Middle Ear Flashcards
What is the TM?
A dividing wall
Not a part of outer or middle ear.. Technically both
One boundary of middle ear
Cone shaped - concave
TM held in place by..
Fibers and cartilage
Main portion of middle ear..
Between TM and promontory
Middle ear cavity
2cc’s volume
Contains smaller upper cavity - epitympanic recess
Connected to nasopharynx by Eustachian tube
Three bones: malleus, incus, stapes
3 layers of TM
Outer - same skin as bony portion of canal
Middle - (most imp) contains radial and circular fibres
Inner - lined w mucous membrane
Pars flacida
Sparse area near the top of TM
Lots of lesions can happen there
Umbo
Region of max concavity of TM
Malleus
Bone that connects to the TM
Most lateral of the three ossicles
This is what pulls back the eardrum
Forms the cone of light (if drum not healthy, won’t have this)
Head connects to incus and extends into epitympanic recess
Incus
Middle ossicle
Connects to malleus and stapes
Stapes
Connects to incus
Footplate connects to oval window
Muscles of the middle ear
Tensor tympani
Stapedius
Sound travels thru ME in 3 ways
- bone conduction
- air in middle ear cavity
- ossicular chain - most effective - vibrates oval window
Inner ear filled with…
Fluid
Impedance mismatch
Sound moves from air to fluid going from outer to middle ear, so we need a lot more pressure to move the sound effectively
- it’s hard to move anything in a substance thicker than air
2 ways our MEs compensate for the impedance mismatch
- Area differential (impedance matching)
2. lever action
