Anatomy of middle ear

1. ANATOMY OF THE
MIDDLE EAR
GAYATHRI K

2. MIDDLE EAR
• Middle ear is a air filled cavity lies within the temporal bone
• The main function of the middle ear is to transmit vibrations from the tympanic
membrane to the inner ear via the auditory ossicles
• Middle ear is shaped like a cube

3. • Measurements
vertical diameter : 15 mm
anteroposterior diameter : 15 mm
transverse diameter
a)at roof : 6 mm
b)in the centre : 2 mm
c)at the floor : 4 mm
• Communication
anteriorly : with nasopharynx
posteriorly : with mastoid antrum and mastoid air cells

4. CONTENTS
Inside the mucous lining
• Air
Outside the mucous lining
• 3 small bones called ear ossicles : malleus, incus and stapes
• 2 muscles : tensor tympani and stapedius
• 2 nerves : chorda tympani and tympanic plexus
• Vessels supplying and draining the middle ear
• Ligaments of the ear ossicles

5. SUBDIVISIONS OF THE MIDDLE EAR
The tympanic cavity extends much beyond the limits of tympanic membrane,
It is divided into 3 parts, namely
• Epitympanum
• Mesotympanum
• Hypotympanum

6. BOUNDARIES
• Roof
Formed by tegmen tympani
seperates tympanic cavity
extend posteriorly to form roof of aditus and antrum
• Floor
Formed by thin plate of bone
seperates tympanic cavity from jugular bulb
tympanic branch of glossopharyngeal nerve pierces the floor between jugular fossa and lower
opening

7. • Anterior wall
thin plate of bone
separate the cavity from internal carotid artery
has two opening – a) upper one for the canal tensor tympani muscle
b) lower one for the eustachian tube
• Posterior wall
separate the tympanic cavity from mastoid antrum and mastoid air cells
it has the features like – aditus ad antrum, fossa incudes, pyramid, vertical part of facial canal and
posterior canaliculus for chorda tympani

9. • Medial wall
separate the tympanic cavity from internal ear
medial wall presents – promontory, oval window, round window, sinus tympani,
prominence of oblique part of the facial canal, prominence of lateral semicircular canal of
the internal ear
• Lateral wall
formed by tympanic membrane
separate the tympanic cavity from the external auditory meatus

10. EAR OSSICLES
• Malleus
resemble hammer
has head, neck, handle, lateral process
and anterior process
muscle attached – tensor tympani
• Incus
anvil
consists of large body and 2 process – long and short process

11. • Stapes
stirrup
consists of head, neck, anterior and
posterior crura and footplate
• INTRATYMPANIC MUSCLES
tensor tympani and stapedius

12. ARTERIAL SUPPLY
• Anterior tympanic branch of maxillary artery
• Stylomastoid branch of the posterior auricular artery
• Petrosal branch of the middle meningeal artery
• Superior tympanic branch of the middle meningeal artery
• Artery of pterygoid canal
• Tympanic branch of internal carotid artery

13. VENOUS DRAINAGE
• Pterygoid venous plexus
• Superior petrosal sinus
LYMPHATIC DRAINAGE
• Retropharyngeal lymph node
• Parotid lymph node
• Upper deep cervical lymph node

14. NERVE SUPPLY
• Tymapanic branch of glossopharyngeal nerve
• Superior and inferior caroticotympanic nerves
• Facial nerve
• Mandibular nerve
TYMPANIC PLEXUS
It is a plexus of nerves on the promontory in the medial wall of the middle ear.
It is formed by
tympanic branch of the glossopharyngeal nerve
superior and inferior caroticotympanic nerves
branch from facial ganglion

15. MASTOID ANTRUM
It is a large air containing space in the upper part of the mastoid process
DEVELOPMENT OF THE MIDDLE EAR
develop from endodermal tubotympanic recess
malleus and incus develop from mesoderm of first arch
stapes develop from mesoderm of second arch

16. CLINICAL CORRELATION
• Infection of the middle ear (otitis media)
common in infant and children
infective agents reach the middle ear
from upper respiratory tract
long standing infection leads to
chronic suppurative otitis media (CSOM)
• Hyperacusis
abnormally increased power of hearing
• Otosclerosis
impedes the movements of stapes and causes deafness

17. THANKYOU