Exam 4 Ear Flashcards
What is the ectodermal thickening on the lateral “head”
Placode
What does the placode give rise to
The auditory pit, then auditory vesicle
What does the auditory vesicle give rise to
Most of the membranous inner ear
What secondary embryologic feature is derived from the 1st pharyngeal pouch
The auditory tube and tympanic cavity
What is the malleus derived from
The dorsal end of the ventral mandibular cartilage
What is the incus developed from
The dorsal end of the first pharyngeal arch
What is the stapes derived from
The dorsal end of the second pharyngeal arch
What is the tympanic membrane developed from
Interstitial mesoderm
What is the external acoustic canal developed from
First pharyngeal groove
What is the auricle developed from
A groove next to the 1st pharyngeal groove
What are the 3 portions of the ear
External, middle, inner
What are the 2 features of the external ear
The auricle and external acoustic meatus
What is another name for the auricle of the external ear
Pinna
What is the function of the auricle
Funnel sound waves into external acoustic meatus
What are the 3 extrinsic muscles of the auricle
Anterior auricular muscle, superior auricular muscle, and posterior auricular muscle
What are the intrisic muscles of the auricle
Helicus major/minor, tragicus, antitragicus, transverse muscle of the auricle, oblique muscle of the auricle
What is the shape of the external acoustic meatus
S shaped
Where is the medial 2/3 of the external acoustic meatus
Within temporal bone
What glands are located in the external acoustic meatus
Modified sweat glands producing cerumen
Where does the external acoustic meatus terminate
At the tympanic membrane
How is blood supplied to the external ear
Posterior auricular branch, anterior auricular branch, auricular branch
What is the sensory supply to the external ear
Auriculotemporal nerve, auricular branch, great auricular nerve (C2 and C3)
What is the motor supply of the external ear
Temporal and posterior auricular branches
What is the sympathetic supply to the external ear
From superior cervical ganglion
Where is the middle ear
Small space between tympanic membrane and inner ear
What are the 2 parts of the middle ear
Tympanic cavity and epitympanic recess
What are the 3 small bones in the middle ear
Incus, malleus, stapes
What 2 muscles are located in the tympanic cavity
Stapedius and tensor tympani
What is the blood supply to the middle ear
Anterior tympanic branch and tympanic branch
What is the sensory supply of the middle ear
Tympanic nerve of CN IX (pregang parasymp)
What is the motor supply of the middle ear
Nerve to stapedius (CN VII) supplying stapedius, medial pterygoid nerve
What does the medial pterygoid nerve of mandibular division supply within the middle ear
Tympani muscle
What is the sympathetic supply of the middle ear
Carotympanic nerves carry vasomotor and secretomotor fibers from superior cervical ganglion by way of internal carotid plexus
What is another name for the inner ear
Labyrinth
What are the two parts to the labyrinth
Bony and membranous
What is the bony labyrinth an enclosure for
The membranous labryinth
What is the membranous labyrinth surrounded by
Surrounded by perilymph within the bony labyrinth
What are the 3 parts of the bony labyrinth
The cochlea, the vestibule, the semicircular canals
What is contained within the cochlea
The cochlear duct
Where is the utricle and saccule contained
The vestibule
What contains the semicircular ducts
The anterior/superior,lateral, posterior semicircular canals
What connects the utricle and saccule
Utricosaccular duct
Where is the endolymphatic duct located
From utricosaccular duct to just below the dura ending at the endolymphatic sac
What is a reservoir for endolymph
The endolymphatic sac
What connects the saccule with cochlear duct
The ductus reuniens
the bony part of the cochlear that consists of a tube coiled around a cone shaped central bony structure called what
The modiolus
How many times does the cochlea wrap around the modiolus
2.5-2.75 times
What is the apex of the cochlea
The cochlear capula directed anterolaterally
What is the bony ridge that connects the cochlea to the modiolus
The lamina of the modiolus
What are the 3 channels of the cochlea
Cochlear duct, scala vestibuli, and scala tympani
Where does the cochlear duct end
At the apex of the cochlea
The scala vestibuli and scala tympani communicate with each other at the apex through a channel called what
The helicotrema
Is the scala vestibuli filled with endolymph or perilymph
Filled with perilymph
What forms the base of the scala vestibuli and what is its purpose
The oval window forms the base so vibrations are transmitted into the scala vestibuli as the stapes vibrates
Where is the scala vestibuli located and where is the scala tympani located
Scala vestibuli = above cochlear duct, scala tympani = below the cochlear duct
Vibrations transmitted through the scala vestibuli pass to the scala tympani via what
The helicotrema
