Middle Ear Review Flashcards
Where does the eustachian tube drain to?
posterior aspect of Inferior turbinate
muscles that help open and close the eustachian tube
tensor veli palatini, levator veli palatini, salpingopharyngeus, and tensor tympani
in an airplane, our ET will ___
suction the nasopharynx secretions into the ME space
when scuba diving or experiencing negative ME pressure, our ET will __
lock and collect fluids in the ME
term for an abnormal ET that doesn’t close?
patulous (causes feelings of fullness and resounding voice)
total amount of amplification (in dB) from impedance matching?
33-34 dB
how to measure the MEMR?
immitance testing (decays, tymps, reflexes)
the MEMR requires 3 things to happen:
- normal ME mechanics and normal TM movement
- a loud sound (75-85 dB)
- neural synchrony and a good reflex arc
what is the opening to the mastoid antrum called?
mastoid aditus
3 sections of middle ear
epitympani, mesotympani, hypotympani
2 portions of the eustachian tube:
2 portions of the eustachian tube:
narrowest portion of the eustachian tube:
isthmus
Bony portion of the eustachian tube
widest at tympanic end, always open
when does the fibrocartilaginous portion of the eustachian tube open?
swallowing, yawning, forceful inflation (normally at rest)
the ET in kids is _____
half the size of the adult, more horizontal
at the nasopharynx opening, what lines the ET?
respiratory epithelium (it’s a mucous membrane)
functions of the ET
ventilate, drain, and protect the middle ear space
why is the ET closed most of the time?
to protect the ME from sudden loud sounds
how can we release the “lock” of the ET?
valsalva maneuver (plug nose and blow), or politzerization (balloon release)
the 3 ME ossicles
malleus, incus, stapes
parts of the malleus
articulatory facet for incus, head, neck, lateral and anterior processes, manubrium, umbo
parts of the incus
short crus, body, long crus, lenticular process, facet for malleus
parts of the stapes
head, neck, anterior crus, posterior crus, footplate
ligaments of the malleus
anterior mallear, lateral mallear, superior mallear
ligaments of the incus
superior incudal, posterior incudal
ligaments of the stapes
stapedius annular
tendons of the middle ear ossicles
tensor tympani
stapedius muscle
nerve in the ME space
chorda tympani
3 impedance matching mechanisms
area ratio, lever action, buckling effect
biggest contributor to impedance matching
area difference between TM and stapes footplate
what are two or 3 functions of ET?
pressure air equalization
fluid drainage
protection from sounds and fluids getting into it
what happens if we don’t have impedance matching?
99% of the energy would bounce back out!
what is the primary reason for the acoustic reflex?
to protect us from our own voice
the MEMR happens in ______ ear(s)
both, simultaneously
the stapedius muscle is innervated by the _____
cn vii (facial nerve)
Which cranial nerve provides the main motor input for the the acoustic reflex (also referred to as the stapedial reflex)?
CN VII
Cranial nerve VI is called the
the abducens
What factor provides the largest contribution the the impedance matching function served by the the middle ear so that sound energy can be converted from acoustic waves to mechanical vibration and then hydraulic/fluid movement in the cochlear without the loss of most of the sound energy?
area size difference
What is the location of the primary motor cortex (M1) on the cerebrum?
precentral gyrus
What structure/s are located in the hypotympanum?
Opening of the Eustachian tube in the middle ear
Which of the following is NOT a function of the Eustachian tube?
ventilation of the middle ear
drainage of middle ear secretions
protection from excessive nasopharyngeal sounds and secretions
To remain open at all times to improve auditory resonances
remaining open at all times
What are the acoustic reflex 4 neuron reflex arc?
CN VIII to the ipsilateral anteroventral cochlear nucleus, then to the medial superior olive, then to the facial motor nucleus, then down CN VII to the stapedius muscle
What is the neurotransmitter in muscle neurons?
Acetecholine
Posterior wall
mastoid wall
Short ipsilateral pathway
sound –> (CN VIII) cochlea –> anteroventral cochlear nuclei –> facial motor nerve –> (CN VII) stapedius
Long Ipsilateral pathway
sound –> (CN VIII) cochlea –> anteroventral cochlear nuclei –> medial superior olive –> facial motor nerve –> (CN VII) stapedius
short contralateral pathway
cochlea –> (CN VIII) anteroventral cochlear nuclei –> CROSS MIDLINE –> medial superior olive –> facial motor nerve –> (CN VII) stapedius
Long contralateral pathway
cochlea –> anteroventral cochlear nuclei –> medial superior olive –> CROSS MIDLINE –> facial motor nerve –> stapedius
dB boost from area difference of IMM
25-26 dB gain
dB boost from lever action of IMM
2 dB gain
dB boost from TM buckling
about 6 dB gain
How do we get mastoiditis?
middle ear gets infected, aditus opens into the mastoid creating a route to get through that inlet to the mastoid antrum back where air cell pockets are of the mastoid - this area is prone to getting infected
Epitympanum includes:
top of ossicles and aditus to mastoid antrum
mesotympanum includes:
promontory
Hypotympanum includes:
jugular and ET
Explain the ET of adults
about 36 mm and directed downward forward and medially from the middle ear
Where is ET narrowest and widest?
