Middle ear anatomy

1. MIDDLE EAR
B BATCH

2. MIDDLE EAR
Middle ear cleft- middle ear with eustachian tube
,aditus antrum and mastoid air cells.
Lined by mucous membrane and filled with air.
Divided into:-
Epitympanum- lying above the level of pars tensa
Mesotympanum – lying opp to pars tensa
Hypotympanum- lying below the level of pars
tensa.

3. Roof :- formed by thin plate of bone- tegmen tympani-
separates tympanic cavity from middle cranial fossa
Floor :- thin plate of bone which separates tympanic
cavity from jugular bulb.
Anterior wall:- thin plate of bone which separates the
cavity from internal carotid artery.
Has two openings for eustachian tube and tensor
tympani muscle.
WALLS OF MIDDLE EAR

4. Posterior wall :- lies close to mastoid air cells.
Pyramid - bony projection through which tendon of
stapedius appears.
 Aditus – an opening through which middle ear
communicates with antrum.
Facial nerve:-runs behind pyramid
Facial recess:-depression lateral to pyramid
Surgically imp as direct access can be made
through this into middle ear.

5. Medial wall:-
Formed by promontory
 Promontory- a bulge due to basal coil of cochlea
 Oval window- into which foot plate of stapes is fixed
 Round window- covered by secondary tympanic
membrane
 Canal for facial nerve
 Processus cochleariformis- hook like projection where
the tendon of tensor tympani takes a turn.
 Sinus tympani:- deep recess medial to pyramid

6. Lateral wall- formed largely by tympanic membrane, to a
lesser extent by bony wall called scutum

7. MASTOID ANTRUM
Air containing space
Communicates with the middle ear through
additus
Roof- tegmen antri
Marked externally on the surface of mastoid by
suprameatal triangle or Mac Evens triangle

8. ADITUS
Opening through which middle ear
communicates with antrum
MASTOID AND AIR CELL
SYSTEM
Mastoid consists of bony cortex and
honey comb like air cells
3 types

9. 3 types(depending upon development of
air cells)
Cellular – mastoid cells are well
developed
Diploetic – consists of marrow spaces
and few air cells
Sclerotic – no air cells.

10. DEVELOPMENT OF
MASTOID
Develops from squamous and petrous
bones
Petrosquamosal suture may persist as
bony plate-Korner’s septum.
Surgically imp- as it cause difficulty in
locating the antrum.

11. DEPENDING ON THE LOCATION,
MASTOID AIR CELLS ARE DIVIDED
INTO-
Zygomatic cells
Tegmen cells
Perisinus cells
Retrofacial cells
Perilabrinthine cells
Peritubal cells
Tip cells, marginal cells, squamosal cells

13. Malleus :- head, neck, handle, lateral
process, anterior process.
 Head and neck lies in the middle ear
 Lateral process forms nob like projection
on the outer surface of tympanic
membrane and gives attachment to ant
and post malleal folds.
EAR OSSICLES
Incus:- body, short
process, long process to
which attaches head of
stapes.
Stapes :-head, neck, ant and post crura
and a foot plate(which is held in the oval
window by annular ligament)
Ossicles conduct sound energy from
tympanic membrane to oval window

14. TYMPANIC PLEXUS
Lies on the promontory
Formed by tympanic branch of glossopharynge
N and sympathetic fibres from plexus around
the internal carotid artery
Supplies medial surface of tympanic membrane
tympanic cavity , mastoid air cells ,bony
eustachian tube, secretomotor fibres for the
parotid gland.
.

15. INTRATYMPANIC MUSCLES
1. Tensor tympani- attached to neck of
malleus
Tenses the tympanic membrane Supplied
by mandibular nerve
2. Stapedius – attached to neck of stapes
Helps to dampen loud sounds
supplied by facial nerve

16. CHORDA TYMPANI
Branch of facial nerve
Enters the middle ear through posterior
canaliculus
Runs on the medial surface of tympanic
membrane
Carries taste from ant 2/3rd of tongue
Secretory fibres to sublingual and
submaxillary salivary glands.

17. LINING OF MIDDLE EAR CLEFT
Mucous membrane of nasopharynx
continuous with that of middle ear,
aditus , antrum, mastoid air cells.
It wraps middle ear structures like
peritoneum. Thus middle ear contains
only air, all the structures lie outside
the mucous membrane.

18. Eustachian tube lined by ciliated epithelium –
pseudostratified columnar in cartilaginous part and
columnar in bony part.
Tympanic cavity lined by ciliated columnar epithelium in
ant and inferior part and cuboidal in posterior part
Epitympanum & mastoid air cells-flat non ciliated
epithelium.
BLOOD SUPPLY
 2 major arteries
Anterior tympanic branch of maxillary artery-tympanic
membrane
Stylomastoid branch of posterior auricular artery –
middle ear and mastoid air cells.

19. 4 minor vessels
Petrosal branch of middle meningeal artery
Superior tympanic branch of middle meningeal artery
traversing along the canal for tensor tympani muscle
Branch of artery of pterygoid canal runs along the eustaschian
tube
Tympanic branch of internal carotid
Veins drain into pterygoid venous plexus and superior petrosal
sinus

20. LYMPHATIC DRAINAGE
•Middle ear and eustachian tube -
retropharyngeal node & upper jugular nodes
•Pinna - preauricular, postauricular, parotid , infra
auricular, deep jugular & spinal accessory nodes.

21. THANK YOU