What is the base of the scala tympani
The round window
How is the cochlear duct anchored to the outer wall of the cochlea
By the spiral ligament
What separates the cochlear duct from the scala vestibuli
The vestibular membrane
What separates the scala tympani from the cochlear duct
The basilar/spiral membrane
Where is the spiral organ located
On the floor of the cochlear duct, attached to the basilar/spiral membrane
What part of the inner ear is sensitive to frequency and amplitude of sound waves that enter the cochlea
The spiral organ
What are the hair cells of the spiral organ covered by
The tectorial membrane
What information is conveyed by spiral organs
It is conveyed from receptor cells to primary sensory neurons, cells bodies for the neurons are in the spiral ganglion
After sound waves enter the external acoustic meatus what is impacted
The tympanic membrane vibrates
How does sound travel through the ossicles of the middle ear (i.e. the order of them)
Malleus, incus, stapes transmit the vibrations
How much is sound amplified by going through the ossicles of the middle ear
Amplifies the vibration 1.2 times
What does the foot of the stapes articulate with
The oval window forming the base of the scala vestibuli
Since the oval window is smaller than the tympanic membrane how much are the vibrations amplified
Another 17 times
After vibrations travel through the oval window where do they go
Transmitted through perilymph of scala vestibuli and scala tympani to the round window
What does the wave through the perilymph of the scala vestibuli/tympani through the round window then travels through perilymph causing what to vibrate
The basilar membrane
What does the vibration of the basilar membrane stimulate
Receptors in the spiral organ
After vibrations stimulate the receptors in the spiral organ where do they then go
The cochlear nerve
What are the two sacs of the vestibular labyrinth
The saccule and utricle along with 3 semicircular ducts
What fluid is contained within the structures of the vestibular labyrinth
Endolymph
What does the saccule of the vestibular labyrinth communicate with
The cochlear duct via the ductus reuniens
Which is larger the utricle or saccule and what does it communicate with
The utricle is larger and communicates with all 3 semicircular ducts
How does the utricle communicate with the saccule
The utricosaccular duct
What are the sense organs within the utricle and saccule called
Maculae
What part of the vestibular floats on the endolymph
Otoliths
What do movements of the head cause the otoliths to do
To deflect the maculae, eliciting impulses
What does the utricle detect
Centrifugal and linear accelerations (in all planes)
What does the saccule detect
Linear accelerations in vertical and A/P planes
What are the sense organs in the semicircular ducts called and where are they located
Crista located in the ampulla of each duct
What are the semicircular ducts sensitive to
Any direction but particularly sensitive to rotational accelerations
Impulses initiated by crista are carried by neurons with cell bodies located wehre
Vestibular ganglion
What are the branches of dendrites carrying info to the vestibular ganglion
Inferior and superior branches
How many fibers are carried in the sup/inferior dendritic branches to the vestibular ganglion
Sup = 12,000 and inf = 8,000
The superior branch of the vestibular ganglion carries info from where
The anterior and lateral semicircular duct and the utricle, also some from the saccule (Voit’s) nerve
The inferior branch of the vestibular ganglion carries info from where
The posterior semicircular duct and the saccule
Axons from the vestibular ganglion make up the what
Vestibular nerve
What is the blood supply of the labyrinth
Internal auditor artery, and the stylomastoid artery
What is the sympathetic nerve supply to the labyrinth
From the cavernous and/or internal carotid plexuses
The cochlear nerve is composed of axons that send information through where
The cochlear to nuclei to the superior olivary/trapezoid nuclei located in the MO
Information from the superior olivary/trapezoid nuclei in the MO then is carried where
In the lateral lemniscus to inferior colliculi and medial geniculate body
After going through the lateral lemniscus and medial geniculate bodies information from cochlear nerve goes to where
The temporal lobe to reach brodmann areas 41 and 42
What is the vestibular nerve made up of axons from
The vestibular ganglion
Axons of the vestibular nerve carried to where
The vestibular nuclear complex of the medulla oblongata
After traveling to the vestibular nuclear complex of MO info is processed where of the vestibular nerve
In the cerebellum
What bones are located in the tympanic cavity
Malleus, incus, stapes
What bone in the tympanic cavity is the largest and what does it contact with
Malleus and contacts with the tympanic membrane
What does the incus transmit vibration from and to
From the malleus to the stapes
What tympanic cavity bone has its base against the oval window
The stapes
