Anatomy Flashcards
components of the temporal bone (4)
squamous, mastoid, petrous and tympanic.
name the prominence of the superior semicircular canal on the middle fossa floor
arcuate eminence
Potential paths of tumor spread from EAC (3)
Bony-cartilaginous junction, the foramen of Huschke (to infratemporal region and deep lobe of parotid), and the fissures of Santorini (to superficial lobe of parotid).
Middle ear landmarks of the facial nerve (3)
Cochleariform process, the oval window, and the pyramidal eminence
What is the most vulnerable portion of the ossicular chain
long process of the incus, because has a single nutrient vessel and lacks collateral circulation
Where is the supratubal recess located
At the anterior extreme of the attic and superior to
the opening of the eustachian tube
Importance of supratubal recess
It is the site in which cholesteatoma or blind surgical dissection can injure the facial nerve. The geniculate ganglion is located just deep to its medial wall and may be dehiscent.
Why is the labyrinthine segment of facial so vulnerable to injury (3)
- watershed vertebrobasilar/external carotid circulation,
- narrow bony canal,
- proximity to the genicular ganglion where herpetic infections and traumatic distortion may produce nerve swelling and entrapment
Wha is used as a surface landmark that
estimates the location of the middle fossa floor?
Temporal line, located about 5 mm inferior to the lowest level of the middle fossa floor.
the jugular foramen is formed by
petrous and occipital bones
parts of jugular foramen and who separates them
Pars venosa (ant) and pars nervosa (post). Separated by jugular spine
What marks the superiormost limit of the jugular foramen?
The cochlear aqueduct, medial to jugular spine and opens into the scala tympani at the cochlear base
What CN enters adjacent to the opening of the cochlear aqueduct?
Glossopharyngeal nerve IX
where does the Jacobson’s nerve come from?
Parasympathetic fibers from the glossopharyngeal nerve
What separates the carotid from the jugular bulb?
the Keel
a landmark for the main trunk of the facial nerve as it exits the temporal bone
tympanomastoid suture line
Blood supply of the external ear
posterior auricular and superficial temporal vessels fro external carotid
Hillocks of His derivates from 1rt branchial arch
tragus and helix. Auriculotemporal branch of the trigeminal nerve
hillocks of His derivates from 2nd branchial arch
antihelix, antitragus, lobule, and
inferior helix. Cutaneous branch of the facial nerve
Layers of the tympanic membrane (4)
skin (ectoderm)
outer radidated fibrous layer (manubrium inserts)
deeper circular fibrous layer (mesoderm)
Middle ear mucosa (endoderm)
where is the sinus tympani
a recess that lies posterior to the oval and round windows, and medial to the vertical facial nerve.
Importance of sinus tympani
may have occult cholesteatoma
structure attached to the pyramid eminence, where is located
Stapedial tendon and just anterior to the second genu of the facial nerve
divisions of the epitympanum (3)
(1) Prussak’s space, medial to pars flaccida and
lateral to the head and neck of the malleus;
(2)anterior compartment to the malleus;
(3) the posterior compartment, which communicates with the antrum
VII CN General visceral efferent fibers (3)
- nervus intermedius: lacrimal gland
- greater superficial petrosal nerve and
pterygopalatine ganglion: seromucious glands in nose - chorda tympani and the submandibular ganglion: Submandibular and sublingual glands
VII CN special sensory fibers
Chorda tympani–taste: anterior two thirds of the tongue greater superficial petrosal nerve–tonsillar
fossae and palate
VII CN somatic sensory fibers
sensation to touch of the EAC and conchal skin of the auricle
VII CN special visceral efferent fibers
facial expression, the stapedius muscle, stylohoid
muscle, and posterior belly of the digastric
How is the cochlea organized?
Tonotopically, low freq in apex and high in base
Describe afferent auditory neurons
Bipolar, body in spiral ganglion and connect the hair cells to the central auditory system.
