Anatomy and histology of the ear Flashcards
in an otoscope view what does the sensory for the: Anterior portion
CN V3, Auriculotemporal Nerve
in an otoscope view what does the sensory for the: posterior portion
C3 Great auricular nerve
in an otoscope view what does the sensory for the: superior portion
CN VII
in an otoscope view what does the sensory for the: inferior portion
CN X Arnold nerve
can cause the arnold cough reflex by touching this
In the cough reflex what is the efferent nerve and what is the afferent nerve
efferent: Vagus and phrenic nerve
afferent: vagus Nerve
what produces wax in the external auditory ear canal (external acoustic meatus)
ceruminous glands
How is the External acoustic meatus broken down
outer 2/3 soft connective tissue and cartilage
inner 1/3 is skin on bone
only place in body where the skin and the periosteum and bone exist directly on top of each other
no connective tissue
therefore bleeds easily
what is the tympanic membrane made up
semitransparent membrane
outside layer lined with stratified squamous epithelium
inside layer lined with simple cuboidal epithelium
has concavity
moves with sound and transmits to ossicles
Parts of the tympanic membrane
Handle of malleus Umbo Pars flaccida anterior and posterior malleolar fold cone of light annulus Pars tensa
what quadrant is the cone of light found in
2nd quadrant where the innervation is done by Vagus Nerve
What are the walls of the tympanic cavity
roof (superior): Tegmental wall floor (inferior): jugular wall Laterally: membranous wall Medially: Labyrinthine wall Posteriorly: mastoid wall anterior: carotid wall
what are the two parts of the tympanic cavity
Tympanic cavity proper
Epitympanic recess
What are the three ossicles in the tympanic cavity and how are they attached
Malleus which is attached to the tympanic membrane
Incus in the middle
stapes that attaches to the oval window
What nerves travel through the tympanic cavity
Tympanic nerve (CN IX) Tympanic plexus Lesser petrosal nerve Facial nerve (runs next to in the labyrinthine wall) chorda tympani
what makes up the pharyngotympanic tube and what is its function
Connects the tympanic cavity (middle ear) with the nasopharynx
distal 2/3 boney
proximal 1/3 catilage
functions to equalize the pressures
-creates that ear popping sensation
What muscles expand the pharyngotympanic tube
Levator veli palatine: contracts longitudinally which pushes against one wall
TEnsor veli palatine: pulls on the other wall
how much does the ossicles amplify the force on the tympanic membrane
10x
Action and innervation of the tensor tympani muscle
Pulls on handle of the malleolus to tense membrane and reduce amplitude
inn: CN V
Action and innervation for the stapedius muscle
Pulls stapes posteriorly tightening annular ligament attaching it to the window
reduces oscillatory range and prevents excessive movement of stapes
inn: CN VII
What does it mean if the tympanic membrane is tight
Need more energy to make vibration (reduces amplitude)
What is the bony labyrinth
This is the cavity within the petrous region of the temporal bone
it is lined with endosteum and is seperated from the membranous labyrinth by perilymph
is considered the canals
what is the membranous labyrinth and its two functions
made of small sacs and tubes within bony labyrinth
forms a continuous space enclosed with epithelium
2 sections with two different jobs
- cochlear duct
- utricle, saccule, semicircular ducts
is considered the ducts
what are the three soft tissue canals that make up the cochlear duct
scala media : middle compartment that contains endolymph
-borders vestibular membrane, tectorial membrane, basilar membrane and the stria vascularis (makes endolymph)
Scala vestibuli: contains perilymph
moved by stapes at the oval window and is continuous with the scala tympani
scala tympani: connected to the round
full of perilymph
where is the organ of corti located
found on the floor of the scala media resting on the basilar membrane
WHat does the outer spiral lamina do
inner spiraling bony shelf that serves to support the tectorial membrane and the spiral ganglia
What is the organ of corti and how does it work
composed of haircells,
inner and outer phalangeal cells (support cessl)
and pillar cells (support cells)
one row of inner hair cells
3 rows of outer hair cells
