Auditory System 1: Structure & Function of the Middle & Inner Ear Flashcards
The auditory system is designed to transform _________ into ________ activity and ultimately to ______________ that are transmitted to the ______ to provide us with what we call hearing
- acoustic information
- mechanical
- electrochemical signals
- brain
The auditory system is divided into sections:
- outer ear
- middle ear
- inner ear
- auditory nerve
- central auditory pathways
Outer Ear Structures:
- pinna
- external auditory meatus (canal)
Middle Ear Structures:
- tympanic membrane
- tympanic cavity
- ossicular chain
- with all associated muscles, ligaments, and tendons
- Eustacian tube
Inner Ear Structures:
- oval window
- cochlea
- vestibular structures
Describe the Pinna:
- Skin-covered cartilaginous structure
- Channels sound waves into ear canal
- Pits, tags, or other malformations of the pinna indicate issues with ear development that may affect hearing
Describe the Ear Canal (External Auditory Meatus):
- From concha to eardrum
- Outer third is cartilaginous
- Inner two-thirds is bony
- The skin of the cartilaginous portion is thick and contains wax and oil glands:
- lubricate the canal
- protect the ear from foreign objects and debris
- Deep ear canal stimulation can cause referred sensation to vagus nerve making people cough
What function do the pinna and ear canal both share?
provide a boost in high frequency sound intensity
The handle of the malleus is directly attached to the _____________, which vibrates in response to ________________ funneled in by the external ear
- tympanic membrane
- sound pressure waves
- The malleus is attached to the ______, which is attached to the ______.
- The footplate of the stapes directly contacts the ________ on the inner ear.
- incus; stapes
- oval window
How do ossicles of the middle ear amplify sound vibration?
- lever mechanism
- area difference between the tympanic membrane & the footplate of the stapes
- This increases the force per unit area of the vibrations of the footplate of the stapes on the oval window of the inner ear
Describe the protective feedback mechanism for loud sounds:
- dampens the vibration of the ossicles
- activation of two muscles:
-
tensor tympani
- attached to the handle of the malleus
-
stapedius muscle
- attached to the neck of the stapes
-
tensor tympani
- When these muscles contract, vibration of these ossicles are reduced
- tensor typani = trigeminal nerve
- stapedius muscle = facial nerve
What are the functions of the inner ear?
- hearing
- balance
The inner ear is contained in the __________ of the temporal bone, and is encased in a bony structure called the ____________.
- petrous apex
- osseous or bony labyrinth
Labyrinth:
3 Sections
- vestibule
- cochlea
- semicircular canals