Microanatomy of ear Flashcards
Where are hearing and balance receptors (same receptor type) located in the ear?
- petrous part of temporal bone
- balance more detected at vestibular apparatus
- hearing more at cochlea
What epithelium lines the external auditory canal
Stratified squamous which contain hair follicles and sebaceous glands
What glands secrete ear wax?
ceruminous glands
What is the function fo the pinna?
collects and amplifies sound
What is the function of the Eustachian tube?
equilibrates pressure on either side of the eardrum
What is the function of the auditory ossicle?
- transmits vibration from tympanic membrane to oval window
- convert sound waves to mechanical vibration in tissue
- amplify the vibrations
What are the three ossicles?
Malleus connects to incus which connects to stapes
What are the two muscles in the ear which protect from loud sounds?
stapedius and tensor tympani which dampen sound by
work to pull the tympanic membrane and stapes to stop them vibrating
What are the two labyrinths which make up the inner ear?
- Bony labyrinth
- Membranous labyrinth
What is the fluid that flows through the bony labyrinth called?
perilymph
What are the two sensory regions of the inner ear?
Vestibular apparatus (balance, posture & movement) Cochlea (hearing)
What fluid flows through membranous labyrinth
endolymph
What is the difference in the compositions of perilymph and endolymph?
Peri - high Na+ and low K+
Endo - low Na+ and high K+
What is the function of the different compositions in the two fluids
allows for proper conduction of current
What are the two parts of the vestibule?
Utricle
Saccule
What is the function of the vestibule?
Use ‘hair cells’ within the Macula (sensory) region of utricle and saccule to detect linear acceleration and perceive direction of gravity
Through what cranial nerve will the vestibules send information through?
vestibulocochlear (VIII)
What is the function of the semicircular canals?
detect rotational movement of head and body
What are the three chambers found in the cochlea and what fluid would you find in each?
Cochlear duct - endolymph
Scala tympani - perilymph
Scala vestibuli - perilymph
What structure does the vestibular nerve connect to within the cochlea?
Organ of corti
What two membranes separate the chambers in the cochlea?
vestibular (cochlear duct and scala vestibuli) basilar membrane (cochlear duct and scala tympani)
What is the function of organ of Corti?
converts sound vibrations to nerve impulses
Describe the structure of the organ of corti?
Made up of
1) tectorial membrane (lies over the top)
2) outer hair cells (connect to tectorial membrane via sterocilia)
3) inner hair cells (connect to tectorial membrane via sterocilia)
3) pharyngeal and pillar cells
What is the function of the outer hair cells?
contract when stimulated, pulls on tectorial membrane
What is the function of the inner hair cells?
Trigger hearing by cochlear nerve
How is a the vibration sent by the stapes transformed into a nerve impulse?
- Stapes acts as piston against the oval window
- creating a pressure wave which moves through the perilymph of scala vestibuli
- pressure wave can pass through the vestibular membrane into cochlear duct
- then through basilar membrane to perilymph of scala tympani
- movement within the endolymph results in displacement of the stereo cilia of the outer hair cells
- outer hair cells contract pulling the tectorial membrane
- tectorial membrane then shakes inner hair cells
- Neurotransmitters within inner hair cells stimulate cochlear nerve
Where in the cochlear and high and low frequencies detected?
high frequencies are detected in the apex (travel furthest down cochlea)
Low frequencies are detected at the base (Start of cochlea), narrower and stiffer here which is why responds best to low frequencies
Where in the brain do impulses from the cochlear nerve travel to?
auditory cortex
