anatomy of middle dear

1. Anatomy of Middle ear
Dr. Suresh Managutti

2. Ear

3. Middle ear (Tympanic cavity)
• Location- petrous part of temporal bone
• Filled with air
• Lined by mucous membrane
• Full adult size at birth
• Communications- in front with lateral wall of
nasopharynx – auditory tube
• Behind with mastoid antrum through aditus to
antrum

4. Communications of middle ear

5. Pistol

6. Measurements
• Vertical diameter- 15 mm
• AP diameter- 15 mm
• TD- 6mm at roof, 2 mm middle, 4mm at floor

7. Subdivisions of middle ear
• Epitympanum (head of malleus, body & short
process of incus)
• Mesotympanum (handle of malleus, long
process of incus and stapes)
• Hypotympanum

8. Distance between medial and lateral
wall

9. Boundaries of tympanic cavity –
(cuboidal- 6 walls)
• Roof –tegmen tympani , greater & lesser petrosal nerves
• Floor- jugular fossa –IJV , tympanic branch of IX N
• Anterior wall- lower part- ICA & sympathetic plexus-
carotico tympanic nerves; upper part- canal for tensor
tympani & auditory tube
• Posterior wall- aditus to mastoid antrum, fossa incudis ,
vertical bony canal for facial nerve , pyramid- stapedius
tendon
• Medial wall- promontory, fenestra vestibuli( oval window)-
stapes, fenestra cochleae (round window) -scala tympani,
sinus tympani- ampulla of P semicircular canal, oblique part
of facial nerve canal, processus trochleariformis
• Lateral wall – tympanic membrane – umbo, pars tensa,
pars flaccida anterior canaliculus for chorda tympani N

10. Structures in the walls of Middle ear

11. Medial view of middle ear

12. Lateral wall of middle ear

13. Facial nerve relations

14. Facial nerve relation to middle ear

15. Tympanic membrane
• Ear drum
• Oval, semitransparent, pearly grey, trilaminar
membrane
• Derived from all 3 germ layers
• 8-10 mm diameter
• Obliquely placed, angle of 55 degrees with floor
of external acoustic meatus
• New born- horizontal ( child withstand noisy
sound better than adult)

16. Tympanic membrane

18. Contents of middle ear
• Ear ossicles – MIS (3)
• Muscles- Tensor Tympani, Stapedius (2)
• Arteries of middle ear(6)
Stylomastoid branch of posterior auricular artery,
anterior tympanic branch of maxillary artery,
petrosal branch of middle meningeal artery,
superior tympanic branch of middle meningeal
artery, branches from ascending pharyngeal artery,
branches from artery of pterygoid canal, tympanic
branches of ICA

19. • Nerves (4)- superior & inferior carotico
tympanic nerves (sympathetic), Chorda
tympani nerve, tympanic branch of
glossopharyngeal nerve (tympanic plexus),
facial nerve- with its 3 branches

20. Ear ossicles

21. Ear ossicles

22. Muscles

23. Layers &Fibres of tympanic membrane

24. Movements of ear ossicles

25. Applied anatomy
• Otitis media- ASOM, CSOM- complications
• Otosclerosis - stapedectomy
• Hyperacusis
• Tympanic membrane perforation
• Myringotomy, Myringoplasty, Tympanoplasty
• Facial nerve & chorda tympani injury
• Eustachian catarrh

26. Otoscopy

27. Stapedectomy & prosthesis