Middle ear Middle ear

Middle ear structuresMiddle ear structures

Middle ear Middle ear cavity/tympanucavity/tympanumm

Tympanic Tympanic membranemembrane

Ossicles/Middle Ossicles/Middle ear bonesear bones

Middle ear cavityMiddle ear cavity

Approximately 2 cmApproximately 2 cm3 3 in in volumevolume

Comprised ofComprised of

Tympanic cavity between Tympanic cavity between outer and inner earouter and inner ear

Epitympanic recess Epitympanic recess above the TMabove the TM

Mastoid recess contained Mastoid recess contained in the mastoid region of in the mastoid region of the temporal bonethe temporal bone

Tympanic cavityTympanic cavity

Similar to a box with six Similar to a box with six surfacessurfaces

1.1. LateralLateral wall or membraneous wall or membraneous wall: Formed by TMwall: Formed by TM

2.2. MedialMedial wall or labyrinthine wall or labyrinthine wall: Promontory (outer wall wall: Promontory (outer wall of inner ear)of inner ear)

Contains oval and round Contains oval and round windowswindows

3.3. Anterior wall or carotid wallAnterior wall or carotid wall

4.4. Posterior wall or mastoid wallPosterior wall or mastoid wall

5.5. Inferior wall or jugular wallInferior wall or jugular wall

6.6. Superior wall or tegmental Superior wall or tegmental wallwall

Tympanic membraneTympanic membrane

Located in a bony grooveLocated in a bony groove

Held in place by fibers and cartilageHeld in place by fibers and cartilage

Cone shaped, translucentCone shaped, translucent

55 to 90 mm55 to 90 mm22 in area in area

http://www.ghorayeb.com/AuricleEACAnatomy2.html

Tympanic membrane, cont’d.Tympanic membrane, cont’d.

Composed of two sets of Composed of two sets of fibers: fibers:

1.1. Radiates outward from Radiates outward from centercenter

2.2. Rings of fibersRings of fibers

Two regions in tympanic Two regions in tympanic membrane:membrane:

Superior region: Pars Superior region: Pars flaccidaflaccida

Inferior region: Pars Inferior region: Pars tensatensa

Tympanic membrane, cont’d.Tympanic membrane, cont’d.

Umbo: Region of maximum concavityUmbo: Region of maximum concavity

Tympanic membrane attached to ossicles.Tympanic membrane attached to ossicles.

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/ear.html

Ossicles Ossicles

1.1. Malleus: HammerMalleus: Hammer

2.2. Incus: AnvilIncus: Anvil

3.3. Stapes: Stirrup Stapes: Stirrup http://www.ghorayeb.com/StapesPics.html http://www.ghorayeb.com/StapesPics.html

Head of malleus and body of incus located in Head of malleus and body of incus located in the epitympanic recessthe epitympanic recess

http://oto.wustl.edu/bbears/ossicle.htm http://oto.wustl.edu/bbears/ossicle.htm

http://audilab.bmed.mcgill.ca/~daren/3Dear/mid1.html

MalleusMalleus

HeadHead

Anterior and posterior Anterior and posterior processesprocesses

Handle or ManubriumHandle or Manubrium

IncusIncus

BodyBody

Short Short crus/processcrus/process

Long Long crus/processcrus/process

(Plural of crus: (Plural of crus: Crura)Crura)

StapesStapes

Head or Head or capitulumcapitulum

Two bony cruraTwo bony crura

Flat oval bone Flat oval bone called footplatecalled footplate