11. Lateral wall
▶ Largely by tympanic membrane
▶ Lesser extend by bony outer attic wall (SCUTUM)
▶ Chorda tympani nerve passes across-lateral to long
process of incus & medial to handle of malleus.
13. Roof of middle ear
▶ Formed by Tegmen tympani(both petrous and
squamous portion of temporal bone form it)
▶ Separates tympanic cavity from middle cranial fossa.
▶ Also forms roof of aditus and antrum.
14.
15. Floor of the middle ear
▶Formed by thin plate of bone separates
the hypotympanum from the dome of
jugular bulb.
▶Maybe congenitally deficient - jugular
bulb is separated by mucosa.
▶Tympanic branch of glossopharyngeal
nerve pierces floor between jugular fossa
and lower opening of carotid canal.
21. Posterior wall of middle ear
▶ Pyramid-bony projection; stapedius tendon
appears through its submit, gets attached to neck
of stapes.
▶ Aditus-opening through which attic
communicates with the antrum.
▶ Fossa incudus-close to aditus, lodges short
process of incus.
▶ Vertical part of facial canal behind pyramid.
▶ Posterior canaliculus- aperture for emergence of
chorda tympani.
22.
23. Facial recess
▶ Depression on posterior wall, lateral to pyramid.
▶ Shallow lower down
▶ Medially - facial nerve
▶ Laterally – chorda tympani
▶ Above – fossa incudis
▶ Posterior tympanotomy-direct access to middle ear
without disturbing posterior wall.
26. Ossicles- malleus
▶Largest
▶ Parts-head, neck, handle, lateral and anterior processes.
▶Head and neck in epitympanum.
▶ Handle in fibrous layer of tympanic membrane.
▶Suspended by superior malleal ligament
▶ Lateral process receives ant and post folds from
tympanic annulus
▶ Articulates with the incus-a saddle type synovial joint
27. Incus
▶ Body
▶ Two processes
▶ Short process
▶Long process(parallel to handle of
malleus)
▶ Lenticular process- articulate with
head of stapes.
29. Mastoid antrum
▶ Large air containing space
▶ Communicates with attic through aditus
▶ Roof-tegmen antri (cont. of tegmen tympani)
▶ Lateral part formed by plate of bone marked by
McEwen’s triangle.
▶ Floor – openings of mastoid air cells.
30.
31. Mastoid & its air cell system
▶ Mastoid consists of bone cortex and air cells.
▶ Develops from squamous & petrous bones
▶ Petrosquamal suture persists as bony plate
korner’s septum, separating superficial
squamosal and deep petrosal cells
▶ 3 types of mastoid:
▶ Well-pneumatised or cellular-well developed cells
with thin intervening septa.
▶ Diploetic- mastoid with marrow spaces & few air cells.
▶ Sclerotic or acellular- no cells/marrow spaces.
32. Depending on location, mastoid cells are divided:
▶ Zygomatic
▶ Tegmen
▶ Perisinus
▶ Retrofacial
▶ Perilabyrinthine
▶ Peritubal
▶ Tip
▶ Marginal
▶ Squamosal
33. Intratympanic muscles
▶ Tensor tympani
▶ Origin-cartilaginous part of auditory tube
▶ Insertion- upper end of handle of malleus
▶ Nerve supply by- mandibular nerve
▶ Action- tenses tympanic membrane
▶ Stapedius
▶ O-pyramidal eminence
▶ I-neck of stapes
▶ N-facial n.
▶ A-tilts its footplate in oval window
34. Blood supply
6 ARTERIES
▶ Anterior tympanic branch of maxillary a.- tympanic
membrane.
▶ Stylomastoid branch of posterior auricular a.- middle ear
& mastoid cells
▶ Petrosal branch of middle meningeal a.
▶ Superior tympanic branch of middle meningeal a.
▶ Tympanic branch of internal carotid
▶ Branch of a. of pterygoid canal.
Venous drainage: pterygoid venous plexus & superior
petrosal.
36. Nerve supply
▶ Tympanic branch of glossopharyngeal n.-sensory to
lining of middle ear, antrum & auditory tube.
▶ Superior & inferior carotico-tympanic n.- vasomotor
▶ Facial n.-
▶ Chorda tympani-taste sensation & secretomotor fibres
for submandibular & sublingual glands
▶ Greater petrosal n.-secretomotor lacrimal, nasal glands
▶ N. to stapedius muscle
▶ Mandibular n.
37. Tympanic plexus
▶ nerves
▶ Tympanic branch of glossopharyngeal n.
▶ Superior & inferior carotico-tympanic n.
▶ Branch from Facial ganglion
▶ Supplies mucous membrane of middle ear, mastoid air
cells & Eustachian tube.
38. clinical
▶ Otitis media- common in infants and children.
▶ Progression of URTI to middle ear through
pharyngotympanic tube
▶ Complication:
▶ acute mastoiditis & mastoid abscess
▶ Meningitis & temporal lobe abscess
▶ Labyrinthitis- causing vertigo and vomiting
▶ Cerebellar abscess
39. ▶ Hyperacusis – paralysis of stapedius muscle
▶ Otosclerosis- abnormal ossification of annular
ligament. (m/c cause of conductive deafness in adults)
43. Promontory
▶ Formed by basal turn of cochlea
▶ Contains nerves forming tympanic plexus
▶ Tympanic branch of ninth nerve may be covered by
bone forming a small canal
44. Oval window
▶ Behind and above the promontory.
▶ Connects tympanic cavity with the vestibule.
▶ Closed by footplate of stapes and annular ligament.
45. Round window
▶ Lies below and behind the promontory.
▶ Separates middle ear from Scala tympani.
▶ Closed by fibrous secondary tympanic membrane.
▶ Sinus tympani is a deep recess bounded by subiculum
below & ponticulus above lying between round & oval
window.
