Anatomy: Ear Flashcards
petrous part of temporal bone
zygomatic process of temporal bone
arises from squamous part and articulates wihth zygomatic bone
pterion
frontal, parietal, temporal and sphenoid bones
thinnest part of the skull
which part of the temporal bone is the mastoid process found on
petrous part
which bones form the anterior cranial fossa
frontal, ethmoid and sphenoid
which bones form the middle cranial fossa
sphenoid and temporal
which bones form the posterior cranial fossa
temporal and occipital
C O S F F I J H
order of cranial foraminae
“Carlos only smokes spliff since Rastaman offered skunk in indigenous Jamaica. Jamaican joint heaven”
COSFFIJH
external ear
from auricle to tympanic membrnae via external acoustic meatus
collect and convey sound waves to tympanic membrane
middle ear
from tympanic membrane to oval window and esutachian (auditory) tube
amplifies and conducts sound waves to internal ear
internal ear
from oval window to internal acoustic meatus
converts special sensory information - into fluid waves, then APs which are conducted to the brain
auricle anatomy
describe the innervation of the skin of the external ear
tympanic membrane and EAM sensory nerve supply
CNV3 (superior part of EAM and tympanic membrane) and CNX (inferior part of EAM and TM)
what is the lymphatic drainage of the lateral surface of the superior half of the auricle
parotid lymph nodes
what is the lymphatic drainage of the cranial surface of the superior half of the auricle
mastoid lymph nodes (purple) and deep cervical (light green)
what is the lymphatic drainage of the rest of the auricle, including the lobe
superficial cervical lymph nodes (dark green)
where does all lymph from the auricle eventually drain to
deep cervical lymph nodes (in carotid sheath), thoracic duct and then venous angle
what forms the skeleton of the external ear
temporal bone
is the elastic cartilage of the ear vascularised?
no - gets nutrients from the skin
where does the EAM extend from
deeper part of concha to tympanic membrane
structure and support of EAM walls
given structure from cartilage and bony support from temporal bone
what glands does the EAM produce earwax via
ceruminous glands
what does otoscopic examination involve
examination of the EAM and tympanic membrane, the EAM must be straight
compare a child’s EAM to that of an adults
a child’s is short and straight - pull posterioinferiorly (and be careful not to damage tympanic membrane)
curved in an adult - pull posteriosuperiorly
umbo = most inwardly depressed part of tympanic membrane (handle of malleus)
pars flaccida = superiorly thin part of tympanic membrane
pars tensa = thickest part of tympanic membrane (posteroinferiorly)
describe the innervation of the tympanic membrane
external surface: mainly CNV3 (auriculotemporal branch)
internal surface: CNIX
eustachian (auditory) tube
connects the tympanic cavity to the lateral wall of the nasopharynx
CNIX sensory innervation
middle ear cavity
eustachian tube
naso and oro pharynx
tonsils
what are the 3 bones of the middle ear called
auditory ossicles
they link the tympanic membrane to the oval window of the internal ear
how do the auditory ossicles articulate
via synovial joints
which part of the stapes bone joints the oval window
base
which bone creates the umbo
the handle of the malleus - adheres to the internal aspect of the tympanic membrane
what is the function of the auditory tube
connects middle ear cavity to nasopharynx
acts to equalise pressure of the middle ear to that of the EAM
which nerve runs over the internal aspect of the tympanic membrane
chorda tympani
- runs over handle of malleus
what is the clinical impact of the eustachian tube and infection
bacteria/viruses can spread between the middle ear cavity and nasopharynx
eg infection from pharynx/tonsils can cause pain and hearing loss
give an example of referred pain with CNIX
CNIX supplies: middle ear cavity, eustachian tube, nasopharynx, oropharynx, tonsils
tonsillitis or pharyngitis can mimic earache
mastoid process of temporal bone
how does the mastoid antrum communicate with the middle ear
via the aditus
the antrum contains the mastoid air cells in the mastoid process of the temporal bone
how does mastoiditis occur
it is inflammation of the mucosal lining of the mastoid antrum and mastoid air system inside the mastoid process
spread of infection through aditus from middle ear cavity
what forms the roof of the middle ear cavity
the petrous part of the temporal bone
note the middle cranial fossa
where does CNVII exit the cranial cavity
enters internal acoustic meatus on temporal bone
then enters facial canal on petrous temporal bone
exits facial canal via stylomastoid foramen - opening on surface of petrous part of temporal bone
stylomastoid forman in petrous part of temporal bone
what does the chorda tympani branch of CNVII supply
taste buds of anterior 2/3 rd of tongue
parasympathetic supply to submandibular and sublingual salivary glands
what does the facial canal on the petrous temporal bone connect
IAM and stylomastoid foramen
which muscle controls the stapes
the right/left stapedius (innervated by CNVII)
reduces the movement of the stapes to protect the internal ear from excessive noise
describe the innervation of the tongue
anterior 2/3:
- taste - chorda tympani CNVII
- general sensory - CNV3
posterior 1/3: CNIX
vermillion border
edge of lips
buccal fat pad
- what happens to it during illness
its loss in illness gives the appearance of sunken cheeks
it is a clinical sign of malnutrition
where do facial muscles originate and insert
originate on bone, insert into superficial fascia
how can muscles of facial expression and motor CNVII be tested
asking patient to: frown, close eyes tightly, smile , puff out cheeks
what are the 2 main functions of the inner ear
To convert mechanical signals from the middle ear into electrical signals, which can transfer information to the auditory pathway in the brain.
To maintain balance by detecting position and motion.
what are the 2 components of CNVIII
cochlear nerve - hearing
vestibular nerve - balance
where is the inner ear located
from oval window to internal acoustic meatus
petrous part of temporal bone
bony labryinth
- contents
also called otic capsule
bony cavities inside the petrous part of the temporal bone
it is composed of the cochlea, vestibule and 3 semicircular canals
what does the bony labryinth contain
it is lined by periosteum and contains perilymph fluid
membranous labryinth
inside the bony labryinth - suspended in the perilymph
it contains the cochlear duct, semicircular ducts, urticle and saccule
contains endolymph fluid
where are the saccule and urticle of the membranous labryinth located
within the vestibule of the bony labryinth - innervated by vestibular nerve
cochlear duct function
conducts APs to the brain stem via the cochlear nerve - auditory part of the ear
semicircular ducts
conduct APs to brainstem via vestibular nerve
describe the transmission of sound through the ear
where does CNVIII exit the cranial cavity
internal acoustic meatus
where do CNVII and CNVIII connect with the brain stem
at the junction between the pons and the medulla
describe the course of CNVI in the cranial cavity, and what this makes it susceptible to
leaves the brainstem at the pons
runs up and over petrous temporal bone
superior orbital fissure
Raised ICP can stretch the nerve and hinder its function causing a CNVI palsy. This is called a false localising sign