ET is widest at tympanic end and passes through squamous and petrous portion of temporal bone
narrows closer to isthmus
How long is ET in infants?
18 mm
Where in ET and what type of tissue is lining middle ear?
mucous membranes (natural to have fluid here due to this)
At its nasopharyngeal opening, the eustachian tube is lined by respiratory epithelium
What are the two portions of ET?
lateral third bony portion (12mm) arising from anterior wall of tympanic cavity
medial two thirds (24mm) fibrocartilagenous portion entering nasopharynx
Why do infants get more ear infections?
shorter passageway, horizontal feature and lack of gravity helping to drain
What are the physiologic functions of the eustachian tube?
Ventilation of the middle ear,
drainage of middle ear secretions, and
protection from excessive nasopharyngeal sounds and secretions
What muscle opens the ET when yawning or swallowing?
tensor veli palatini
What else contributes to otitis media in children?
repeated upper respiratory tract infections
enlarged adenoids
ET function is impaired by the presence of ______
cleft palate
Maintained middle ear pressure? (+ and -)
+50 -50
the mucous membrane takes in what to do work?
air (1 mL absorbed in 24 hrs)
What works as a gas reservoir for the middle ear?
mastoid cell system
How does the ET protect when closed at rest?
Sudden loud sounds do not reach the middle ear through the nasopharynx and thus do not cause tympanic membrane perforation
How does the ET drain normal secretions?
by the mucociliary transport system and by repeated active tubal opening and closing, which allows secretions to drain into the nasopharynx
What can cause Otorrhea
An abnormlaity in the closed middle ear system, such as tympanic membrane perforation or after mastoid surgery, sometimes results in reflux of nasopharyngeal secretions into the tube
What creates high middle ear pressure, which leads to suction of nasopharyngeal secretions into the middle ear?
diving or ascending in airplane or forceful nose blowing
What type of pressure causes locking of the ET?
negative pressure (diving, flying etc.)
How can we unlock or resolve neg. pressure in middle ear?
Inflation of the eustachian tube by Valsalva maneuver or by politzerization breaks the negative pressure in the middle ear and clears the effusion.
Patulous ET
When the ET is abnormally patent (open), and the patient’s own voice resounds into his or her ear (occlusion effect) with a feeling of fullness in the ear.
What type of energy is air in outer ear?
Acoustic
What type of energy is transformed by the TM?
mechanical
What type of energy does stapes footplate push into in oval window?
hydromechanical
Why do we want the ability to tighten the muscles in our middle ear?
protecting from loud sounds by muffeling (not from loud instantaneous sounds; pulls after the loud noise has already happened)
create our vocalizations when we talk, sneeze, laugh, etc coming from trachea and is around 100 db in our head; before we start to vocalize it tightens our muscles and ossicles so we don’t overbear ourselves and blow our own ears out (protect from own localizations)
attenuating lower frequencies (attenuate back ground noise so we can hear speech sounds for speech in background noise)
How much gain increase do we see from middle ear IMM?
33-34 dB
Are the MEMR concomitant?
yes they happen at the same time
Does MEMR need conscious cortical thought to react?
no, mediated at the brainstem level (subcortical)
What are the 3 pre-existing requirements MEMR needs?
Normal middle ear mechanics
A “loud sound” ….75-85 dB SPL
An intact reflex arc and GOOD NEURAL SYNCHRONY (sodium potassium movement in cells in nerve fibers)
Which innervation Enters at the cerebellopontine angle on brainstem of the reflex arc?
cochlear nucleus
why do we have 2 ears with 2 systems?
brainstem and brain compare sounds from L and R ears to:
helps localize, hear in noise
what’s happening on both sides of the head so we know where we are in space
When discussing anatomic location, peripheral refers to what and central refers to what?
peripheral: away from midline, outside of bony protection of meninges
central: towards midline, inside CNS cranial vault and vertebral column
Is CN VII in the CNS?
No it is PNS because it is at the brainstem and outside of CNS
Are the cochlear and vestibular nucleus in the CNS?
yes
Describe the MEMR.
primary muscle is stapedius
protects from loud exposure by tightening ossicles, reduces low pitches to hear in noise, protects from own localizations
