Sievert-Ear and Audition Flashcards
What makes up the external ear?
auricle and external auditory meatus
What does the external ear do?
Captures and funnels sound
What is the middle ear?
air-filled cavity behind the ear drum.
What is found in the middle ear and what do they do?
3 ossicles (malleus,incus and stapes), transfer ear drum vibration to oval window and fluid behind oval window
What is the inner ear?
fluid filed cochlea and vestibular apparatus
What is the function of the inner ear?
holds sensory hair cells for hearing and balance
Where do you find the semicircular canal?
inner ear
What many ducts make up the cochlea?
3 different ducts
Lots of functions of the inner ear also carry over to the (blank) system
vestibular
Where does the external auditory meatus come from?
the 1st brachial cleft
Where does the middle ear, auditory tube come from?
the 1st branchial pouch
Where does the malleus and incus come from?
the cartilage from the first branchial arch
Wher does the stapes come from?
the cartilage from the second branchial arch
What CN is associated with the malleus and incus? why?
CN 5
because Arch 1 is innervated by CN 5 and that is where the malleus and incus come from
What CN is associated with the stapes (means stirrup in latin colt in case you were wondering) and why?
CN 7 because arch 2 is innervated by CN 7 and this is where the stapes originates from
The bones of the ear develop via what process?
endochondrial ossification (cartilagenous model)
So the middle ear has the three ossicles which are the malleus, incus and stapes. What do these small bones do?
They transmit sounds from the air to the fluid filled labyrinth (cochlea)
What 2 small skeletal muscles alter movements of the ossicles?
tensor tympani and stapedius
How is the membranous labyrinth, hair cells and ganglion cells made and what are all of these a part of?
These are all part of the inner ear.
Made by the otic placode which will invaginate to form the otic pit/vesicle and statoacoustic ganglion
How do we get the surface ectoderm of the otic placode to make the inner ear?
it gets induced by neuroectoderm
How does the external ear keep bugs and bacteria out?
contain ceruminous glands that produce wax which is antibacterial
What are the lateral walls of the external ear made out of?
cartilagineous
What are the medial walls of the external ear made out of?
bone
Which part of the auditory canal is longer, the inferior or superior portion?
the inferior canal
Why is the external ear awesome at collecting sound?
How?
because it amplifies speech as well as collects it (1-3 khz X up to 100 fold)
via passive resonant properties
What part of your ear helps localize sound in the vertical axis?
the external ear
Explain how sound flows from outside the ear to the ovale window
the tympanic membrane will vibrate which is connected to the malleus. The malleus will transmit this vibration to the incus which will send it to the stapes which is attached to the ovale window.
Where is the vestibular nerve?
superior to the cochlea
Where does the external ear get sensory innervation?
from CN 5 (auriculotemporal) the cervical plexus (ventral rami spinal nerves i.e. lesser occipital and greater auricular) and small auricular branch of vagus to external tympanic membrane AND a small branch from CN 7
Where does the small auricular branch from the vagus go?
to the tympanic membrane
Where does the lesser occipital nerve and great auricular nerve come from? And what do they do?
the cervical plexus
they give cutaneous innervation to the external ear
What comes off of the vagus to give innervation to the external tympanic membrane?
the small auricular branch
How does the middle air maintain air in this cavity?
it has a connection to the outside world called the auditory tube.
What happens if you close the auditory tube?
your tympanic membrane will get sucked in and the middle ear will fill with fluid.
What is the point of the ossicles?
to create a mechanical advantage to allow for a slight movement of the malleus to cause a greater diversion of the stapes.
What is a second mechanical advantage that the ear has to transmit signals from the external ear into the inner ear?
