Anatomy- The ear Flashcards
what bounds the external ear
pinna
what is the pinna formed from
neural crest cells
what are the functions of the ear
hearing (auditory system, cochlear)
balance (vestibular system, semicircular canals)
which bone holds all the parts of the ear
temporal
what nerves exist in the temporal bone
CN VIII (vesticulococclear) (stays in bone) and CN VII (facial) (passes through bone)
what is the pterion
H shaped structure where frontal, parietal, temporal and sphenoid bones join
thinnest part of the skull
what forms the squamous part of the temporal bone
1st pharyngeal arch from the neural crest
what do the digastric muscle attach to
styloid process
what bone can infection of the middle ear blow out
mastoid process
what does the styloid process form from
2nd arch
what forms the zygomatic arch
zygomatic process of the temporal bone
what can rupture of the pterion cause
epidural haematoma
were does the facial nerve exit the temporal bone
stylomastoid foramen
what nerves could a pathology in the internal accoustic meatus develop
CNs VII and VIII
what nerves come out of the jugular foramen
CN 9, 10 and 11
what are the roles of the facial nerve
motor to face motor to stapedius taste to anterior 2/3rds of tongue secretomotor to salivary glands and lacrimal gland general sensation to external ear
what is the role of the vestibulocochlear nerve
balance
hearing
what is the labyrinthine artery
branch of anterior inferior cerebellar artery from circle of willis
what is in the internal accoustic meatus
CN VII, CN VIII, labyrinthine artery and vein
what is the circle of willis
blood supply to the brain and brain stem
everything supplied by the facial nerve is from what pharyngeal arch
2nd
what makes up the external ear
the auricle to the tympanic membrane (via the external acoustic meatus)
what is the role of the external ear
collects and conveys sound waves to the tympanic membrane
what makes up the middle ear
tympanic membrane to oval window + eustachian tube (aka auditory tube, pharyngotympanic tube)
what is the role of the middle ear
amplifies and conducts sound waves to the internal ear
what makes up the internal ear
oval window to the internal acoustic meatus
what is the role of the internal ear
converts special sensory information into fluid waves, then APs
then conducts APs to the brain
what covers the oval window
the stapes (an ossicle)
what does the eustachian tube do
connects the tympanic cavity (middle ear) to the lateral wall of the nasopharynx
what does the ear cartilage form from
neural crest cells
is the external ear vascular
no gets nutrients from the skin
what type of cartilage in the external ear
elastic
where does the ear canal begin
at the external accoustic meatus
what makes up the ear canal
1/3rd cartilage 2/3rds bone
lined with skin
what does the ear canal produce
ear wax via ceruminous glands
what is the nerve supply to the external ear
outer half= C2,3 spinal nerves and CN VII
superior parts of EAM and most of the tympanic membrane= CN V3
inferior parts of EAM and tympanic membrane = vagus
facial nerve also does sensation (one of few areas where is does) around the concha of the auricle
what is the tragus
external convering of external acoustic meatus
where does the lymph from the lateral surface of the superior half of the auricle drain to (infront of the ear)
parotid
where does the lymph from the cranial surface of superior half (behind the ear)
mastoid lymph nodes (and deep cervical)
where does most of the auricle including the lobe drain its lymph to
superficial cervical lymph nodes
where does all lymph from auricle eventually drain to
deep cervical lymph nodes (in carotid sheath) then thoracic duct/ right lymphatic duct at venous angles
what is the EAM like in children - what does this mean for an otoscopic exams
short and straight
be careful not to damage the tympanic membrane when pulling auricle posteroinferiorly
how and what do you exam in an otoscopic exam
EAM and tympanic membrane
straighten EAM (n adults this is curved)
gently pull auricle posterosuperiorly
what is the umbo
the most inwardly depressed part of the tympanic membrane
where is the cone of light normally
directly anteroinferiorly
what is the pars tensa
the thick part of the tympanic membrane - posteroinferiorly
what is the cone of light a good indicator of
that the part flaccida and pars tensa are in the correct places
what is the nerve supply to the tympanic membrane
external surface- mostly CNV3 (auriculotemporal nerve)
internal surface CN IX
what does the glossopharyngeal nerve (CN IX) provide sensory innervation to
middle ear cavity eustachian tube nasopharynx oropharynx tonsils
what three bones are in the middle ear
malleous
incus
stapes
what 2 muscles are in the middle ear
stapedius (facial nerve) tensor tympani (V3)
what nerves exist in the middle ear
facial nerve
glossopharyngeal
where is the epitympanic recess
superior to the tympanic membrane
how do auditory ossicles articulate
synovial joints
what creates the umbo
handle of the malleus which is adherent to the internal aspect of the tympanic membrane
where do the footplates of the stapes fit into
the oval window
what is the mastoid antrum
air filled space in the petrous portion of the temporal bone
what is the mastoid process
back part of temporal bone
what is the chorda tympani and its role
branch of the facial nerve
travels through the middle ear between the malleus and incus
carries afferent special sensation from the anterior 2/3rds of the tongue
