anatomy of ear Flashcards
what is the medical term for outer ear
pinna / auricle
what is the external acoustic meatus
ear canal
what are the 2 structures that make up the outer ear
pinna
external acoustic meatus
where does the outer ear end
ear drum
where is the middle ear found
in the tympanic cavity
what 3 auditory ossicles/bones are found in the middle ear/ tympanic cavity
- malleus
- incus
- staples
what is the purpose of the malleus, incus and staples
transmit sound vibrations through the middle ear.
what is the middle ear usually filled with
air
what is the purpose of the middle ear/ what happens in the middle ear
- compression waves (sound waves) in the air cause tympanic membrane (ear drum) to vibrate
- movement is amplified and transmitted by the ossicles to the oval window where these vibrations are converted again into waves in the perilymph fluid of the inner ear
reflex contraction of the muscles in the middle ear can do what 2 things
- uncouple ossicles
- dampen sound sounds
what is the amplification factor of effective pressure in the middle ear and why is it this value
- x17
- the area of the oval window is about 17 times smaller than the tympanic membrane, with further amplification cause by lever action of malleus and incus
what muscle found in the middle ear is connected to the malleus
tensor tympani
how does the tensor tympani work to cause a dampening movement in response to loud noise
tensory tympani pulls the manubrium of the malleus medially, tensing the tympanic membrane (ear drum) and dampening movement in response to loud noise
(tympanic reflex)
where is the tensor tympani found
a muscle within the middle ear, located in the bony canal above the bony part of the auditory tube,
what is the stapedius muscle and its role
- connects to the staples
- dampness movement of stapes at the oval window
- a small muscle located inside the middle ear. It helps stabilize the stapes bone and is involved in regulating sound and protecting your inner ear from damage due to loud sounds
paralysis of the stapedius muscle with bell palsy (partial paralysis of facial muscles) can cause what pathology
hyperacusis
(reduced tolerance to sound)
what innervates the tensor tympani
mandibular division of trigeminal nerve
what innervates the stapedius
branch of facial nerve
both tensor tympani and stapedius are activated immediately prior to speaking and dampen snout to cochlea from the larynx
what is the smaller skeletal muscle in the body
- stapedius
what is the 2 functions of the chorda tympani nerve
- special sensory fibres for sweet and sodium chloride sensation from anterior 2/3 of tongue via linguinal nerve
- presynaptic parasympathetic fibres to submandibular ganglion innervating salivary glands
what is the pharyngotympanic / eustachian tube
a canal that connects the tympanic cavity (of the middle ear) to the nasopharynx
what type of cells line the pharyngotympanic tube
- ciliated columnar epithelium
what is otitis media
infection of the middle ear
can be severe or acute
why are children more prone to otitis media
the structure of the pharyngotympanic tube in kids is more horizontal so the pressure equilibration is less easy to achieve
find image of ear and label all the internal structures
find image and label all the structures of the temporal bone
The petrous part is a wedge shaped mass of bone located between the sphenoid and occipital bones within the cranial cavity.
what is mastoiditis
infraction affecting mastoid air cells
how does mastoiditis and otitis media related
mastoiditis is secondary to otitis media having spread from the middle ear to the mastoid air cells
how can you recognise mastoiditis from a ct scan
the side with mastoiditis no longer contains air and will appear grey instead of black as it is now filled with substance
if mastoiditis is left untreated, how could it further progress
may lead to osteomyelitis
- infection that spreads to bone
what are the 3 parts/ bony labyrinths of the inner ear
- semicircular canals
- cochlea
- vestibule
what are the functions of the inner ear
Making it possible for you to hear and helping you keep your balance.
semicircle canal and vestibule (help understand rotation/direction, acceleration/velocity)
cochlea (hearing)
what are the membranous labyrinth structures in the inner ear (4)
- article and saccule inside vestibbule
- cochlear duct
- membranous semicircular duct
what is endolymph
clear fluid filling the membranous labyrinth
what is perilymph
similar to CSF, surrounds the membranous labyrinth, filling the space between membranous tunnel and its contents and bony walls surrounding
The inner ear is the innermost part of the ear, and houses the vestibulocochlear organs. It has two main functions:
To convert mechanical signals from the middle ear into electrical signals, which can transfer information to the auditory pathway in the brain.
To maintain balance by detecting position and motion.
what fluid is found within the membrane labyrinth of the inner ear
endolymph
what are the 3 parts of the semicircular canal and how are they positioned
- anterior
- horizontal
- posterior canal
- they all sit perpendicular to each other
what is the purpose of the semicircular canal and how does it do this
balance and orientation
- When your head moves around, the liquid inside the semicircular canals sloshes around and moves the tiny hairs that line each canal. These hairs translate the movement of the liquid into nerve messages that are sent to your brain. Your brain then tells your body how to stay balanced.
what do you call the swelling in structure at the end of each semicircular canal
ampulla
what is the role of the utricle and saccule
sense linear head acceleration and head tilt, with the utricle detecting horizontal movements and the saccule sensing vertical motion.
They use small stones and a viscous fluid to stimulate hair cells to detect motion and orientation.
what is the name of the hair cells that detect movement
stereo cilia
note the oval window sits in the wall of the cochlea
how does the cochlea process noise
- oval window gets depressed by ossicles creating waves that travel through fluid of cochlea
- these waves cause the basilar membrane to move as well
- different sections of the basilar membrane respond to different frequencies of sound
- as waves travel down the membrane, they reach their peak at at the part of the membrane that responds to the freq of the sound wave made by original stimulus
- when the basilar membrane vibrates, the organ of cortical which sits on top of the basilar membrane has hair cells containing stereocillia
- movement of stereocillia opens ion channels and causes the release of neurotransmitters to propagate auditory signal to vestibulocochlea nerve that’ll carry auditory stimulus to the Brian to be perceived
what part of the cochlea translates the movement of the basilar membrane
organ of cortic (receptor of ear)
- sits onto of basilar membrane and has hair cells
- stereocillia is found collected at the top of the hair cell structure
