Middle Ear Flashcards
what CN is for hearing and balance
vestibulocochlear nerve (8)
what 4 structures make up the external ear
auricle, external auditory meatus, auditory canal and tympanic membrane
what is inside the middle ear
the 3 ossicles, air, and is lined with mucosa
where is the middle ear located
within the petrous part of temporal bone
where is the internal ear located
small cavities within petrous part of temporal bone
what is contained in the internal ear
sensors of motion and balance
what is the function of the middle ear
mechanical conduction of sound to fluid-filled internal ear
what is located inside the mastoid part of the temporal bone
air cells
what is the region called deep to the tegman tympani
epitympanic recess
what is the region called that is deep to the epitympanic recess
tympanic cavity
what feature in the middle ear does the tympanic plexus rest on and mark the position of the cochlea
the promontory
what are the 3 bones in the osseus chain
malleus, incus, and stapes
what ossicle sits in the oval window
the stapes
which ossicle is joined to the tympanic membrane
malleus
how many synovial joints are between the ossicles
2
what is the joint called between the stapes and the incus
incudostapedial joint
what is the joint called between the incus and malleus
incudomalleolar joint
what are the 3 external facial muscles associated with the auricle
superior, anterior, and posterior auricular muscles
what is the pinna or auricle
the visible part of the external ear
what is the helix
the folded over outside edge of the ear
what is the antihelix
forms a “y” shape where the upper parts of the ear are (medial from the helix)
what is the tragus
small prominence, in front of the concha and projects backward over the EAM
what is the concha
the hollow next to the external auditory meatus
where is the antitragus
below the tragus
what glands are for ear wax and where are they located
cerumen glands - around the EAM
what types of tissue make up the EAM
half bone and half cartilage and skin
what is the umbo
the most depressed part of the tympanic membrane
what is the tympanic membrane
“eardrum” a thin cone-shaped membrane that separates the external and middle ear
what is the function of the tympanic membrane
to transmit sound from the air to the ossicles
what covers the tympanic membrane laterally and medially
laterally- connective tissue/skin of auditory canal and medially- mucosa of middle ear
what does a normal tympanic membrane look like
gray, translucent, may have vascular streaks
how can an otoscope look inside the canal that is curved
you pull the auricle superiorly, posteriorly and slightly lateral to straighten out
what is microtia
congenital absence or deformity of auricle, absence of auditory canal and fusion of the ossicles
who usually gets microtia
females, unilateral
what is the cause of microtia
in utero ischemia of area of development, chromosomal aberrations, Treacher-Collins or Goldenhar syndromes, thalidomide, Accutane
what are the symptoms of microtia
small, malformed or absent ear, conductive hearing loss on affected side by 40-60%
what are the treatments for microtia
reconstruction (begin in summer before 1st grade) using rib cartilage for auricle
what is a complication of microtia
unpleasant cosmetic result
what is exostosis
benign bony growths of auditory canal related to cold water exposure
what is a symptom of exostosis
conductive hearing loss
what are treatments for exostosis
exostectomy (canalplasty) - postauricular approach allows complete removal of exostoses and has less risk to CN 7, the TMJ or tympanic membrane
what are complications of exostosis
water may become trapped between bony growths and tympanic membrane, causes ear infections
what 4 sensory nerves innervate the external ear
lesser occipital nerve (C2), great auricular nerve (C2, C3), auriculotemporal V3, auricular branch of CN 10
what nerve is the bulk of sensation for the auditory canal
auriculotemporal nerve of V3
what is the vasculature to the external ear
posterior auricular from ECA, anterior auricular branches from superficial temporal artery and a branch from the occipital artery
what is the blood supply to the auditory canal and lateral surface of the tympanic membrane
the deep auricular artery- branch from the maxillary artery
what are the paths for drainage for the external ear
posterior auricular vein + posterior division of retromandibular vein –> to the external jugular fain
Or the anterior auricular veins to the superior temporal veins
what is the drainage path for the auditory canal
deep auricular vein to the pterygoid venous plexus
what causes auricular hematoma
trauma to pinna (wrestling injury most common)- perichondrial vessels bleed and pool between perichondrium and cartilages
what are 2 symptoms of auricular hematomas
fluctuant swelling and pain
what is the treatment for an auricular hematoma
drainage
what is a complication of auricular hematomas
severe fibrous reaction will occur if blood supply to cartilages of auricle is not reestablished- resulting in “cauliflower ear”
what muscle is in the middle ear
tensor tympani
what is the superior wall of the middle ear called and what structure is near there
tegman tympani- middle cranial fossa
what is the lateral wall of the middle ear called and what structure is near there
membranous wall- auditory canal
