Ear Flashcards
2 main functions of ear
equilibrium (balance) - vestibular system
hearing - cochlear system
external ear (pinna/auricle) structures
helix antihelix antitragus lobule (no cartilage) external acoustic meatus
external ear injury
Bleeding within the auricle resulting from trauma –> auricular hematoma
compromises blood supply to the cartilage. If untreated (by aspiration of blood) –> fibrosis –> deformed auricle (the cauliflower ear)
sensory innervation of external ear
auriculotemporal n. (V3): anterior helix, tragus
lesser occipital n. (C2)
greater auricular n. (C2, C3)
also CN VII and X (small contribution, overlap)
Arnold’s reflex
cough reflex initiated by stimulating CN X around external ear
auricular m.
superior auricular m.
anterior auricular m.
posterior auricular m.
supplied by motor br. CN VII (temporal br., posterior auricular br.)
blood supply to external ear
superficial temporal a.
posterior auricular a.
deep auricular a. –> pt of external acoustic meatus
venous drainage of external ear
superficial temporal v. –> __________
superficial temporal v. –> RETROMANDIBULAR V.
venous drainage of external ear
posterior auricular v. –> __________
posterior auricular v. –> EJV
lymphatic drainage of lateral top half of external ear
to superficial parotid nodes
lymphatic drainage of medial top half of external ear
to mastoid nodes
lymphatic drainage of bottom of external ear
to superficial cervical nodes
external acoustic meatus has both a _____ and _____ portion
lined with skin containing which types of glands?
external acoustic meatus has both a CARTILAGINOUS and BONY portion
lined with skin containing SUBACEOUS and CERUMINOUS glands
tympanic membrane
separates external and middle ear
set in sulcus of temporal bone
oriented laterally, anteriorly, and inferiorly
captures changes in air pressure (sound) and transfers to bones of middle ear
otoscopic examination
Pull helix posterosuperiorly to straighten external acoustic meatus to view …
- tympanic membrane
- lateral process of malleus
- umbo (handle/manubrium of the malleus poking into the pars tensa)
- pars flaccida
- light reflex triangle radiates anteroinferiorly.
sensory innervation to lateral (external) surface of tympanic membrane
CN V3, VII, X
sensory innervation to medial surface of tympanic membrane
CN IX
sensory fibers from CN IX get to inner surface of ear via the
tympanic n. of Jacobsen
tegmen tympani
roof over middle ear
separates cranial and tympanic cavities
arcuate eminence
elevated area on petrous portion of temporal bone
overlays semicircular canals
middle ear bones (ossicles)
malleus
incus
stapes
(all 3 function in conduction of sound thru middle ear)
posterior process on head of malleus articulates w/ body of ____
posterior process on head of malleus articulates w/ body of INCUS
(ice cream scoop + cone)
tensor tympani m.
innervation/origin/insertion
V3
tendon inserts onto handle of malleus
originates off cartilaginous portion of pharyngotympanic tube and part of the sphenoid GW
lenticular process of incus articulates w/ ____
lenticular process of incus articulates w/ STAPES M.
stapedius
innervation/origin/insertion
CN VII
tendon inserts onto neck of stapes
originates off walls of pyramidal eminence
paralysis of stapes
xs acuteness of hearing (hyperacusis)
poss due to CN VII lesion
middle ear blood supply
anterior tympanic a. (off 1st pt. maxillary a.)
middle ear lymphatic drainage
superior deep cervical nodes
middle ear innervation
CN IX (sensory to INNER surface tympanic membrane)
some CN V, IX, X (rest of middle ear)
parasympathetic (CN VII)
membranous wall of middle ear
lateral
- chorda tympani, passes over tensor tympani m.
segmental wall of middle ear
superior
- tegmen tympani
- epitympanic area
labyrinthine wall of middle ear
medial
- lateral semi-circular canal
- facial canal
- processus cochleariformis
- oval window (fenestra vestibuli)
- promontory
- round window (fenestra cochlea)
oval window
communication between middle and inner ear (into scala vestibuli of the cochlea)
base of stapes inserts onto here
on labyrinthine wall
promontory
right below oval window, on labyrinthine wall
1st basal turn of cochlea that bulges out into middle ear
has tympanic plexus (where tympanic n. of Jacobsen comes thru)
round window
secondary tympanic membrane, on labyrinthine wall
(blocked from scala tympani by a membrane)
alleviates pressure from oval window and stapes (oval membrane moves in –> round window moves out –> fluid moves into cochlea –> moves inner hair cells –> hearing)
jugular wall of middle ear
inferior
- jugular fossa (IJV runs past)
mastoid wall of middle ear
posterior
- facial n. runs thru
- aditus
- pyramidal eminence (encloses stapedius m.)
aditus
opening from middle ear to mastoid air cells
carotid wall of middle ear
anterior wall
- carotid canal (internal carotid a. travels right in front of this wall)
- opening of pharyngotympanic tube (Eustachian tube)
- semi-canal for tensor tympani
processus cochleariformis
tensor tympani m. makes a turn around this
contraction of which m. open the pharyngotympanic tube ate equalize pressure?
tensor and levator veli palatini
^also involved in draining middle ear
otitis media
- infection of middle ear
- bulging, red tympanic membrane and visible air-fluid meniscus behind it
- may block Eustachian tube due to mucosal inflammation
- untreated –> scars ossicles –> hearing loss
mastoiditis
infections travel thru aditus into mastoid air cells
- especially in children, otitis media spreads superiorly thru petrotympanic fissure causing osteomyelitis of tegmen tympani (roof of middle ear)
1st arch ear structures
malleus
incus
tensor tympani
2nd arch ear structures
stapes
stapedius
1st cleft ear structures
external acoustic meatus
1st pouch ear structures
pharyngotympanic tube
middle ear cavity
otic placode ear structures
membranous labyrinth in inner ear
tympanic membrane forms where during development?
at interface of 1st pouch and 1st cleft
cochlea contains which ganglion
spiral ganglion (DRG equivalent for CN VIII)
labyrinthine a.
