Chapter 9: The Middle Ear Flashcards
Purpose of the Eustachian Tube
Equalize the pressure in the middle ear to the outside world
Mastoid Bone
-Honeycomb bones of the skull that surround the middle ear
-Place where bc vibrator is placed
Oval Window
-Upper window connecting the middle ear space to the inner ear
Round Window
-Lower window covered by a thin, strong elastic membrane
Promontory Window
-Bony portion of the cochlea that extends into the middle ear space. Separates the oval and round windows
Function of the Ossicles
-To carry tympanic membrane vibrations to the inner ear
-Lever action of the ossicular chain adds to signal intensity to overcome the impedance mismatch of the middle and inner ear
Impedance Matching
-Ossicular chain and size difference between the TM and oval window achieve this
-Helps sound travel through air to fluid in the inner ear without the sound being reflected/loss.
Stapedius and Tensor Tympani Muscles
-In the middle ear and contract to loud sounds (acoustic reflex)
-Hold everything in place to prevent sound from being heard by reducing vibration.
Negative Middle Ear Pressure Cause
Eustachian tube dysfunction
Negative Middle Ear Pressure Audiometric findings
-Type C tymp due to the eardrum being retracted into the middle ear space, creating less available space in the middle ear.
-Slight conductive hearing loss
Otitis Media
Infection of the mucous membrane lining in the middle ear.
Audiometric Findings of Otitis Media
-Flat bilateral conductive hearing loss
-Type B Tymp (flat)
-reduced static compliance
-absent acoustic reflexes
Cholesteatoma
-Occurs when skin is introduced into the middle ear cavity via a severely retracted TM
-May start as a middle ear infection
Facial Palsy
-Causes paralysis to the face
-May occur after chronic otitis media which can erode the fallopian canal leaving the facial nerve exposed to disease.
Patulous Eustachian Tube
-Tube is chronically open
-due to hormonal changes
-more common in women
-sound of breathing/chewing can travel up the tube
