Ear anatomy and embryology Flashcards
What structures make up the external ear
auricle (pinna), external acoustic meatus and tympanic membrane
what is the structure of the auricle
cartilages (elastic)
depressions
lobule
what are the cartilages that make up the auricle
helix tragus and antihelix
what are the depressions that make up the auricle
concha, scaphoid fossa
what are the lobules made of in the auricle
fibroelastic tissue
what is the blood supply to the external ear
posterior auricular a and v
superficial temporal a and v
what inn the external ear
great auricular C23 and lesser occipital C23
auriculotemporal from V3 and VII and X
describe lymph drainage from auricle
mastoid, parotid lymph to deep cervical lymph
where does the external acoustic travel from and to
thru tympanic portion temporal bone to the tympanic membrane
what type of epithelium lines external auditory meatus
stratified squamous epi with numerous ceruminous glands
what part of the external acoustic meatus is cartilage? bone?
lateral 1/3 cartilage medial 2/3 bony
what is the blood supply of the external acoustic meatus
posterior auricular a and v
superficial temporal a and v
deep auricular a
what inn the external acoustic meatus
auriculotemporal n V3
vagus n
where does lymph from external acoustic meatus drain to
deep cervical lymph
what is otitis externa
inflammation of the external ear
what is the function of the TM
convert sound waves into vibrations of middle ear ossicles
what is the structure of the TM
semitransparent fibroelastic membrane
separates external and middle ear
covered by epidermis externally, mucus membrane internally
directed anteriorly and inferiorly
what is the central concavity called in the TM
umbo
what is the superior thin walled portion of TM called
pars flaccida
what is the infeiror thick walled part of TM called
pars tensa
describe blood supply to TM
external by deep auricular branch of maxillary
internal from atnerior tympanic branch of maxillary
what inn the TM
external- auriculotemporal n V3 and vagus
internal- IX
What is the aruicle derived from embryologically
mesencyme of 1st and 2nd pharyngeal arches
and 6 auricular hillocks that fuse
defects of the auricle are common with what type syndromes
chromosomal
what is the external auditory meatus derived from
1st pharyngeal cleft
meatal plug forms from proliferation of epithelial cells
when does the meatus plug of the external auditory meatus degenerate
7th month
What does persistence of the meatal plug cause
deafness
what is the TM derived from embryologically
external from 1st pharyngeal cleft
middle CT from mesoderm of 1st arch
internal from endoderm of 1st pouch
What is in the middle ear
tympanic cavity, mucous membrane lined space with petrous portion of temporal bone and auditory ossicles
what is the function of the middle ear
transfer sound from gas to liquid medium
amplify sound waves
protective against loud sounds
What is the roof of the tympanic cavity
tegmen tympani, separates epitympanic recess from middle cranial fossa
what makes up the floor of tympanic cavity
segment of temporal bone separating middle ear from internal jugular vein
what makes up the lateral wall of tympanic cavity
TM
What makes up the medial wall of tympanic cavity
bony wall separating middle form inner ear
What is the promontory of the medial wall of tympanic cavity
mound of bone created by cochlea
What is the oval window
opens to vestibule of inner ear
contacted by stapes that transmits motion
what is the round window and function
opens to scala tympani, covered with thin membrane
acts as pressure release valve for fluids of internal ear
what makes up the posterior wall of the tympanic cavity
temporal bone
what is the aditus ad antrum
entrance to mastoid antrum
what is the facial canal in the posterior wall of tympanic cavity
passage for facial n
what is mastoiditis
middle ear infection that can spread to mastoid air cells and then spread superiorly into middle cranial fossa
What makes the anterior wall of the tympanic cavity
segment of temporal bone separating middle ear from carotid canal
what openings are in the anterior wall of tympanic cavity
opening for pharyngotympanic tube and semi canal for tensor tympani
what is the pharyngotympanic tube
