Ear anatomy and embryology Flashcards
what is the function of the auricle?
collect airwaves and funnel them into external acoustic meatus.
what is the auricle made up of (structure)
cartilages
depressions (concha and schaphoid)
lobule –> composed of fibroelastic tissue
what is the blood supply to the auricle
posterior auricle artery and vein
superficial temporal artery and vein
what is the innervation to the auricle
greater auricular (C2, C3) and lesser occipital
auriculotemporal
facial n
vagus n.
what is the lymphatic drainage of the auricle
mastoid, parotid lymph nodes –> deep cervical
what is the external acoustic meatus
what bone is it in
what is it lined with
what is the lateral 1/3 and the medial 2/3 made up of
- Canal traveling through tympanic portion of temporal bone to tympanic membrane.
- Canal traveling through tympanic portion of temporal bone to tympanic membrane.
- Lined by stratified squamous epithelium containing numerous ceruminous glands.
- Lateral 1/3 is cartilaginous; medial 2/3 is bony
what is the blood supply to the external acoustic meatus (3)
a. Posterior auricular a. and v.
b. Superficial temporal a. and v.
c. Deep auricular a
what is the innervation of the external acoustic meatus
auricular temporal nerve (V3)
vagus n.
what is the lymphatic drainage of the external acoustic meatus
deep cervical lymph nodes
what is otitis external
inflammation of the external ear
what is the tympanic membrane attached to
handle of malleus
what is the function of the tympanic membrane
convert sound waves into vibrations of middle ear ossicles.
what does the tympanic membrane separate?
what is it covered with externally
and what covers it internally
which direction is the TM directed
a. Semitransparent, fibroelastic membrane
b. Separates external and middle ear.
c. Covered by epidermis externally; mucus membrane internally.
d. The membrane is directed anteriorly and inferiorly.
what is the umbo
central concavity of the TM
what is the pars flaccida and pars tensa
b. Pars flaccida – superior, thin-walled portion
c. Pars tensa – inferior, thick-walled portion
what is the blood supply to external TM
what is the innervation to the external TM
blood–> deep auricular branch of maxillary
GSA –> auriculotemporal nerve
Vagus n.
what is the blood supply to the internal TM?
what is the innervation to the internal TM
blood_–> anterior tympanic off maxillary
innervation–> GVA tympanic branch of glossopharyngeal
why is the TM a source of the cough reflex?
b/c of CN V being touched on the external surface of the TM
what arches is the auricle derived from
first and second pharyngeal arches.
6 auricular hillocks will later fuse to form the definitive auricle
defects of the auricle are commonly associated with what else?
chromosomal syndromes
what is the external auditory meatus formed from
what is the meatal plug and what is its fate
what is a clinical correlation of the meatal plug
first pharyngeal cleft
b. Meatal plug forms from proliferation of epithelial cells; by 7th month degenerates.
c. CLINICAL CORRELATION: Persistence of meatal plug can cause deafness.
external epithelium of tympanic membrane is derived from what
ectoderm of first pharyngeal cleft
middle CT of TM is derived from what
mesoderm of first pharyngeal arch
internal epithelium of TM is derived from what
endoderm of the first pharyngeal POUCH
what is in the middle ear
tympanic cavity–> mucous membrane-lined space within portion of the temporal bone and auditory ossicles
what is the function of the middle ear
- Transfer of sound waves from gas to liquid medium (from external to internal ear).
- Amplification of sound waves via vibration of bony ossicles.
- Protective response to loud sounds (via tensor tympani & stapedius mm).
what is the roof of the tympanic cavity
what does it separate
tegmen tympani –> separates epitympanic recess from middle cranial fossa
floor of tympanic cavity
what does it separate
segment of temporal bone separating middle ear from internal jugular vein
what is the lateral wall of the tympanic cavity
tympanic membrane
what is the medial wall of the tympanic cavity
what are the components
bony wall separating middle from internal ear
promontory
oval window
round window
what is the promontory
mound of bone created by cochlea
what is the oval window
fenestra vestibule
superior to the round window
opens to vestibule of internal ear
contacted by the stapes
transmits motion of stapes to fluid of internal ear
what is the round window (fenestra cochlea)
opens to scala tympani
covered with a thin membrane
acts as a pressure release valve for fluids of the internal ear
what is the aditus ad antrum
entrance to the mastoid antrum
what is the posterior wall of the tympanic cavity
temporal bone
aditus ad antrum
facial canal
what is mastoiditis
and why is it clincally significant
middle ear infections can sometimes spread to the mastoid air cells via the aditus ad antrum (opening to these air cells)
what is the anterior wall of the tympanic cavity
what openings are in it
segment of temporal bone separating middle ear from carotid canal
opening for pharyngotympanic tube (aka auditory tube) and semi-canal (passage of tensor tympani).
what is the pharyngotympanic tube
what is it lined by what does it connect what is its function posterolateral third is made by what anteromedial 2/3s
what muscle can open this tube and what is its innervation
auditory tube
- Mucous-membrane lined tube connecting middle ear and nasopharynx.