and parasympathetic secretomotor innervation to the submandibular and sublingual glands
what innervates the tensor tympani muscle
V3
what innervates the stapedius muscle
CN VII
what is the aditus
‘doorway’ into the mastoid antrum from the epitympanic recess
what can cause mastoiditis
(inflammation of the mastoid process)
spread of infection from the middle ear cavity
what is the ear drum
the tympanic membrane
what forms the bone prominence on the medial wall of the tympanic cavity
lateral semicircular canal
cochlear
where is the middle ear (tympanic cavity)
in the petrous temporal bone
what is the middle ear
in tympanic cavity p- from tympanic membrane to the lateral wall of the inner ear
what is the mastoid
portion of temporal bone which contain air filled spaced
what are the auditory and pharyngotympanic tubes
other names for the eustachian tube
what does the eustachian tube do
connects the anterior wall of the middle ear cavity to the nasopharynx
what is the nerve supply to the eustachian tube
CN IX
why tonsilitis can mimic earache
what is the sensory innervation to the laryngopharynx
mostly from vagus
what is the adenoid
the pharyngeal tonsil- a mass of enlarged lymphatic tissue between the back of the nose and the throat
why is otitis media (infection of the middle ear) more common in children
as eustachian tube open and short- easier for bacteria/ viruses to spread
what is the mixed media of the facial nerve
has four axon types
- special sensory
- sensory
- motor
- parasympathetic
what is the path of the facial nerve
connects to brain stem at pontomedullary junction goes into internal accoustic meatus goes through facial canal gives off chorda tympani branch comes out stylomastoid foramen supplies muscles of facial expression
what is the role of the facial nerve
motor- muscles of facial expression, digastric, stylohoid, stapedius muscles
sensory- around concha of the auricle
special sensory- taste to anterior 2/3rds of the tongue
parasympathetic- submandibular, sublingual glands, nasal, palatine and pharyngeal mucous glands, lacrimal glands
what is the role of the stapedius
reduces stapes movement to protect the internal ear from excessive noise
what does the chorda tympani go on to connect to
lingual nerve (branch of CN V3)
where does CN V3 leave the base of the skull
foramen ovale
what supplies the sublingual salivary gland
CN VII
where do the muscles of facial expression originate and insert
originate on bone, insert into superficial fascia
how do you test the muscles of facial expression (and therefore motor function of CN VII)
frown- frontalis
close eyes tightly- orbicularis oculi
smile- elevators
maintain puffed out cheeks (can hold in air when you tap cheeks)- orbicularis oris
what gives the appearance of sunken cheeks
loss of the buccal fat pad
what is the vermillion border
border of the lips
where is the inner ear
in petrous part of the temporal bone
what are the two parts of CN VIII
vestibulocochlear
cochlear nerve- hearing
vestibular nerve- balance
what is in the otic capsule
bone labyrinth- fluid (perilymph) filled spaces
what is suspended within the perilymph of the bony labyrinth
membranous labyrinth- communicating sacs and ducts
contains endolymph fluid
how many semicircular canals are there and what are they called
3
superior
lateral
posterior
what is perilymph
fluid that fills the bony labyrinth- floats the membranous labyrinth
what is the cupula
the apex of the spinal (cochlear)
hoe many turns does the cochlear have
2.5
what does the perilymph communicate with
central nervous system
what is the cochlear duct
long balloon structure within the cochlear filled with endolymph
what conducts AP from the cochlear to the brain stem
the cochlear nerve
what are the semicircular ducts filled with
endolymph
what conducts APs from the semicircular ducts to the brainstem
the vestibular nerve
where is the cochlear nerve
in the cochlear duct
what is the organ of corti
receptor organ for hearing within the cochlear
what stimulates hair cells in the vestibular apparatus
movement of endolymph
what are maculae
regions of clusters of hair cells in the vestibular apparatus
what do the semicircular ducts detect
angular movement change
what do the utricle and saccule detect
linear movement changes
- utricle= horizontal
- saccule= vertical
describe the path of sound transmission within the inner ear
sound waves make the tympanic membrane vibrate
vibrations transmitted through ossicles
base of stapes vibrates in oval window
hair cells in the cochlear are moved
AP stimulated and conveyed to brain by cochlear nerve
pressure eaves descend and become vibrations again
pressure waves dampened at the round window
what is the function of the round window
to dissipate the forces created through the oval window
what in the cochlear detects auditory stimuli
receptor cells in the organ of corti
where is the organ of corti
basilar membrane of the cochlear duct
what suspends the cochlear duct
spiral ligament
what does the cochlear duct divide the cochlear canal into
scala vestibuli (sound in) scala tympani (sound out)
which nerves connect with the brainstem at the pontomedullary junction
CN VII and CN VIII
what is the pontomedullary junction between
pons and medulla oblongata
what is the path of CN VIII
two types of fibres join in the pons
exits the cranium via the internal acoustic meatus
splits to go to either cochlear (cochlear nerve axons) or vestibular aparatus (vestibular nerve axons)