Structures and functions of the ear Flashcards
3 divisions of the ear
External Ear
Middle ear
internal ear
Which parts of the ear are responsible for hearing only, and which is responsible for hearing and balance?
External & middle ear - hearing only
Internal ear - hearing, and balance
What is the Auricle and what is its function?
The fleshy part of the external ear on the outside of your head.
Its shape collects sounds waves and directs them to the external auditory canal
Cerminious glands
The external ear is lined with these glands that produce cerumen, or ear wax
What is the purpose of cerumen?
It prevents foreign objects from entering the ear
What is the Tympanic Membrane and what is its function?
It separates the external ear from the middle ear and vibrates when sound waves reach it
It can be ruptured with an airplane change in altitude or when diving and can result in hearing impairment
Where are mastoid air cells located
The middle ear, part of the one passage from the middle ear
What is the auditory tube and what is its function
The other passage is from the middle ear. It equalizes air pressure between the middle and external ear cavity
3 auditory ossicles of the inner ear and their function
Malleus
Incus
Stapes
They form a physical bridge to transmit vibrations from the tympanic membrane to the oval window
What are the two muscles in the middle ear and what do they do?
The stapedius adn tensor tympani; they act as a reflex and dampen sounds that are too loud.
Oval window
A hole in the bony membrane that receives sound waves from the three auditory ossicles
The bony labyrinth
part of the inner ear with tunnels and channels inside the temporal bone
membranous labyrinth
a smaller set of tunnels inside the bony labyrinth
What are the 2 fluids in the inner ear, and what do they fill?
Endolymph - fills the membrainous labyrinth
Perilymph - fill sthe space between the membranous labrynth and bony labyringth
What are the three regions of the bony labyrinth, and which are responsible for balance v hearing?
Vestibule > balance
Semicircular canal > balance
Cochlea > Hearing
What are the three regions of the cochlea, and what fluid is each filled with?
Scala tympani > filled with perilymph
Scala vestibuli > filled with perilymph
Cochlear duct > filled with endolymph and contains the spiral organ
Spiral organ
Is made of inner and outer hair cells (sensory cells of hearing) that attach to tectorial membrane.
Cochlear ganglion
Groups of cell bodies that join to form the cochlear nerve, which then forms the vestibulocochlear nerve VIII
Can sound pass through a vacuum?
No, sound must pass through matter
Volume
Loudness - a function of amplitude
Pitch
Sound wave frequency
Timbre
resonance quality of a sound (why different instruments have different sounds)
How does sound work?
1) External air collects sound waves >
2) sends them to the tympanic membrane >
3) tympanic membrane cuasees 3 auditory ossicle (malleus, incus, stapes) to vibrate >
4) cause the perilumph and endolymph to vibrate >
5) causes a distortion of basilar membrane
6) Basilar membrane causes bending of stereocilia in inner hair cells in the spiral organ
What is the purpose of the round window
Protects the inner ear from pressure build up & dissipates sound waves
What is the chemical reaction of hearing?
1) The inner hair cells pull on tip links, openin gup k+ channels
2) Then calcium ions enter and further depolarize the ion
3) depolarization releases glutamate, stimulating action potentials in the vestibulocochlear nerve
Endocochlear potential
The K+ charge difference between the endolymph and perilymph
What is the neuronal path of hearing?
Vesibulocochlear nerve > Medulla oblongata > Inferior colliculi > Thalamus > Auditory cortex
Presbyacusis
Decrease in hair cells in cochlea causing age-related hearing loss
Conductive hearing loss
Problem with the transmission of sound waves from the external ear to the spiral organ.
Can remove the blockage or use hearing aids.
Sensorineural hearing loss
Spiral organ or neuronal pathways are damaged. Can use hearing aids
2 parts of the balance organ and their functions
static labyrinth > evaluated position relative to gravity
dynamic labyrinth > evaluates the movement of the heads
2 parts of the static labyrinth
Utricle
Succule
what are the names of the specialized epithelium in the utricle and succule
utricular macula
saccular macula
They resemble spiral organ
Otolith membranes
Respond to gravity by bending
What is the position of the 3 semicircular canals of the dynamic labyrinth
X Y Z axis
Ampilla
The base of semicircular canals
Crista ampularis
The specialized epithelium that lines the ampilla
Cupola
A gelatinous mass with hair cells embedded - a “float” -associated the ridge of the crista amuplaris that is displaced by movements
Neuronal pathway of balance
1) Neurons on macuale and crista >
2) converge to vestibular ganglion >
3) Join vestibulcochlear nerve >
4) Medulla oblongata >
5) CNS, Spinal cord
