Clinical Anatomy of the Ear Flashcards
what bone houses the mechanisms for hearing and balance?
temporal
what are the two parts of the external ear?
pinna
external acoustic meatus
what marks the medial end of the external acoustic meatus?
the tympanic membrane
what forms the pinna?
elastic cartilage attached to the temporal bone, encased in skin
which part of the EAM is formed by cartilage?
the lateral third
what is the EAM lined with?
skin continuous with the pinna, containing ceruminous glands
what do ceruminous glands produce?
earwax
what are the two parts of the temporal bone?
squamous
petrous
what supplies the sensory nerve supply to the inferior part of the EAM and tympanic membrane?
CN X
what supplies the sensory nerve supply to the superior parts of the EAM and most of the tympanic membrane?
CN V3 via the auriculotemporal nerve
what supplies the sensory nerve supply to the superior portion of the helix?
C2 and C3 spinal nerves via the lesser occipital nerves
what supplies the sensory nerve supply to the earlobe?
C2 and C3 spinal nerves via greater auricular nerve
what is used to examine the EAM and tympanic membrane?
an otoscope
what is the thin part of the tympanic membrane called?
pars flaccida
what is the most inwardly depressed part of the tympanic membrane called?
the umbo
what is the thick part of the tympanic membrane called?
pars tensa
where is the cone of light normally directed in otoscopy?
anteroinferiorly
what are the first bones to fully ossify during development?
the ossicles
what is the function of the ossicles?
convey vibrations of the tympanic membrane due to sound and conduct them to the inner ear
from lateral to medial, what are the ossicles?
malleus
incus
stapes
what forms the connections between the ossicles and what does this allow?
small synovial joints
smooth movements between the bones
how are the ossicles suspended in the tympanic cavity?
by small ligaments and mucosal folds
these carry small vessels and nerves that supply the ossicles
what are the two muscles found in the tympanic cavity?
tensor tympani
stapedius
where does tensor tympani insert?
malleus
what innervates tensor tympani?
CN V3
where does stapedius insert?
stapes
what innervates stapedius?
CN VII
where is the tympanic cavity located and what does it contain?
the petrous portion of the temporal bone
contains the apparatus for the middle ear
what are the two parts of the tympanic cavity?
tympanic cavity proper
epitympanic recess
what nerve supplies the mucosa of the middle ear?
glossopharyngeal nerve
CN IX
where is the epitympanic recess found?
superior to the tympanic membrane
what is the opening in the posterior wall of the epitympanic recess called?
the mastoid aditus
opens into the mastoid air cells
what is the roof of the tympanic cavity called?
tegmen tympani
what separates the tympanic cavity from the middle cranial fossa?
roof of the tympanic cavity
what vessel is closely related to the floor of the tympanic cavity?
the internal jugular vein
what are the four key features of the medial wall of the tympanic cavity?
oval window
round window
promontory
facial canal
what does the oval window do?
receives the footplate of the stapes
what does the round window do?
dissipates forces from the cochlear
what is the promontory?
the bump from the basal (first) turn of the cochlear
what does the facial canal contain?
the facial nerve (CN VII)
what is the connection between the middle ear and the nasopharynx called?
the eustachian tube
where is the opening for the eustachian tube found in the nasopharynx?
posterior to the inferior nasal concha
what forms the eustachian tube?
posterior third = bone
rest = cartilage
what is the role of the eustachian tube?
equalise air pressure between the middle ear and the nasopharynx
what is the torus tubarius?
a feature of the nasopharynx caused by the cartilaginous opening of the eustachian tube
what is the mucosa of the nasal cavity continuous with and how?
the mucosa of the middle ear
via the eustachian tube
where can pain from inflammation of the tonsils/pharynx be referred to?
the ear, causing otalgia
where is the inner ear located?
deep within the petrous portion of the temporal bone
what are the two main structures of the inner ear?
bony labyrinth
membranous labyrinth
what is the bony labyrinth?
a fluid filled network in the otic capsule
what is the membranous labyrinth?
a series of communicating ducts and sacs suspended in the bony labyrinth
what parts of the inner ear are involved in hearing?
cochlear
what parts of the inner ear are involved in balance?
semi-circular canals
utricle
saccule
what are the three parts of the bony labyrinth?
cochlear
vestibule
semi-circular canals
what is the cochlear?
a shell shaped spiral cavity encircling a bony core
contains the round window
what is the bony core of the cochlear called?
the modiolus
what is the vestibule and what does it contain?
a small oval shaped chamber containing the utricle and saccule
contains the oval window
what are the vestibular organs?
utricle and saccule
what are the semi-circular canals?
three bony canals that communicate with the vestibule
are oriented at right angles to each other
what suspends the membranous labyrinth in the bony labyrinth?
spiral ligament
delicate filaments
which two semi-circular canals have a shared stalk?
posterior and anterior ducts
what are the three semi-circular ducts?
anterior
lateral
posterior
what achieves conversion of mechanical to neural stimuli in the inner ear?
specialised mechanoreceptors called hair cells
where are the hair cells within the vestibular apparatus located?
maculae of the utricle and saccule
ampullae of the semi-circular ducts
how do the neural stimuli generated by hair cells reach the CNS?
via the vestibular nerve
a division of CN VIII
where are the cell bodies for the neurons of the vestibular nerve located?
within the vestibular ganglion
what are the three fluid filled channels that make up the cochlear?
scala vestibuli
scala tympani
cochlear duct/scala media
what is the apex of the cochlear called and what ducts meet here?
helicotrema
scala vestibuli and tympani
where are hair cells located in the cochlear apparatus?
the organ of corti
how do neural stimuli travel from hair cells of the cochlea to the CNS?
the cochlear nerve
where are the cell bodies of the cochlear nerve located?
the spiral ganglion