when the basilar membrane vibrates with sound it causes the stereocila attached to the tectorial membrane to move opening or closing K+ channels
What is the function of the external ear
catches sound waves and directs them to the external auditory meatus and then to the tympanic membrane
can also check an individuals temperature here
What is the function of the middle ear
THe middle ear takes sound waves and turns it into physical movement
also is important in changing the volume of the ear by tensing or relaxing the tympanic membrane
also important in equalizing the pressure in the ear and nasal cavity
What is the inner ears function
The inner ear is responsible for balance
also is important for taking external sound waves and transforming them into usable information fro the brain
The path of the sound wave when it enters the cochlea
1) stapes moves the oval window causing fluid pressure wave formation in the perilymph of the scala vestibuli
2) wave distorts the vestibular membrane causing pressure wave within the endolymph of the scala media
3) this displaces the basilar membrane and distorts sterocila of hair cells
4) pressure in the perilymph is transfered to scala tympani and exits via the round window
How do the semicircular canals and ampulla work
there are three canals in three different axis
-Ant-sagital
-post- Coronal
transverse- horizontal
endolymph is filled and it is connected to the utricle
at the end of the canals they have aampulla which has a gelatinous like cap called a cupulla
there are innervated hair cells with sterocilla that are attached to the cupulla so that if the cupulla moves it moves the haircells
serve as sensors for rotational velocity
What is found in a utricle and a saccue
Vestibule contains a saccule and utricle
each contain a macula
-this is comprised of a cluster of hair cells with stereocilia with overlying gelatinous membrane called the otolithic membrane
the otolithic membrane is then covered with calcium carbonate/protein crystals called otoconia
What is the purpose of the utricle
linear acceleration and head tilts in horizontal plane
-U trip forward
What is the purpose of the saccule
Linear acceleration and the head tilts in vertical plane
suck up
what happens if the stereocilia move towards the kinocilium
there is a depolarization because of the opening of the K+ channels
What happens if the stereocilia move away from the kinocilium
there is hyperpolarization because of the closing of the K + channels
What drug causes ototoxicity to these hair cells
some types of antibiotics
Charachteristics of Perilymph
Composition similar to CSD, High in Na+ and low in K+ and protein
drains via the perilymphatic duct into the subarachnoid space
originates from periosteum
between Bony and membranous labytinths
Characteristics of endolymph
High in K+ and protein but low in Na+
originates from stria vascularis
Drains via endolymphatic duct into venous sinuses
found within membranous labyrinth
and in the corticolymphatic space
What happens if the perichondrium is sheared off the elastic cartilage in the external ear
get hematoma and necrotic cartilage
then you gen cartilage growth via chondrogenesis
presents as cauliflower ear
Damage to tympanic membrane
often due to:
medial ear pressure because of fluid or barotrauma
most heal but need follow up perhaps with antibiotics
Mastoiditis
Infection of mastoid cells
can spread into cranial fossa via petrosquamous cranial suture
treated with antibiotics
Otitis media
Ear infection
ear ache with possible fluid or pus in middle ear due to inflammation or infection
tympanic membrane appears red and bulged
fluid maybe visible through membrane
untreated can impair hearing and scarring of auditory ossicles
Menieres syndrome
experience dizziness, vertigo, high pitched rushing or roaring sound (tinnitus) and fluctuating hearing loss
associate with increase endolymph volume leading to abnormal signaling
treat with medication
or surgical ablation
similar symptoms to viral labyrinths but are resolved within a week
hearing loss
lots of causes
conductive hearing loss in outer or inner ear:
fluid build up, otits, excessive wax, otoscleosis
sensorineural hearing loss: reduction in sound level and/ or fidelity due to damage to inner ear or auditory nerve
affects hearing at different frequencies and intensities
-age related
-noise induced
Central hearing loss: problem in CNS