what is the inferior wall of the middle ear called and what structure is near there
jugular wall- internal jugular vein
what is the medial wall of the middle ear called and what structure is near there
labyrinthine wall - internal auditory meatus
what is the posterior wall of the middle ear called and what structure is near there
mastoid wall- mastoid air cells
what is near the anterior wall of the middle ear
internal carotid artery, nasopharynx via pharyngotympanic tube
which 2 walls of the middle ear are thin
superior and inferior
what is the purpose of the mastoid air cells
reserve air supply or to lighten the mastoid
what is the tube that connects the middle ear to the nasopharynx
pharyngotympanic tube
what are 2 functions of the pharyngotympanic tube
equilibrate pressure in middle ear and to drain mucus from middle ear and mastoid cells
what 3 structures are continuous that allow for mucus drainage
middle ear, pharyngotympanic tube and mastoid air cells
what is acute otitis media
infection with inflammation and effusion- fluid builds up in middle ear and puts pressure on tympanic membrane
who is most likely to get an acute otitis medai
children by age 3 and people with a PT tube that is narrower, shorter, and immune systems that are underdeveloped
what causes an acute otitis media
viral infection, adenoids, PT tube dysfunction
what are symptoms of an acute otitis media
pain, fever, headache, clear fluid drainage, dizziness, and temporary hearing loss
what is the treatment for otitis media
most will clear up on own, antibiotics, and myringotomy tubes for recurrent infections
what are complications of an acute otitis media
ear drum rupture, mastoiditis, permanent damage of tympanic membrane and hearing loss
what is coalescent mastoiditis
acute, usually associated with acute otitis media, inflammation of mastoid air cells - infection that spreads beyond the mucus of middle ear
what is the cause of coalescent mastoiditis
usually incomplete antibiotic treatment for acute otitis media
what are 3 symptoms of coalescent mastoiditis
pain behind ear, protrusion of ear and fever
what is the treatment for coalescent mastoiditis
mastoidectomy (surgical drainage)
what are complications for coalescent mastoiditis
sigmoid sinus thrombosis, meningitis, abscesses, intratemporal involvement of CN 7 and/or labyrinth (causing sensineuronal hearing loss)
what is the purpose of the tensor tympani and tendon of stapedius muscle
to keep ossicles from vibrating too violently
which muscle dampens the vibrations of the tympanic membrane
tensor tympani muscle
which muscle dampens ossciallations of stapes
stapedius muscle
what innervates the tensor tympani
nerve to medial pterygoid from V3
what innervates the stapedius muscle
nerve to stapedius from CN 7, branch in facial canal
what are the 2 middle ear general efferents
nerve to stapedius (CN7) and nerve to medial pterygoid (V3)
what are the general afferents and visceral efferents of the middle ear
tympanic plexus: tympanic nerve (CN 9 in jugular foramen) and caroticotympanic nerves (from sympathetic ICA plexus)
what 2 nerves pass through the middle ear but do not innervate structures
lesser petrosal nerve (branches off tympanic plexus) and chorda tympani nerve (branch of CN7)
what 2 structures does the facial canal run between
cochlea and semicicular canals of internal ear
how many branches of CN7 that are given off in the facial canal are related to the ear
3 out of 4
what is the venous drainage for the middle ear
pterygoid venous plexus
what 3 structures are for balance
utricle, saccule, and semilunar circles
what structure is for hearing
cochlear duct
what 2 types of fluid are in the cochlear
perilymph and endolymph
what is the blood supply to the internal ear
labyrinthine artery from anterior inferior cerebellar artery or basilar artery
what is the venous drainage for the internal ear
labyrinthine veins to interior petrosal sinus or sigmoid sinus
what happens to the sound waves after they go through the external ear and auditory canal
they vibrate the tympanic membrane- moves handle of malleus- moves head of malleus- moves incus- and pushes stapes into oval window
what happens to the sound waves after they push the stapes into the oval window
cause waves in perilymph causing the round window to bulge laterally and trigger the cochlear receptors - CN 8 - brain
what are the 2 components of mechanical conduction
air or bone conduction
what are the steps for conduction
sound waves - external ear - ossicular chain - perilymph and cochlear duct
what is the path for sensorineural
vibration of cochlear duct receptors - cochlear component of CN 8 - brain
what happens if there is a deficit in air conduction
you will still have bone conduction and be able to hear some sound
what is the weber’s test
to test for unilateral conductive or sensorineural hearing loss
what is a normal result in a weber’s test
sound is heard loudest in center and equally in both ears, this can mean equal hearing loss on both sides
what is an abnormal Weber’s test
sound is louder on one side
what test is after the Weber’s test if there is an abnormal result
Rinne test- unilateral conductive hearing loss
what is a normal result for a rinne test
sound is loudest when tuning fork is next to ear and is quieter when tuning fork is placed on mastoid process
what is an abnormal result for a rinne test
sound is loudest when tuning fork is placed on mastoid process
