1.2-3 Middle Ear and Eustachian Tube Flashcards
Which cranial nerve passes through the middle ear?
Cranial Nerve 7 Facial Nerve
What is the name of the entrance of the mastoid antrum (air cells)?
Aditus Antrum
State the 5 functional outline of the middle ear in sound conduction:
Vibration of tympanic membrane
Vibration of the bone chain
Amplification of sound by middle ear by 3 mechanism
Frequency responses of the middle ear
Feedback control
True or False: The vibration of eardrum and oval window is even.
FALSE: UNEVEN
True or False: Eardrum vibration is larger on its inferior part
TRUE
What is the total gain provided by the area function of impedance matching?
25 dB
What is the total gain provided by the Lever Function of impedance matching?
2.5 dB
What is the total gain provided by the buckling membrane are of impedance matching?
6 dB gain
What are the two muscles in the middle ear?
Stapedius Muscle and Tensor Tympani
The tensor tympani is attached to the ?
Manubrium
Which is largest the stapedius or the tensor tympani?
Tensor Tympani
In which direction does the tensor tympani pull the TM?
medially
In which direction does the stapedius muscle pull the TM
and stapes?
laterally
Where is the stapedius muscle attached to?
Attached to the head of stapes
The stapedius muscle is smaller or larger than the tensor tympani?
smaller
Stapedius muscles pull the head of the Stapes to rotate _________, and _________
Stapedius muscles pull the head of Stapes to rotate posteriorly, and laterally
What is the relationship between ME muscles and acoustic reflex? (2)
Contraction evoked by loud sound
Increases the stiffness of the ME bone chain
True or False: In humans, stapedius muscle play greater role in AR than tensor tympani m.
TRUE!
Describe the ME impedance test (4):
Is done in external ear canal
Non invasive
Best way to measure AR in clinics
But can’t tell the source of AR (Stapedius vs. TT)`
What are the 3 possible role of the eustachian tube?
1) Balancing air pressure
2) Pathway for cleaning debris through mucociliary transportation
3) Protection against infection from nasal cavity and from loud sound of own voice
How long is the ET in adults?
Approximately 35-38 mm
Is it in infants or adults that the ET is more horizontal?
Infants
Was is the ratio of bone vs. cartilage in the ET?
First 1/3 nearest the middle ear is surrounded by bone, the remaining 2/3 is surrounded by cartilage
What is the name of the meeting point of bone and cartilage in the ET?
Isthmus
Which organs in the mouth are close to the ET and involved in infection? (2)
Tonsil and Adenoids
Protection against infection from nasal cavity and from loud sound of own voice is dependent on…
on proper closing of ET
Pathway for cleaning debris through mucociliary transportation from the ET dependent on…
ET open
Balancing air pressure of the ET is dependent on…
proper opening of ET
At rest, the ET is normally…
closed
Which muscle in the soft palate needs to be activated for cartilage to uncurl and the ET to open?
Tensor Palatini
What actions can cause the tensor palatini activate?
Yawning and Swallowing
What can happen if the ET fails to open properly?
Build up of negative pressure in ME
When do we need air balancing via ET? (2)
Environmental changes: external air pressure change.
Metabolic reason: if ET does not open for long time, negative pressure will build up in ME.
How many minutes a day does the ET open approximately?
3-4 min/day
What can occur with the pars flaccida if there is negative pressure in the ME?
Pars flaccida can distort because of its higher flexibility
What can we insert in the ME through the TM to balance air pressure?
Pressure Equalizing Tube
True or False: When air pressure is BALANCED, the ET can be OPEN more easily, thereby allowing the waste to move out
True
True or False: ET is opened most of the time?
False it’s closed
True or False: ET closing is passively maintained?
True
True or False: Closing can be interrupted by pathology
True
True or False: SHORT-TERM opening causes problems of ME.
FALSE long-term
How would you describe the location of the ET relative to the ME?
The ET runs from anterior wall of ME to posterior wall of nasopharynx
What condition occurs as a result of negative pressure?
Accute Otitis Media
True or False: Pressure Equalizing Tubes eventually fall out on their own.
True
For membrane buckling, where does the tympanic membrane curve?
TM curves from its edges to its attachment at the manubrium.
What is meant by middle ear transfer function?
Shows the gain through the middle ear across frequencies
For the lever mechanism, greater distance = _________ force
smaller force
For the lever mechanism,
smaller distance = _________ force
greater force
What is the total gain of the 3 ME actions and their start and end point?
33.5 dB from the TM to the oval window
What does the MEMR stands for ?
Middle Ear Muscle Reflex