- off the anterior inferior cerebellar a.
- travels thru internal acoustic meatus to supply INNER ear
canals within the inner ear form the _______ labyrinth
canals within the inner ear form the BONY labyrinth (fluid-filled, perilymph)
membranous labyrinth
membrane enclosed space within the bony labyrinth
suspended by delicate filaments
fluid-filled, endolymph
2 parts: vestibular labyrinth, and cochlear labyrinth
endolymphatic duct
from endolymphatic sac, fills up all parts of membranous labyrinth with endolymphatic fluid
perilymphatic space is connected to the _________ which is continuous w/ the subarachnoid space
perilymphatic space is connected to the COCHLEAR AQUEDUCT which is continuous w/ the subarachnoid space
(perilymph has similar consistency to CSF)
endolymph function is important for function of inner ear, how?
if pressure of endolymph too great, or if ionic concentration is off –> hair cells can’t move –> tinnitus, hearing loss, vertigo
Meniere’s syndrome
xs endolymph production or blockage of endolymphatic duct
–> recurrent tinnitus, hearing loss, vertigo
tiny hole just below internal acoustic meatus
for cochlear aqueduct
continuous w/ subarachnoid space
what is the sliver shape on ridge of bone, just above sigmoid sinus?
vestibular aqueduct
conveys endolymphatic duct (conveys endolymphatic fluid thru temporal bone)
there will be little pouch just underneath the dura for this
vestibular labyrinth
semicircular ducts
utricle
saccule
utricle and saccule
- contain hair cells sensitive to gravity and linear movement of head
- hair cells concentrated in areas called maculae
- hair cells embedded in jelly containing otoliths which pulls jelly in direction of gravity
- sensitive to movement in same plane as macula
utricle macula
horizontal plane
saccule macula
vertical plane
semicircular ducts
anterior, posterior, and lateral duct
sensitive to ROTATIONAL MOVEMENT of head
hair cells concentrated in ampullary crest within the ampulla
balance and positional awareness are integrations of which systems
vestibular and visual systems
anterior (superior) semicircular duct
responsive to nodding head yes
lateral (horizontal) semicircular duct
responsive to shaking head no
posterior semicircular duct
responsive to cartwheels, more angular rotation
motion sickness
- Maculae of membranous labyrinth are static organs, filled with otoliths which bend the hair cells to stimulate the vestibular nerve providing motion awareness.
- If the vestibular stimulation is disproportionate or there is discordance between visual input and vestibular input, motion sickness results.
(stopped turning, but have sensation of turning in opp direction as moving fluid directs hairs in opp direction)
modiolus
inner core of bone in cochlea which houses spiral ganglion
cochlear duct contains
endolymph
scala vestibuli and scala tympani contain ____ fluid
scala vestibuli and scala tympani contain PERILYMPH fluid
mechanical energy transmitted through the oval window causes vibrations within fluids of _________
mechanical energy transmitted through the oval window causes vibrations within fluids of COCHLEA
organ of corti
senses vibrations within fluids of the cochlea that were transmitted through the oval window
inner hair cells of cochlear system
- afferent innervation
- stereocilia in endolymph
outer hair cells of cochlear system
- afferent and efferent innervation
- stereocilia embedded in tectorial membrane
basilar membrane
resonant structure
dif parts of membrane have dif physical properties
regions of the basilar membrane vibrate in response to certain frequencies
movement of membrane bends sterocilia
sensorineural hearing loss
- defects or damage to cochlea or cochlear n.
presbycusis and high tone hearing loss
aging and persistent exposure to excessively loud sounds
inner hair cells at basal end= most susceptible to damage
difficulty hearing consonants (s, f, h, th, k, p), or in loud situations
consecutive hearing loss
loss of sound conduction from external or middle ear
impaired movement of oval or round window
cochlear implant
processus cochleariformis
bump where medial wall of middle ear joins w/ anterior wall, forms fulcrum for tensor tympani m. as it comes across middle ear
pyramidal eminence
small projection on mastoid wall of inner ear, immediately above oval window
encloses STAPEDIUS m.
the ___ bone transmits movement to the oval window
the STAPES bone transmits movement to the oval window
Locating bony opening of pharyngotympanic tube at base of skull
just posterior to foramen ovale and foramen spinosum, look for groove with a hole
pharyngotympanic tube is easily blocked by swelling of…
its mucosal membrane
each semicircular duct has an expanded part at the lateral end, called the ampulla, where it joins the _____
utricle
utriculosaccular duct
- part of the membranous labyrinth of the inner ear
- connects 2 parts of the vestibule, the utricle and the saccule
- continues to the endolymphatic duct and ends in the endolymphatic sac
ductus reuniens
connects the lower part of the saccule to the cochlear duct
tectorial membrane
gelatinous membrane, stereocilia embedded within
scala media
cochlear duct
____ hair cells act as cochlear acoustic amplifiers
OUTER hair cells act as cochlear acoustic amplifiers
describe the 2 ends of the basilar membrane
basal end (narrow, stiff, HIGH pitch sounds)
apical end (wide, floppy, responsive to LOW sounds)
