Ear Anatomy and Embryology Flashcards
auricle
pinna
-external ear
helix, tragus, antihelix
nerve to pinna
greater auricular C2,3
lesser occipital C2,3
auriculotemporal V3, facial, vagus
lymph to pinna
deep cervical lymph nodes
external acoustic meatus
stratified squamous epithelium
-numerous ceruminous glands
lateral 1/3 cartilage - short in kids
medial 2/3 bony
blood supply external ear
posterior auricular a and v
superficial temporal a and v
otitis externa
inflammation of external ear
tympanic membrane
exterior - epidermis
interior - mucus membrane
umbo
concavity tympanic membrane
-from malleus
pars flaccida
superior - thin walled tympanic membrane
pars tensa
inferior - thick walled tympanic membrane
blood supply tympanic membrane
external - deep auricular
internal - anterior tympanic
both from maxillary a
innervation tympanic membrane
internal - glossopharyngeal - GVA tympanic branch
external - auriculotemporal V3 GSA majority / vagus minority
auricle embryo
first and second arches
- 6 auricular hillocks (3 each) fuse
- defects common with chromosome syndromes**
external auditory meatus embryo
first cleft
-meatal plug forms - 7th month degenerates
persistance - deafness - can be surgically removed
tympanic membrane embryo
external - ectoderm of first cleft
middle CT - mesoderm of first arch
internal - endoderm of first pouch
middle ear
tympanic cavity - mucus lined
within petrous portion of temporal bone
also contains auditory ossicles
roof tympanic cavity
tegmen tympani
separates epitympanic recess from middle cranial fossa
floor tympanic cavity
segment of temporal bone
separate from internal jugular vein**
lateral wall tympanic cavity
tympanic membrane
medial wall tympanic cavity
bony wall separating middle from internal ear
promontory - cochlea
oval window - contact stapes - transmits motion
round window - opens to scala tympani - pressure release
round window
opens to scala tympani
oval window
contacts stapes
transmits motion to inner ear
posterior wall tympanic cavity
temporal bone
- aditus ad andrum
- facial canal
mastoiditis
middle ear infection - spread to mastoid air cells
via aditus ad antrum**
then spread to middle cranial fossa
anterior wall tympanic cavity
temporal bone
-separate middle ear from carotid canal
opening for pharyngotympanic tube and semicanal
semicanal
passage of tensor tympani
anterior wall tympanic cavity
pharyngotympanic tube
auditory tube
balances pressure on external and internal sides of tympanic membrane
posterolateral 1/3 bony
anteriomedial 2/3 cartilage
tensor veli palatini
opens the membranous tube (CN V3)
malleus
contacts tympanic membrane
-creates umbo
incus
body - malleus
long limb - stapes
stapes
contact oval window
stapedius
contract in response to loud noise**
posterior wall tympanic cavity to stapes
dampens movement of ossicles
nerve to stapedius
facial CN VII SVE
tensor tympani
contract when chewing or speaning
cartilage of auditory tube to malleus
dampen movement of ossicles
nerve to tensor tympani
trigeminal V3 SVE
paralysis of middle ear muscles
hyperacusis - excessive hearing acuteness
due to loss of dampening
blood supply to middle ear
inferior tympanic a - ascending pharyngeal
anterior tympanic a - maxillary
posterior tympanic a - stylomastoid
superior tympanic a - middle meningeal
venous drainage - pterygoid plexus
CN IX
glossopharyngeal nerve
GVA and GVE-P to middle ear and part of auditory tube
tympanic branch- enters via tympanic canaliculus
-forms tympanic plexus
lesser petrosal nerve reforms from plexus
-exits hiatus for lesser petrosal nerve GVE-P
PS to parotid
CN VII
SVE to stapedius
enters internal acoustic meatus
chorda tympani give off before CN VII exits stylomastoid
chorda tympani exits petrotympanic fissure
chorda tympani
SVA to anterior 2/3 tongue (taste)
GVE-P to SL/SM glands
otitis media
inflammation of middle ear
-due to spread of infection from pharynx via auditory tube
facial nerve branches
nerve to stapedius - SVE
greater petrosal nerve - GVE-P to PPG
chorda tympani - GVE-P, SVA - taste and PS
middle ear embryo - first pouch
tympanic cavity and auditory tube
middle ear embryo - first arch
malleus, incus, tensor tympani muscle
middle ear embryo - second arch
stapes, stapedius muscle
S RULE
Second arch
Stapes
Stapedius muscle
congenital fixation of stapes
deafness
inner ear
petrous portion of temporal bone
-vestibulocochlear organ
modiolus
bony core around which cochlea spirals
osseous spiral lamina
anchors cochlear duct to modiolus
vestibule
contains utricle and saccule
bony labyrinth
has perilymph
membranous labyrinth
has endolymph
all innervated by CN VIII
endolymphatic duct
maintains volume and composition of endolymphatic fluid
utricle
horizontal acceleration
saccule
vertical acceleration
cochlear duct
organ of hearing
- vestibular membrane - roof
- basilar membrane - floor
- organ of corti - hair cells plus tectorial membrane
CN VIII
vestibulocochlear
-passes through internal acoustic meatus to enter inner ear
vestibular portion - semicircular canals, utricle, saccule
-proprioception
cochlear portion - cochlear duct
-sound
inner ear embryo - membranous labyrinth
otic placode (ectoderm) - otic pit - otic vesicle
inner ear embryo - bony labyrinth
vestibule, semicircular canals, cochlea
-surrounding mesenchyme