Ear Flashcards
what are the contents of the external ear?
auricle
external auditory meatus
external surface of tympanic membrane
what are the contents of the middle ear?
internal surface of tympanic membrane
tympanic cavity
ossicles
pharyngotympanic (eustacian) tube
what are the contents of the inner ear?
auditory and vestibular apparatus internal auditory meatus vestibulocochlear nerve (CN VIII) oval and round windows
what type of cartilage forms the auricle?
elastic cartilage
what provides lymphatic drainage of the auricle?
parotid and cervical nodes
what gives arterial supply to the auricle?
posterior auricular
anterior auricular
superficial temporal
…and their perforating branches (all from ECA)
what innervates the auricle of the ear?
CN VII, IX and X (facial, vestibulocochlear or vagus)
auriculotemporal (CN V3)
lesser occiptal and great auricular (from cervical plexus)
what forms the lateral 1/3rd and medial 2/3rds of the external auditory meatus?
lateral 1/3rd: elastic cartilage, hair follicles, sweat and sebaceous glands
medial 2/3rds: bone lined with stratified squamous epithelium
what innervates and gives arterial supply to the external auditory meatus?
blood: auricular branches of ECA
innervation: auriculo-temporal (CN V3), auricular branches form CN VIII and X
what shape and size is the tympanic membrane?
roughly circular
8mm diameter
what lines the medial and lateral layers of the tympanic membrane?
medial: mucous membrane
lateral: stratified squamous
what runs across the medial surface of the tympanic membrane and what attaches to it?
across: chorda tympani
attaches: malleus
what innervates the lateral and medial surfaces of the tympanic membrane?
lateral: auriculotemporal (CN V3) and auricular branch of CN X
medial: tympanic branches of CN IX
what muscles are present in the tympanic cavity of the middle ear and what is their combined function?
tensor tympani and stapedius
reduce vibration passing to inner ear
where is tensor tympani and what is it’s function?
wall of auditory tube –> handle of malleus
function: tense tympanic membrane
what innervates tensor tympani?
CN V3
where is stapedius and what is it’s function?
pyramid of middle ear –> neck of stapes
pull ‘footplate’ of stapes laterally
what innervates stapedius?
CN VII
what gives sensory supply to the tympanic cavity (incl. medial surface of tympanic membrane)?
CN IX
what supplies blood to the tympanic cavity?
tympanic branches of posterior auricular, ascending pharyngeal and maxillary arteries
what is the route of the chorda tympani?
crosses medial surface of tympanic membrane and handle of malleus
exits tympanic cavity via petrotympanic fissure
joins lingual nerve
what does the chorda tympani supply?
parasympathetic: sublingual and submandibular salivary glands
taste: anterior 2/3rds tongue
what does the pharyngotympanic tube connect?
nasopharynx and tympanic cavity
what is the pharyngotympanic tube formed of and lined with?
lateral (1.2cm): bony canal lined with mucosa
medial (2.5cm): cartilaginous and membranous
the auditory tube is normally closed but the contraction of what muscle causes the lumen to open?
tensor veli palatini (i.e. when swallowing, yawning etc.)
what is the role of the pharyngotympanic tube?
equalising pressure on both sides of the tympanic membrane
what innervates the pharyngotympanic tube?
sensory from CN IX
what supplies blood to the middle ear?
anterior tympanic (glaserian) artery from 1st part of maxillary artery also from ascending pharyngeal (inferior tympanic), middle meningeal (superior tympanic), posterior auricular (stylomastoid, posterior tympanic), artery of the pterygoid canal and caroticotympanic branch of the ICA
what is the role of perilymph and endolymph?
conduct sound vibration and respond to mechanical forces (movement and acceleration)
what is found in the bony labyrinth and what is it?
contains cochlea, vestibule and semicircular canals
system of canals filled with perilymph
what surrounds the bony labyrinth?
otic capsule
very dense bone within the petrous temporal bone
what is the membranous labyrinth?
continuous system of ducts and sacs inside the bony labyrinth
suspended in perilymph but contains endolymph
where are the semicircular canals?
posterior and lateral to the vestibule
what are the names given to the canals and what are the positions of each relative to one another?
anterior, posterior and lateral
anterior and posterior are at right angles, lateral is horizontal
what do the semicircular canals contain and what are the names given to the swellings at the end?
contains the semi-circular ducts
swellings = ampullae
what does each ampullae contain and what is their function?
equilibrium receptors called crista ampullaris
respond to rotational movements of the head
what is the vestibule and what does it contain?
bony labrynth, 5mm long
contain two membranous sacs - the utricle and saccule
what house the maculae and what do they respond to?
the utricle and sacule house the maculae
respond to pull of gravity and chages in the head position due to the presence of otoliths (calcium carbonate crystals that respond to gravity)
what innervates the cochlea?
spiral (cochlear) ganglion from the cochlear nerve from CN VIII
what innervates the utricle, saccule, semicircular duct and vestibule?
axons of the vestibular ganglion from the vestibular nerve from CN VIII
what gives arterial supply to the inner ear?
Internal auditory branches (labyrinthine, form the cochlear and vestibular arteries arising as a branch of the anterioinferior cerebrallar artery (80%) or basilar artery (20%))