRANE
• The ear drum is oval, semi
transparent, pearly grey tri-
laminar membrane and
separates the EAM from
tympanic cavity.
• Max. diameter : 9-10mm
• Min. diameter: 8-9 mm

24. POSITION
• The membrane is places obliquely
at an acute angle of 55 degrees
with the floor of EAM.
• In newborns, the TM is almost
horizontal.
• The circumference of TM is made
up of fibro-cartilaginous ring
which is attached to the sulcus of
tympanic plate at the bottom of
EAM.

25. POSITION
• The sulcus is deficient
above, from the two
ends of which the
anterior and posterior
malleolar folds converge
to the lateral process of
malleus in the upper part
of tympanic membrane.

26. SUBDIVISIONS
• The malleolar folds divided the TM into two parts:
• Pars flaccida: small, triangular, lax area above the
malleolar folds. Sometimes it presents a small
perforation.
• Pars tensa: occupies the rest of the membrane which is
rendered taut by the attachment of the handle of malleus
and by the disposition of radiating fibers of the
intermediate layer from the handle.

29. SURFACES
• Lateral surface:
– concave,
– directed down, forward and laterally
• Medial surface:
– Convex
– Bulges towards the tympanic cavity
– Maximum point of convexity – Umbo
– This surface received the attachment of handle of malleus
which intervenes between the fibrous and mucous layers.

30. SURFACES
• Medial surface:
– The handle of malleus is crossed by chorda tympani nerve
which runs forward between the fibrous and mucous layers
of membrane at the junction of pars flaccida and pars tensa.

31. STRUCTURE
• From outside inwards, TM consist of three strata:
• Outer cuticular layer:
– Lined by hairless, keratinized stratified squamous epithelium,
and is continuous with skin of EAM.
– The cuticular layer is devoid of dermal papillae
• Intermediate fibrous layer:
– Consists of outer radiating and inner circular fibers
– The radiating fibers diverge from the handle of malleus to
periphery.
– The circular fibers are abundant in periphery and scanty in the
centre

32. STRUCTURE
• Inner mucous layer:
– lined by simple columnar or squamous epithelium with
patches of ciliated cells in upper part of membrane.

33. BLOOD SUPPLY
• Arterial supply:
1. Deep auricular branch of maxillary artery which
ramifies beneath the cuticular layer.
2. Stylomastoid branch of posterior auricular and
anterior tympanic branch of maxillary arteries : both
supply the mucous layer.
• Venous drainage:
• Outer layer – external jugular vein
• Inner layer – transverse sinus – pterygoid venous
plexus

34. NERVE SUPPLY
• The cuticular layer is supplied by:
1. Auriculotemporal nerve in the upper and anterior
part of membrane
2. The auricular branch of vagus nerve in lower and
posterior part of TM
• The mucous layer is supplied by glossopharyngeal
nerve through tympanic plexus.

35. DEVELOPMENT
• The TM is developed from three sources:
1. Cuticular layer develops from ectoderm of the dorsal
end of first branchial arch.
2. Intermediate fibrous layer is derived from mesoderm of
adjoining branchial arches.
3. Inner mucous layer – endoderm of tubo-tympanic recess
formed by fusion of dorsal ends of 1st and 2nd
pharyngeal pouches.

36. CLINICAL CORRELATES
• A surgical incision (myringotomy) should be made in
postero-inferior quadrant in order to avoid injury to
chorda tympani nerve and the ossicles of the ear.

37. THANK YOU

38. DR. SUNDIP CHARMODE
ASSOCIATE PROFESSOR
DEPARTMENT OF ANATOMY
AIIMS RAJKOT
TYMPANIC
CAVITY

39. INTRODUCTION
• Lies within petrous
part of Temporal bone.
• Filled with air and
lined by mucous
membrane.
• It assumes full adult
size at birth.

