The Ear Flashcards
Which bone houses the vestibule-cochlear apparatus
The petrosal temporal bone
Which two cranial nerves pass the internal aucostic meatus
The vestibulocochlaer and facial nerve
What is the ear the organ of
Hearing and equilibrium
What membrane separates the middle ear from the external ear
The tympanic membrane
Which structure joins the nasopharynx to the middle ear
The auditory tube
How does the external ear deal with the hearing process
The auricle and external aucostic meatus capture sound waves and direct them to the tympanic membrane
How does the internal ear process hearing
The semi-circular canals and the cochlea convert mechanical signals to electric signals which are transmitted to the brain via the vestbulocochlear nerve
What is the main sensory innervation of the external ear
Largely by the greater auricular and auriculotemporal nerves
What is the function of the external ear
Supportive function
- catches and funnels the sound into the external aucoustic meatus and then to the tympanic membrane and inner ear
What kind of epithelium is the external aucousti meatus lined with
Stratified squamous epithelium
What are cermunious glands
The modified sweat glands that secrete ear wax
What is the function of the ear wax and the hairs in the external aucostic meatus
To keep forgein bodes away from the tympanic membrane
How is the tympanic membrane held in the temporal bone
By a fibrocatilganeous ring
When looking in an otoscope of the tympanic membrane what is a key feature of a heathy ear and why is this?
A cone of light ( caused from light from the otoscope) this is health as it means there is no fluid accumulation or pathology
Which are the two small muslces oresent in the tympanic cavity ( middle ear)
The stapedius and the tensor tympani
What are the three ossicles of the ear
Malleus, incus and stapes
What is the function of he tensor tympani and the stapedius
They resit the movement of the ossicles protecting hte ear if there are loud sounds
What is the innervation to the stapedius
Nerve to stapedius - brach of the facial nerve
What is the nerve supply of the tensor tympani
Mandibular divsion of the trigeminal nerve
What does the end of the cartilagenouss tube of the auditory tube form
The torus tabuarius - in the wal of the nasopharynx
What is the function of the auditory tube
To connect the middle ear with the nasopharynx and to facialte pressure equalisation
Why can respiratory tract infections sometimes cause middle ear infections as well?
Due to the connection of the middle ear and the nasopharynx from the auditory tube which can often facialte infection spread
Patient has a Schwannoma( begnign tumour affecting CN8) requiring surgery at the internal aucostic meatus - which nerve is potentially at risk
The facial nerve
The facial nerve through its course gives off the greater petrosal nerve and chorda tympani - what are the functions of these nerves
Greater petrosal nerve sends parasympathetic fibres to the ptergopaltine ganglion
Chorda tympani - carrying parasympathetic fibres to submandibular ganglion and running with the lingual nerve. Taste to anterior 2/3 of the tongue
The facial nerve also sends off a small branch called the nerve to stapedius what does this do
This nerve functions to innervate the stapedius muscle which dampens the movement of Stapes which is an ossicle
Why is there a risk of infection between the middle ear and middle cranial fossa?
This is because the here is a thin roof of bone between these two areas, if the infection is very severe it can erode the bone and affect the vascular structures
Which ossicle does the tensor tympani attach to
Malleus
How re the mastoid air cells connected to the middle ear
Through mastoid antrum
Infections in the middle ear are common and what re they most often caused by
Obstruction in the auditory tube
Chronic ear infections may lead to the mastoid air cells causing a conditin called mastoiditis - why may surgeons be war of operating
Due to the close proximity of the facial nerve
What is the medical name for chronic ear infections
Otitis media
What does conductive hearing loss mean
When the issue is which transmission of sound mechanically via the ossicles rather than with the vestibulocochlear nerve
What is glue ear
Otitis media with effusion - tends to affect children more and it is a build up of fluid in the ear behind the tympanic membrane - affecting hearing
What organ does the inner ear contain
The vestubulocochealr organ which is concerned with reception of sound and maintenance of balance
What kind of fluid does the only labyrinth in the inner ear contain
Perilypmh
CN8 leaves the crnial fossae via the interal acoustic meatus and divides into two parts , what are these towparts and what are they responsible for
A cochlear nerve and a vestibular nerve
Vestibular nerve = equilibrium and balance
Cochlear =hearing
What is neural hearing loss
This is when the problem is with the nerve or a problem with the cochlea
Rather than the mechanical transmission of sound
Where does the information the vestibular nerve carries come from
The semicircular canals
Wha are some symptoms of damage to this nerve
Ataxia (clumsy voluntary movements)
Vertigo ( feels like everything is spinning enough to affect balance )
Nausea
This is because this nerve is responsible for balance o
