Embed Size (px)
Citation preview
1
THE EAR
Major Rahul JhaGraded Specialist
AnatomyACMS
Introduction• Organ of hearing and also plays an important role in
equilibrium.• Divided into three parts:-
– External ear.– Middle ear.– Internal ear.
• External ear consists of Pinna/auricle. • Tympanic membrane at the medial end of EAM.• Middle ear – an air filled space containing ear ossicles.• Communicates with the nasopharynx through auditory tube.• Internal ear consists of bony labyrinth & fluid filled labyrinth.
2
3
THE EAR
EXTERNAL EAR
Components–Pinna–EAM–Concerned with reception of noise.
4
EXTERNAL AUDITORY MEATUS
5
6
EXTERNAL AUDITORY MEATUS• Length: 2.5 cms • Parts
– Cartilagenous : lateral 1/3rd
– Bony: medial 2/3rd
Bends– B/T lat 1/3rd & medial 2/3rd
– 5 mm from TMDirection
– Backwards & medially
• To examine, pull ear.
LAT
MED
7
EAMEpithelium– Adherent to bone & cartilage– Ceruminous glands– Secretions prevent entry of bacteria, make it waterproof
Blood supply– Ant tympanic– Deep auricular– Post auricular
Nerve supplyMedial 1/4:
• IX CN • Auricular br of X CN (Arnold’s)
Lateral 3/4:• Roof: ATN• Floor: Great auricular N
Tympanic membrane
• Thin semi-transparent membrane which forms the partition between the EAM & the middle ear.
• Placed obliquely at an angle of 55 degrees with the floor.
• Faces forward, downward & laterally.
8
TYMPANIC MEMBRANE
11
Angle of TM to EAM
12
TYMPANIC MEMBRANESubdivisions• By malleolar folds
– Pars flaccida (Shrapnel’s membrane)• Present between folds• Lax area
– Pars tensa• Rest of membrane• Tense due to
– Attachment of handle of malleus– Radiating fibres of intermediate layer PF
PT
AMF
PMF
Line of attach of handle of malleuson medial surface
13
TYMPANIC MEMBRANESurfaces
Lateral surface• Concave, directed down, forward & laterally
Medial surface• Convex, max at umbo• Handle of malleus attached here• Chorda tympani is medial to handle of malleus
14
StructureFrom lateral to medial
Outer cuticular layer• Lined by str squamous nonkeratinized epithelium
Intermediate fibrous layer• Outer radiating, inner circular fibres
Inner mucous layer• Lined by columnar epithelium with patchy ciliated
Handle of malleus & chorda tympani lie b/t mucous &intermediate fibrous layer
TYMPANIC MEMBRANE
15
Outer cuticular layer
Middle fibrous layer
Inner mucous layer
Deep circularfibres
SuperficialRadiating fibres
Pars flaccida
TM: STRUCTURE
16
17
Nerve Supply– Lateral surface
– ATN– Vagus N (auricular br)
– Medial surface• IX CN (tympanic br-Jacobson’s N)• Chorda tympani
Blood Supply– Deep auricular br of maxillary (lateral surface)– Ant tympanic Ar– Post auricular: stylomastoid br
TYMPANIC MEMBRANE
18
CLINICAL ANATOMY
• ASOM– Pus discharged laterally
• Myringotomy• Incision at posteroinferior quadrant
–Prevent damage to chorda tympani–Rich blood supply: healing faster
19
AUDITORY OSSICLES
20
MALLEUS• Head
– In epitympanic recess– Post surface: facet for incus-
Incudomalleal jt: Saddle jt• Neck
– against pars flaccida– Chorda tympani cross medial
to neck• Handle
– Project down & back till umbo– processes
• lateral pr : Upper end, handle & lat pr attached to fibrous layer of TM, malleolar folds
• Anterior pr : attachment of ant lig of malleus
21
INCUSBody
• In epitympanic recess• Articulates anteriorly with
head of malleus
Short process• Lig attached to fossa
incudis (post wall of TC)
Long process• Hook medially, articulate
with stapes• Incudostapedial joint: ball
& socket
22
STAPES• Head
– Articulates with lenticular nodule of incus
• Neck– Stapedius attached to back
of neck• Ant & post limbs• Foot plate
– anchored to fenestra vestibuli by annular lig
– syndesmosis
23
MIDDLE EAR
Biconcave box like cavityLocation
– Petrous temporal bone
Parts– Roof– Floor– Walls