40. COMMUNICATIONS
• In front: lateral wall of
nasopharynx via auditory tube
• Behind: mastoid antrum via
aditus to mastoid antrum.
• Sandwiched between external
and inner ear.
• Biconcave shape

43. DIMENSIONS
• Vertical: 1.5 cm
• Antero-posterior: 1.5
cm
• Transverse:
i. At Roof: 0.6 cm
ii. At Centre of
Tympanic
membrane: 0.2 cm
iii. At floor: 0.4 cm

44. SUB-DIVISIONS
 Epi-tympanum (Attic) :
Above Tympanic
membrane
 Meso-tympanum :
Opposite the Tympanic
membrane, narrowest
part
 Hypo-tympanum : Below
the Tympanic membrane

45. BOUNDARIES
 It is roughly cuboidal and presents six walls :
• Roof
• Floor
• Anterior wall
• Posterior wall
• Medial wall
• Lateral wall

48.  Roof is wider than floor.
 Anterior wall is narrower than posterior wall.
 Medial and lateral walls project their
convexities towards the Tympanic cavity.
BOUNDARIES

49. ROOF
• Tegmen tympani: thin plate of petrous temporal
bone.
• Intervenes between tympanic cavity and middle
cranial fossa.
• The roof is pierced by lesser and greater petrosal
nerves.
• In young: tegmen tympani may remain unossified.
• In adults: veins from tympanic cavity drain into
superior petrosal sinus through petro-squamous
suture.

52. FLOOR
• Jugular fossa: on undersurface of petrous part of
temporal bone.
• It is related to superior bulb of internal jugular vein.
• Tympanic branch of glossopharyngeal nerve pierces
the floor, enters the TC, through an aperture
between jugular fossa and carotid canal lower
opening.

55. ANTERIOR WALL
• In the lower part, it is bounded by the posterior wall
of carotid canal, which contains internal carotid
artery and a plexus of sympathetic nerves around the
artery.
• This part of wall is perforated by superior and inferior
carotico-tympanic vessels and nerves.

56. ANTERIOR WALL
• The upper part of anterior wall presents two parallel
bony canals one above the other.
• Upper canal for tensor tympani muscle.
• Lower canal for the bony part of auditory tube.
• Both canals pass forward, downward and medially.
• A bony partition intervenes between the two canals and
extends backward along the medial wall of tympanic
cavity.

57. POSTERIOR WALL
• It is wider above than below:
1. Aditus to Mastoid antrum: through which the
epitympanic part of tympanic cavity
communicates with mastoid antrum.
2. Fossa Incudis: a small depression close to lower
part of aditus. The short process of incus is
suspended from fossa by a ligament.

60. POSTERIOR WALL
3. Vertical Bony canal for facial nerve: it descends
up to stylomastoid foramen.
4. Hollow Pyramidal eminence: projects forward
from upper part of facial canal and contains
stapedius muscle and its nerve supply.

62. MEDIAL WALL
 This wall faces towards the bony labyrinth of Internal ear.
1. Promontory: basal turn of cochlea of internal ear.
2. Fenestra Vestibuli (Fenestra Ovalis): a reniform
aperture behind and above the promontory. Closed by
base of stapes and annular ligament.
3. Fenestra Cochlea (Fenestra Rotunda): small window
below and behind the promontory. Closed by trilaminar
secondary tympanic membrane.

64. MEDIAL WALL
4. Sinus tympani – depression behind promontory
and indicates the position of the ampulla of
Posterior Semicircular canal.
5. Oblique part of bony facial canal:
6. Processus Trochleariformis: hook like process.
Tendon of tensor tympani turns laterally around this
process before inserting on the handle of malleus.

68. LATERAL WALL
 Most of the wall is formed by mucous
membrane covering Tympanic membrane.
 Epi-tympanic part is formed by :
1. Squamous part of Temporal bone
2. Head and anterior process of Malleus
3. Body and short process of Incus

70. CONTENTS
1. Three ossicles: malleus, incus and stapes
2. Two muscles: tensor tympani, staepdius
3. Sex sets of arteries
4. Four sets of nerves

72. ARTERIES
1. Stylomastoid branch of Posterior auricular
artery
2. Anterior Tympanic branch of Maxillary artery
3. Petrosal branch of Middle Meningeal artery
4. Superior Tympanic branch of Middle
Meningeal artery
5. Branches from Ascending Pharyngeal artery
and artery of Pterygoid canal.
6. Tympanic branches of ICA

73. NERVES
1. Superior and Inferior sets of Carotico-
tympanic nerves, from Sympathetic plexus
around ICA.
2. Tympanic branch of Glossopharyngeal nerve
3. Chorda-tympani nerve
4. Facial nerve

74. APPLIED ANATOMY
1. Otitis media
2. Myringotomy
3. Otosclerosis
4. Mastoid drainage

75. THANK YOU