Hearing Flashcards
What are the two aspects of hearing?
Distinguishing between different sounds
Localisation (locating source)
Two aspects of language?
Production
Comprehension
Purpose of outer ear
- Detects air vibration
- Functions in protection, localisation and amplification
Middle ear functions
- Detects mechanical vibrations
- Functions in impedance matching
- Pressure equalisation
- Inner ear stimulation
What is impedance matching?
Matching the air vibration to the vibrations in the cochlear
How is pressure equalisation done?
Via Eustachian tube
How is inner ear stimulation done?
Via stapes
What are the functions of the inner ear?
- Detects mechanical, hydrodynamic and electrochemical signals
- Functions in sound filtering and signal transduction, converting the signal to send it to the brain
- Maintain balance by detecting position and motion
What is the anatomy of the outer ear?
(Structures between outer ear and the tympanic membrane)
- cartilages
- concha
- external acoustic meatus
What is the concha?
depression in middle that acts to direct sound into external acoustic meatus
What is the external acoustic meatus?
- a sigmoid shaped canal
- extends from concha to tympanic membrane
- supported by cartilage and temporal bone
What is the basic anatomy of the middle ear?
(Tympanic membrane to beginning of the cochlea)
- tympanic membrane
- umbo
- malleus (1/3 of the middle ear ossicles)
- incus (1/3 of the middle ear ossicles)
- stapes (1/3 of the middle ear ossicles)
- start of the eustachian tube
What is the tympanic membrane?
Sheet of thin, fibrous tissue that vibrates when it is hit with sound waves (i.e. ear drum)
What is the umbo?
A depression in the middle where the malleus attaches and extends upwards from.
Where does the malleus attach?
At the umbo on the TM and then on the incus
What 3 bones make up the middle ear ossicles?
Malleus
Incus
Stapes
What is the Eustachian tube?
- Cartilaginous and bony tube
- Drains into nasopharynx
- Functions to equalise pressure of the middle ear to match that of the external acoustic meatus
What is the basic anatomy of the inner ear?
(Beginning of cochlear to internal acoustic meatus)
- found within petrous part of temporal bone
- ‘bony labyrinth’ formed of:
- bony cavities
- vestibule
- cochlea
- semi-circular canals
- ‘membranous labyrinth’
Describe the bony cavities of the bony labyrinth of the inner ear
Series of bony cavities filled with periosteum and containing a fluid called perilymph
Describe the vestibule of the inner ear
- Central part
- Connected to both cochlea and semi-circular canals
- Contains the oval window where the middle ear connects to the inner ear via the stapes
Describe the cochlea of the inner ear
- Houses the cochlear duct
- Twists upon itself around a central portion of bone
- Produces a cone shape that points in the anteriolateral direction
- Contains 3 canals
- Contains the organ of Corti
What is the cochlear duct?
The auditory part of the ear
What are the 3 canals in the cochlea?
Cochlear duct (scala media)
Scala vestibuli
Scala tympani
What is the organ of Corti?
The receptor responsible for hearing
What are the semi-circular canals?
- anterior, lateral and posterior canals
- they contain the semi-circular ducts responsible for balance
What is responsible for balance?
Semi-circular ducts in the semi-circular canals of the inner ear
What is responsible for hearing?
The organs of Corti in the cochlea
What is the membranous labyrinth of the inner ear?
- lies within the bony labyrinth and filled with a fluid called endolymph
- made up of 3 cochlear canals
What are the 3 cochlear canals of the membranous labyrinth?
- saccule
- utricle
- semi-circular ducts
Where is the organ of Corti found?
Between the Scala tympani (canal of the cochlea) and the vestibule
What is the structure of the organ of Corti?
- Composed of mechano-senosry cells known as hair cells
- On basilar membrane, 3 rows of outer hair cells and 1 row of inner hair cells
What is the role of the inner hair cells in the organ of Corti?
Auditory discrimination
What are the cilia like in the inner hair cells of the organ of Corti?
They are not embedded in the tectorial membrane
What is the role of the outer hair cells in the organ of Corti?
Frequency tuning and amplification of sound signals
What are the cilia like in the outer hair cells?
They are embedded in the tectorial membrane.
How are the sound waves converted?
Vibration to electrical signals via electrical transduction