1 - Anatomy & Physiology of Middle Ear Flashcards
The Eustachian tube connects the middle ear with the __________.
Nasopharynx
What is the middle ear filled with?
Air
What is the largest part of the tympanic membrane?
The pars tensa
How many parts does the pars tensa have?
3
Describe the pars tensa
4
Tense
Vibrates in response to sound
Has a blood supply
Is innervated
What is the densest part of the tympanic membrane?
Pars flaccida
Which is less tense: the pars tensa or the pars flaccida?
The pars flaccida
What is the function of the tympanic membrane?
To transduce sound pressure into mechanical vibrations
Name the three ossicles
Malleus
Incus
Stapes
What is the extension of the malleus that connects to the tympanic membrane?
Manubrium
What is the name of the center of the tympanic membrane where the Manubrium attaches?
Umbo
What does the head of the malleus connect to?
The head of the incus
What are the two middle ear muscles?
Stapedius muscle
Tensor Tympani
What is the smallest human muscle?
Stapedius muscle
Where does the stapedius muscle attach?
Attaches to the head of the stapes
Where does the tensor tympani muscle attach?
To the upper part of the manubrium
To what does the tensor tympani muscle run parallel to?
The Eustachian Tube
What is unique about the middle ear muscles?
The are totally encased in bone.
Only their tendons are exposed to attach to the ossicles
What is the function of the middle ear muscles?
Act in concert to modify the ossicles’ alignment
Provide protection from loud sounds
Provide amplification for soft sounds
What happens to the middle ear muscles during sustained long sounds?
They tense up so that less pressure is being applied to the oval window
What is the dynamic range of hearing?
From the threshold of hearing (softest sound you can detect) to the threshold of pain (loudest sound you can comfortably tolerate)
How is the impedance imbalance of the inner ear compensated for?
The size of the tympanic membrane vs. the size of the stapedial footplate
The leverage created by the geographic configuration of the ossicles
The area of the tympanic membrane vs. the area of the stapedial footplate improves sound transmission by ___________.
25 dB
The leverage provided by the ossicles improves sound transmission by __________.
12-13 dB
What are the four quadrants of the tympanic membrane?
Posterior Superior
Posterior Inferior
Anterior Superior
Anterior Inferior
What are the parts of the middle ear?
5
Tympanic Membrane
Ossicular Chain
Tendons
Muscles
Eustachian Tube
What is the name of the groove where the TM is located?
Tympanic Sulcus
What are the parts of the tympanic membrane?
7
Pars Flaccida
Pars Tensa
Umbo
Cone of Light
Tympanic Ring
Manubrium
Notch of Rivinus
The ear drums slant towards _________.
The nose
What are the three layers of the tympanic membrane?
Cutaneous
Fibrous
Internal
What is the Cutaneous Layer of the TM like?
Outer Layer
Composed of same skin that covers last portion of the external ear canal
What is the Fibrous Layer of the TM like?
It provides most of the structure, integrity, and compliance
Its density is greatest at the center
What are the two layers of the TM’s Fibrous Layer
Radial Fibers
Spiral (Circular) Fibers
What is the Internal Layer of the TM like?
A mucous membrane
What is the Promontory?
A bony area that is the entrance to the cochlea
What holds the ossicular chain in place?
3
Tympanic Membrane
6 Ligaments
Tendons of Tensor Tympani & Stapedius Muscles
What’s different about the middle ear tendons?
They are more elastic than other tendons in body
They produce slower muscle contractions - no sudden contractions
When does the Tensor Tympani muscle move?
During swallowing, chewing, and other facial movements
When does the Stapedius muscle move?
During loud sounds or right before speaking
Its movement is involuntary
What is the difference between the tensor tympani muscle and the stapedius muscle?
Tensor Tympani = Bigger muscle, smaller effect
Stapedius = Smaller muscle, bigger effect
How do the tensor tympani muscle and the stapedius muscle interact together?
The contract in opposite directions to prevent rotation of the ossicular chain
What is the function of the tensor tympani muscle and the stapedius muscle?
To modify the vibration of the ossicular chain
What are the six ligaments of the middle ear?
Superior malleal ligament
Lateral malleal ligament
Anterior malleal ligament
Superior Incudal Ligament
Posterior incudal ligament
Annular Ligament
What are the two muscles of the Eustachian Tube?
Tensor Veli Palatini (TVP)
Levator Veli Palatini (LVP)
What is the function of the Eustachian Tube?
To equalize the air pressure in the middle ear with the air pressure of the environment
To allow fluids in the middle ear to be drained
What is the function of the middle ear?
To compensate for the impedance mismatch between the outer and inner ears
It takes more energy to produce a sound wave in the inner ear fluids than the atmosphere where the sound was generated
What is impedance?
The sum of all the energy that opposes the transmission of sound
How much larger is the TM than the Oval Window?
15x larger
What is a conductive loss of hearing?
When a patient is missing or has malfunctioning TM and/or ossicles
When the Eustachian Tube’s muscles are relaxed, the lumen is?
Closed
When the Eustachian Tube’s muscles are contracted, the lumen is?
Open
What is the Lumen?
The tube part of the Eustachian Tube
What hair cells are usually damaged in noise-induced hearing loss?
The outer hair cells