• Anterior & Posterior• Medial & Lateral
24
Canal for T T
Auditory tube
Aditus to antrum
Mastoid antrum
Mastoid cells
Mastoid process
EAM
Middle ear (Tympanic cavity)
MIDDLE EARHt & Length: 15 mmMedial & lateral walls: 2 mmRoof: 6 mmFloor: 4 mm
25
Auditory tube
Tegmen tympani Aditus to antrumMastoid antrum
Mastoid air cells
Mastoid process
MiddleEar
ANT & POST WALLS & ROOF
26
Epitympanicrecess
Aditus
Auditory tube
ICA
Sup bulb of IJV
VII CN
ROOF & FLOOR
27
Auditory tube
Cochlea
Semicircular canal
Middle ear
Tympanic antrum
Vestibule
Stapes
Tympanic membraneEAM Internal acoustic meatus
Innerear
LATERAL & MEDIAL WALLS
28
LATERAL & MEDIAL WALLS
29
MEDIAL WALL
30
MIDDLE EAR: COMMUNICATIONS
Anterior wall • auditory tube
Posterior wall• mastoid antrum
Medial wall • inner ear
Lateral wall • tympanic membrane
31
Left ear: TM removed
Roof
Floor
Medial wall
Antwall
Postwall
32
MIDDLE EAR: WALLS & FEATURES
33
Formed by – Tegmen tympani
• Thin bony plate of petrous temporal• Separates tympanic cavity from MCF• Pierced by lesser & greater petrosal nerves
Applied – If unossified: spread of infection to meninges– Venous drainage to superior petrosal sinus through
petrosquamous suture: infection to sinus
ROOF
34
Petrous temporal
ROOF
35
MIDDLE EAR: ROOF
36
FLOORFormed by
– Plate of bone above jugular fossa
Relations– Anterior
• Carotid canal– Posterior
• IJVTympanic canaliculus - tympanic br of IX CN enters
Applied– Spread of infection to IJV: thrombosis
37
Epitympanicrecess
Aditus
Auditory tube
ICA
Sup bulb of IJV
VII CN
MIDDLE EAR: FLOOR
38
ANTERIOR WALL
Shortened by approximation of roof & floorAnteriorly has post wall of carotid canal
Features– Canal for
• Tensor tympani• Auditory tube
– Processus trochleariformis• Bony shelf extends back on medial wall & turns lateral:
provide pulley for tensor tympani to get attached to handle of malleus
39
POSTERIOR WALL
Wider above than belowFeatures
1. Aditus to mastoid antrum• Epitympanic part communicate with mastoid antrum
2. Facial canal: in lower part3. Pyramid
• Projects above facial canal• Contains stapedius, from apex tendon
40
Left ear, TM removed
Roof
Floor
Medial wall
Antwall
Postwall
41
LATERAL WALLComponents
Tympanic MembraneEpitympanic recess
• Part above tympanic cavity– Contains
» Upper half of malleus » Greater part of incus
42
MEDIAL WALLFeatures
1. Promontory• Due to basal turn of cochlea• Tympanic plexus (IX CN)
2. Fenestra vestibuli (fossa ovalis)• Behind & above promontory• Closed by base of stapes & annular ligament
3. Fenestra cochleae (fossa rotunda)• Below & behind promontory• Closed by secondary TM (separate TC from scala tympani)
4. Sinus tympani• Depression behind promontory• Position of ampulla of post semicircular canal
5. Facial canal• Oblique part, run back & down above fenestra vestibuli
6. Processus trochleariformis
43
PosteriorLeft ear, TM removed
roof
floor
Medial wall
Antwall
Postwall
44
MEDIAL WALL
MEDIAL WALL
46
MIDDLE EAR: MUSCLES
47
TENSOR TYMPANI
Origin• Bony & cart part of AT, becomes tendon, hooks around
processus trochleariformis
Insertion• Handle of malleus: upper part
N/S• Nerve to Medial pterygoid
Actions• Pull handle of malleus, TM concave, makes tense• Increase tight adhesion of footplate to fenestra vestibuli
– Hence dampens sound
48
STAPEDIUSOrigin
• Interior of hollow pyramid
Insertion• Back of neck of stapes
N/S• Facial nerve
Actions• Retract neck of stapes from fenestra vestibuli• Paralysis: hyperacusis
49
CLINICAL ANATOMY
1. Otitis media2. Otosclerosis3. Injury to nerve to stapedius
• Hyperacusis
50
Normal TM Wax
CLINICAL ANATOMY
51
Serous otitis mediaASOM
CLINICAL ANATOMY
52
Perforation Tympanosclerosis
CLINICAL ANATOMY
53
PERFORATIONS
54
OTITIS EXTERNA
55
THANK YOU