- Function – balances pressure on external and internal sides of tympanic membrane.
- Posterolateral third is bony; anteromedial 2/3 is cartilaginous.
- Tensor veli palatini muscle can open the membranous tube (CN V3
what are the auditory ossicles
malleus
incus
stapes
malleus
contacts TM
creates umbo
vibrates in response to movment of the TM
incus
body articulates with head of malleus
long limb articulates with stapes
stapes
base–> contacts oval window
vibration of stapes induces motion of the fluid within the cochlear duct
what are the 2 muscles of the middle ear
stapedius
tensory tympani
stapedius
attachments
function
innervation
a. Origin – posterior wall of tympanic cavity (pyramidal eminence)
b. Insertion – stapes
c. Function – dampens movements of ossicles
d. Innervation – facial nerve (CN VII; SVE)
tensor tympani
attachments
function
innervation
a. Origin – cartilaginous part of pharyngotympanic tube
b. Insertion – malleus
c. Function – dampens movements of ossicles
d. Innervation – trigeminal nerve (V3; SVE)
contracts when we are chewing or speaking
what is the cause of hyperacusis
paralysis of middle ear muscles can can this
excessive hearing acuteness due to loss of dampening
what is the blood supply to the middle ear? *5
veins?
- Inferior tympanic a (from ascending pharyngeal a)
- Anterior tympanic a ( 2nd branch from maxillary a)
- Posterior tympanic a (from stylomastoid a.)
- Superior tympanic (from middle meningeal a.)
- Artery of pterygoid canal (tubal branches to pharyngotympanic tube).
- Venous drainage to ptergyoid plexus
what type of joints are the ossicles?
synovial
as we age they can undergo oto sclerosis and these can fuse! so we have shit hearing
what are the two nerves of the middle ear?
CN IX
CN VII
what are the three branches given off by CN VII
nerve to stapedius (SVE) greater petrosal (GVE-P ) chorda tympani (SVA and GVE-P)
what are the branches given off by CN IX in the middle ear?
tympanic branch (GVA, GVE-P)
turns into lesser petrosal –> parotid gland
otitis media
inflammation of the middle ear–> often due to spread of infection from pharynx via pharyngo tympanic tube
what are the tympanic cavity and the auditory derived from
first pharyngeal pouch
malleus, incus and tensor tympani are derived from what
first pharyngeal arch
stapes and stapedius muscle are derived from wha
2nd pharyngeal arch
what is clinically significant about the stapes and its connection to the oval window
if it becomes congenitally ossified then deafness will ensue
conductive hearing loss
where is the internal ear?
what does it contain
housed in the petrous portion of the temporal bone
internal ear contains the vestibulocochlear organ involved in balance and hearing
what is inside the bony labyrinth
perilymph
cochlea
vestibule
semicircular canals
what is inside the membranous labyrinth
endolymph
all portions innervated by CN VIII
what is the endolymphatic duct
maintains the volume and composition of endolymphatic fluid
must have high K concentration
what is the cochlear duct
organ of hearing
vestibular membrane- roof
basilar membrane - floor
spiral organ of corti - hair cells
what are the two components of the vestibulocochlear nerve (CNVIII)
- Vestibular portion innervates semicircular ducts, utricle, and saccule to carry proprioceptive information (movements of the head) to the brain.
- Cochlear portion innervates cochlear duct to carry information about sound to the brainstem (spiral organ)
what is the membranous labyrinth derived form
otic placode –> otic sac–> otic vesicle
what is the path of production of sound
- Airways travel down external acoustic meatus causing vibration of tympanic membrane.
- Motion of the tympanic membrane causes vibration of the three middle ear ossicles.
- Footplate of stapes contacts oval window and causes movement of the fluid in the inner ear.
- Movement of fluid in the cochlear duct causes bending of the hair cells imbedded within the spiral organ.
- Bending of these hair cells initiates signaling events which ultimately lead to propagation of a nerve impulse along the cochlear portion of CN VIII.
what is bony labyrinth derived from?
surrounding mesenchyme (vestibule, semicirucular canals, cochlea)
