External ear,tympanic membrane and auditory tube - Lecture by Dr.N.Mugunthan.M.S.,Associate Professor, Mahatma Gandhi Medical College & Research Institute, Pondicherry, Sri Balaji Vidyapeeth University.

1. EXTERNAL EAR, TYMPANIC MEMBRANE &
AUDITORY TUBE
Lecture By
Dr.N.Mugunthan. MBBS.,MS.,DNB.,MNAMS.,PhD.,MBA (Hosp.Adm.).,
Associate Professor
MGMC & RI

2. LEARNING OBJECTIVES
Subdivisions of ear
Concept of hearing
External ear (auricle & external auditory
meatus)
 Tympanic membrane or ear drum
Auditory tube
Development of external ear & it’s anomalies
Applied anatomy
©Dr.N.Mugunthan

3. Ear
• Ear is an organ of hearing
• Human ear is most sensitive to sound frequency
ranging between 1500 to 3000 Hertz
3 Parts
1. External ear
2. Middle ear
3. Internal ear
©Dr.N.Mugunthan

4. ©Dr.N.Mugunthan

5. ©Dr.N.Mugunthan

6. External ear
1. Auricle
2. External acoustic
meatus
Auricle or pinna
Single piece of yellow
elastic cartilage
continuous with
cartilaginous part of
ext.acoustic meatus
Absent in lobule of ear
©Dr.N.Mugunthan

7. Features of auricle
 Helix
 Antihelix
 Tragus
 Antitragus
 Concha
 Cymba conchae
 Scaphoid fossa
 Triangular fossa
 lobule
©Dr.N.Mugunthan

8. Muscles of auricle
Extrinsic muscles (move the auricle
as a whole)
 Auricularis superior
 Auricularis posterior
 Auricularis anterior
Intrinsic muscles (modify the shape
of pinna)
 Helicis major
 Helicis minor
 Tragicus
 Antitragicus
 Transversus auriculae
 Obliquus auriculae
Nerve supply :– Temporal branch &
post.auricular branches of facial
nerve
©Dr.N.Mugunthan

9. External acoustic meatus / auditory canal
Extent: bottom of concha to
tympanic membrane
Length: 24mm (shorter in child)
Subdivisions:
1. Cartilaginous part -lat.1/3
(8mm)
2. Bony part – med.2/3
(16mm)
©Dr.N.Mugunthan

10. Lateral end :– bottom of concha
Medial end :- tympanic sulcus for
tympanic membrane -attached
obliquely
Roof
Floor
Ant.wall
Post.wall
Lined by skin continuous with
cuticular layer of tympanic
membrane
Ceruminous glands – cerumen
(wax) to prevent maceration of
epithelium & warm humid for
effective vibrations of
tympanic membrane
External auditory canal cont…
©Dr.N.Mugunthan

11. Blood supply :
1. Anterior auricular (Superficial Temporal Artery)
2. Posterior auricular (ECA)
3. Deep auricular (Maxillary)
Venus drainage:
• Drain into EJV, maxillary vein & pterygoid plexus
Nerve supply:
Roof & ant.wall- auriculotemporal nerve
Floor & post.wall – auricular branch of vagus
(alderman’s nerve)
External auditory canal cont…
©Dr.N.Mugunthan

12. Applied anatomy
Otitis externa
Wax
Ear wax –irritate the
auricular branch of vagus
(Alderman’s nerve)
– vomiting & coughing
Dewax / Syringing the
ear with warm water is
advisable. (cold water–
induce cardiac arrest by
stimulating vagus)
Foreign body ©Dr.N.Mugunthan

13. ©Dr.N.Mugunthan

14. Middle ear or Tympanic cavity
©Dr.N.Mugunthan

15. ©Dr.N.Mugunthan

16. Lateral wall of Middle ear
©Dr.N.Mugunthan

17. Tympanic membrane or ear drum
Definition:
• Oval,semitransparent,pearly
grey trilaminar membrane &
separates the middle ear from
ext.ear
Measurements:
• 9-10mm diameter(max)
• 8-9mm diameter(min)
Position:
• Placed obliquely (55° angle
with floor of ext.acou.meatus)
• Newborn-horizontal
©Dr.N.Mugunthan

18. Tympanic membrane cont…
Peripheral margin of
memb. – fibro
cartilaginous ring
Tympanic sulcus
Tympanic sulcus deficient
above
Ant.& Post.malleolar folds
– attach to lateral process
of malleus
©Dr.N.Mugunthan

19. Subdivisions:
Pars flaccida
Pars tensa
Surfaces:
Lateral surface: concave
Medial surface: convex
(most convex region -Umbo)
Between the fibrous &
mucous layer:
Handle of malleus
Crossed medially – chorda
tympanic nerve
Tympanic membrane cont…
©Dr.N.Mugunthan