The tympanic membrane is larger than the oval window
The oval window houses what kind of interface? So why is this significant?
a liquid interface
This is why we have mechanical advantages in the ear because we need to compensate for the loss of sound crossing the air/liquid interface
What is between each ossicle?
mini cartilaginous joints
What is the purpose of the middle ear?
amplifies sound signals, makes up for energy that is lost as sound moves from air into a liquid medium
What are the important amplification features of the middle ear?
size difference b/w tympanic membrane and oval window
mechanical advantage of bony lever system
Where the entrance to the mastoid antrum?
superior to the ossicles in the middle ear
Where is the round window?
inferior to the ossicles in the middle ear
What are the 2 muscles that help to reduce sound intensities by increase the stiffness of the apparatus?
stapedius muscle
tensor tympani
What does the tendon of the tenor tympani muscle connect to?
the malleus
where does the tensor tympani arise from?
the lateral membranous wall of the auditory tube.
How does the stapedius and tensor tympani reduce sound intensity?
they increase the tension on the tympanic membrane which limits the reflection and reduces the amount of sound
What cranial nerve innervates the tensor tympani?
V3
Will damage to he 7th nerve cause with hearing?
Leads to loss of differentiation b/w background noise and focused noise
What is the middle ear cavity continuous with?
mastsoid air cells
nasopharynx via auditory tube
How does the chordi tympani pass through the ear?
in the middle ear it crosses superior to the tensort tympani and inferior the malleus and incus joint
How does the facial nerve pass through the middle ear?
Over the stapes and medial to the lesser petrosal nerve
Where do you find the tympanic plexus?
on the cochlear prominatory
Explain how the tympanic nerve (branch of CN 9) gets through the middle ear
it goes into middle ear and forms the tympanic plexus on the cochlear promanatory and then ascends to form the lesser petrosal nerve, which go into the skull and exit at the formane ovale
Explain the pathway of CN 7 through the middle ear
CN7 is surrrounded by bone and continues down into the stapes and then just prior to leaving the sytoloid mastoid foramen, gives of the chordi tympani and goes over the malleus and under the incus and leaves via the petrotympanic fissure.
How does cranial nerve 9 exit the skull
through the jugular foramen
What does CN 7 do in the ear?
contributes a small sensory branch to the middle ear
What does the greater petrosal nerve do?
give preganglionic parasympathetics to lacrimal gland
Most of CN 7 passes through the (blank) at the (blank) ganglion. Then it leaves through the (blank)
semicanal of the facial nerve
geniculate
styloid mastoid foramen
Where is the malleus attached to the tympanic membrane?
on the medial side
What will be tympani membrane be like if there is an infection in the middle ear?
vibration of membrane is reduced,it appears red and a fluid level may be visible
Is it common to get infections of the middle ear?
yes
How do microorganisms enter the middle ear?
via the auditory tube
What kind of people are most susceptible to otitis media (middle ear infection)?
children with auditory tubes that are angled slilghtly superiorly towards the nasal cavity
What does this describe:
middle ear fills with fluid and tympanic membrane gets red and inflammed
otitis media
When you have a lot of water in your middle ear cavity, what kind of frequencies are preferred?
low frequency
If you have increased stiffness of the tympanic membrane (bulging of tympanic membrane) they what kind of frequencies are favored?
high frequency
Movement of the (blank) against the oval window causes vibration of fluid in the inner ear.
stapes
When the stapes gives movement to the oval window, how does the movement get further transferred into the inner ear?
sensory cells in the cochlea responds providing us with hearing :)
How do we get sympathetics into the middle ear cavity?
via the carotid plexus
What allows us to respond to movements of the head and provide balance?
sensory cells in the vestibular apparatus (part of inner ear)
What 2 kinds of lymph are found in the inner ear and where do you find them?
endolymph (scala media) and perilymph (scala vestibule and scala tympani)
What ion is found in high concentrations in the endolymph? Where do you find endolymph?
potassium scala media (cochlear duct)
What ion is found in high concentration in the perilymph?
sodium (a lot like plasma)
What kind of relationship does the ovale and round window have? please explain
recipricol
When the stapes pushes on ovale window, the pressure inside causes the round window to bulge out
The scale of vestibule is associated with what window?
Ovale (rememner oVale Vestibule)
What window is the scale of tympani associated with?
the Round window :)
So the middle ear is (blank) filled while the inner ear is (blank) filled
air
fluid
What is the apparatus for hearing?
cochlea
What is the apparatus for balance?
semicircular canal, utricle and saccule