auditory tube (eustacian tube)
what is the function of the auditory tube
balance pressure on external and internal sides of TM
what parts of the auditory tube are cartilage or bone
posterolateral third is bony
anteromedial 2/3 cartilaginous
what m can open the auditory tube
tensor veli palatini
What are the auditory ossicles
malleus, incus and stapes
where is the malleus and what does it do
contacts TM making jumbo
vibrates in response to movement of TM
where is the incus
body articulates with head of malleus
long limb articulates with stapes
where is the stapes and what does it do
the base contacts oval window
vibrations of stapes induced motion of fluid in cochlear duct
What are the mm of the middle ear
stapedius and tensor tympani
o i inn aciton stapedius
o: posterior wall of tympanic cavity (pyramidal eminence)
i: stapes
VII SVE
dampens movement of ossicles
o i inn action tensor tympani
o: cartilaginous part of pharyngotympanic tube
i: malleus
V3 SVE
dampens movements of ossicles
what can cause hyperacusis (excessive hearing acuteness)
paralysis of middle ear mm due to loss of dampening
what aa supply middle ear
infeiror tympanic from ascending pharyngeal
anterior tympanic from maxillary
posterior tympanic from stylomastoid
superior tympanic from middle meningeal
a of pterygoid canal from tubal branches to pharyngotympanic tube
where do vv drain middle ear
pterygoid plexus
What n supplies GVA GVE-P to middle ear and part of auditory tube
IX, tympanic branch which forms a tympanic plexus on promontory of tympanic cavity
the lesser petrosal n coming from tympanic plexus has what info
GVE-P for parotid gland
what does CN VII inn in ear
stapedius SVE
what branch is given off VII before it exits middle ear
chorda tympani
What is otitis media
inflammation of middle ear that is caused by infection from pharynx that traveled in auditory tube
What are the tympanic cavity and auditory tube dervied from
1st pharyngeal pouch
what are the malleus, incus and tensor tympani m derived from
1st pharyngeal arch
what arch are the stapes and stapedius m derived from
second
congenital fixation of stapes can lead to what
deafness
Where is the internal ear and what is in it
in petrous portion of temporal bone
houses the vestibulocochlear organ
what is the bony labyrinth of internal ear
bassage within temporal bone filled with perilymph
what is the modiolus of cochlea
central bony core which cochlea spirals 2.5 times
what is the spiral ligament of the bony labyrinth of internal ear
anchors cochlear duct to bondy wall of cochlea
what is the osseous spiral lamina of the cochlea
anchors cochlear duct to modiolus
what is the vestibule of the bony labyrinth
has utricle and saccule
also has vestibular aqueduct which opens near internal acoustic meatus
What are the portions of the bony labyrinth of internal ear
cochlea
vestibule
semicircular ducts
What is the membranous labyrinth
membranous ducts contained in bony part, filled with endolymph
all portions of membranous labyrinth are inn by what
VIII
what are the componenets of the membranous labyrinth
endolymphatic duct utricle saccule semicircular ducts cochlear duct
what is the endolymphatic duct
passes thru vestibular aqueduct and ends as endolymphatic sac
maintains volume and composition of endolymphatic fluid
what is the function of utricle
responds to horizontal acceleration
what is the function of saccule
responds to changes in vertical acceleration
what is the function of semicircular ducts
respond to rotation of head
what is the organ of hearing
cochlear duct
what are the components of the cochlear duct
vestibular membrane- roof
basilar membrane- floor
spiral organ (organ corti)- hair cells and tectorial membrane
what does the vestibular membrane of cochlear duct separate
cochlear duct from scala vestibuli
what does the basilar membrane of cochlear duct separate
cochlear duct from scala tympani
What does the vestibular portion of VIII inn
utricle, saccule, semicircular ducts
what does the cochlear portion of VIII inn
cochlear duct to carry info about sound to brainstem
what is the membranous labyrinth derived from
otic placode (ectoderm) to otic pit to otic vesicle
what is the bony labyrinth derived from
surrounding mesenchyme