20. Structure : Three layer
1. Outer cuticular layer
(keratinised, hairless &
devoid of dermal papillae)
2. Intermediate fibrous layer
(outer radiating & inner
circular fibres)
3. Inner mucous layer
(simple columnar or
squamous)
Tympanic membrane cont…
©Dr.N.Mugunthan

21. Arterial supply:
Deep auricular artery (Max.Art)
Stylomastoid artery (Post.auric)
Anterior tympanic artery (Max.Art)
Venous drainage:
Outer layer – drain into EJV
Inner layer - drain into transverse sinus &
pterygoid plexus
Tympanic membrane cont…
©Dr.N.Mugunthan

22. Tympanic membrane cont…
Nerve supply:
1. Cuticular layer:
a. Auriculotemporal
nerve(upper & anterior part)
b. Auricular branch of vagus
(lower & post.part
2. Mucous layer:
Tympanic plexus
(glossopharyngeal &
sympathetic)
©Dr.N.Mugunthan

23. External examination:
1. Cone of light (antero
inferior quadrant)
2. Handle of malleus
3. Long process of incus
Tympanic membrane cont…
©Dr.N.Mugunthan

24. Applied Anatomy:
Myringotomy – postero
inferior quadrant
Perforation of tympanic
membrane
Tympanoplasty
Tympanic membrane cont…
©Dr.N.Mugunthan

25. Anterior wall (carotid wall)
Upper part – 2 bony canal
separated by bony
partition
1. Canal for tensor tympani
2. Auditory tube (bony
part)
Lower part
Bony carotid canal (ICA &
symp.plexus)
Pierced by superior &
inferior carotico-tympanic
vessels & nerves
©Dr.N.Mugunthan

26. Auditory tube
 Pharyngo-tympanic tube or
Eustachian tube
 Connects middle ear with
nasopharynx
 Trumpet shaped
 4cm long
 2 parts :
1. Bony part
2. Cartilaginous part
©Dr.N.Mugunthan

27. Bony part
 Posterior & lateral 1/3 of
auditory tube
 1.2 cm in length
 Lies in petrous part of
temporal bone
2 ends:
1. Lateral end : opens into
anterior wall of
tympanic cavity
2. Medial end : narrow
(isthmus) – attached
with cartilaginous part
©Dr.N.Mugunthan

28. Incomplete cartilage
tube
Superior & medial wall –
cartilage
Inferior (floor) &lateral
wall – fibrous membrane
2 ends:
1. Apex – attached to bony
part
2. Base – tubal elevation in
the nasopharynx
Cartilaginous part
©Dr.N.Mugunthan

29. Functions
To ensure equal air
pressure on both
sides of tympanic
membrane
Closed (normal)
Opened –
swallowing, yawning
& sneezing (tensor &
levator veli palatini)
©Dr.N.Mugunthan

30. Applied anatomy
Spread of middle air infection (ASOM &
CSOM)
Eustachian catarrh
Tubal block (enlarged tubal tonsil)– retraction
of tympanic membrane
Tmt
1. Nasal decongestants
2. Inflate the tube
©Dr.N.Mugunthan

31. Development of external ear
Development of external
ear:
Mesenchymal
condensations
Hillocks of his (6)
(Auricular hillocks)
©Dr.N.Mugunthan

32. Development of tympanic membrane
Trilaminar structure:
1. Outer cuticular layer –
ectoderm of 1st branchial
cleft
2. Middle fibrous layer –
mesoderm
3. Inner mucous membrane
– endoderm of 1st
pharyngeal pouch
(tubotympanic recess)
©Dr.N.Mugunthan

33. Development of auditory tube
• Endoderm of 1st
pharyngeal pouch
(tubotympanic recess)
©Dr.N.Mugunthan

34. Developmental anomalies of external ear
Anotia (absence of
ear/pinna)
Microtia (small ear)
Melotia (low set ear)
Macrotia (large ear)
©Dr.N.Mugunthan

35. Developmental anomalies of external ear
Anotia (absence of
ear/pinna)
Microtia (small ear)
Melotia (low set ear)
Macrotia (large ear)
©Dr.N.Mugunthan

36. Developmental anomalies of external ear
Anotia (absence of
ear/pinna)
Microtia (small ear)
Melotia (low set ear)
Macrotia (large ear)
©Dr.N.Mugunthan

37. Developmental anomalies of external ear
Anotia (absence of
ear/pinna)
Microtia (small ear)
Melotia (low set ear)
Macrotia (large ear)
©Dr.N.Mugunthan

38. Accessory tragus
©Dr.N.Mugunthan

39. Summary
Parts of ear : External, middle & internal ear.
External ear: auricle & ext. auditory meatus
Tympanic membrane:
Attachments
3 Layers
Structures in the middle layer
Development
Auditory tube:
Parts
Functions
Applied anatomy:©Dr.N.Mugunthan