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Middle ear Middle ear structures Middle ear cavity/tympanum Tympanic membrane Ossicles/Middle ear bones Middle ear cavity Approximately 2 cm3 in volume Comprised of Tympanic cavity between outer and inner ear Epitympanic recess above the TM Mastoid recess contained in the mastoid region of the temporal bone Tympanic cavity Similar to a box with six surfaces 1. Lateral wall or membraneous 2. Medial wall or labyrinthine wall: 3. Anterior wall or carotid wall 4. Posterior wall or mastoid wall 5. Inferior wall or jugular wall 6. Superior wall or tegmental wall wall: Formed by TM Promontory (outer wall of inner ear) Contains oval and round windows Tympanic membrane Located in a bony groove Held in place by fibers and cartilage Cone shaped, translucent 55 to 90 mm2 in area http://www.ghorayeb.com/AuricleEACAnatomy2.html Tympanic membrane, cont’d. Composed of two sets of fibers: 1. Radiates outward from center 2. Rings of fibers Two regions in tympanic membrane: Superior region: Pars flaccida Inferior region: Pars tensa Tympanic membrane, cont’d. Umbo: Region of maximum concavity Tympanic membrane attached to ossicles. http://hyperphysics.phy-astr.gsu.edu/hbase/sound/ear.html Ossicles 1. Malleus: Hammer 2. Incus: Anvil 3. Stapes: Stirrup Head of malleus and body of incus located in the epitympanic recess http://oto.wustl.edu/bbears/ossicle.htm http://www.ghorayeb.com/StapesPics.html http://audilab.bmed.mcgill.ca/~daren/3Dear/mid1.html Malleus Head Anterior and posterior processes Handle or Manubrium Incus Body Short crus/process Long crus/process (Plural of crus: Crura) Stapes Head or capitulum Two bony crura Flat oval bone called footplate