Name of bone that allows the auditory nerve fibers from the IAC to the hair cell synapse
Modiolus -core of the cochlea-
what does divide the spiral lamina?
partial division of upper and lower cochlear chambers:
Scala vestibuli (upper) and scala tympani (lower)Which scala does the round window go?
marking entrance to scala tympani of cochlea; vibrates with opposite phase to vibrations entering inner ear through oval window; allows fluid in cochlea to move ensuring that hair cells of basilar membrane will be stimulated for audition.
stapedius muscle
1:2 tympanic muscles of ear; attached to the stapes & pulls stapes posteriorly to tighten ossicular chain with contraction of tensor tympani muscle to reduce range of movement of tympanic membrane & transmission of lower frequency sounds
tensor tympani muscle
2:2 tympanic muscles of ear; extends from anterior wall of middle ear space; inserts into upper manubrium of malleus; contracts to pull malleus anteromedially; contracts with stapedius muscle to reduce range of movement of tympanic membrane & transmission of lower frequency sounds
utricle
w/in vestibular system 2:2 larger compartments (1:2 saccule; 2:2 utricle); filled with small stones, otolyths, & fluid used to stimulate hair cells inside compartments; responsible for detecting acceleration of the head in a particular direction by detecting displacement of fluid
saccule
w/in vestibular system 1:2 larger compartments (1:2 saccule; 2:2 utricle); filled with small stones otolyths & fluid used to stimulate hair cells inside compartments; responsible for detecting acceleration of the head in a particular direction by detecting displacement of fluid
scala vestibuli
1:3 inner chambers of cochlea spiral; filled with perilymph; separated from scala media by Reissner’s membrane; extends from vestibule of the ear to helicotrema where it joins scala tympani
scala tympani
3:3 inner chambers of cochlea spiral; filled with perilymph; separated from scala media by basilar membrane; ends at round window & basil end; meets with scala vestibuli at the helicotrema at apex of cochlea
osseous spiral lamina
thin bony shelf that winds around modiolus like thread of a screw; projects halfway across cochlear canal; creates division of scala vestibuli & scala tympani; forms point of attachment for scala media
scala media
membranous labyrinth of cochlea; resides between scala vestibule & scala tympani; houses organ of corti: center organ of hearing & tectorial membrane; filled with endolymph; also called cochlear duct
cochlear duct contents
Reissner’s membrane, basilar membrane, organ of Corti, outer hair cells, inner hair cells, spiral limbus, tectorial membrane, stereocilia, traveling wave
organ of Corti
organ of hearing; resides on basilar membrane within scala media; contains 1 row of inner hair cells & 3 rows of outer hair cells
outer hair cells
3 rows of hair cells w/in organ of Corti; stereocilia on top of hair cells are embedded into the tectorial membrane; send Fz to CN VIII when bent from sound wave
inner hair cells
1 row separated from outer hair cells by tunnel of Corti; multiple nerves are attached to each hair cell; not embedded in tectorial membrane
tectorial membrane
overlays stereocilia of organ of Corti; originates at spiral limbus; stimulated by wave of endolymph fluid within scala media & moves stereocilia of outer hair cells embedded in it & creates enough movement to stimulate inner hair cells
traveling wave
wave action of basilar membrane; when basilar membrane moves, it creates a travelling wave along and within basilar membrane; wave is strongest where perilymph wave of the scala vestibuli reached its peak
Vestibulocochlear nerve
CN VIII auditory nerve; extends from brainstem into cochlea; tons and tons of nerve fibers extend from CN VIII to innervate inner and outer hair cells; 10 CN VIII nerve fibers to 1 inner hair cell & 10 outer hair cells to 1 CN VIII nerve fibers; Afferent (sensory) and efferent (motor); stereocilia bend away from modiolus, release of glutamate; accumulation of glutamate leads to neural firing
selective enhancement
strengthening of some Hz’s of incoming signal and weakening or dampening other Hz; select energy at resonant frequency of chamber: reject energy at other frequencies & boosts strength of signal through resonance at resonant frequency; pinna & external auditory meatus amplify frequencies between 1,500Hz and 8,000Hz same as speech Hz; amplifies ~ 20dB; passive enhancement
resonant frequency
frequency of stimulation to which a resonant system responds most vigorously, depending on the shape of system
impedance matching
middle ear mechanism increasing pressure of signal arriving to cochlea to counter act loss of spl when energy converts from air to physical to fluid based
shearing action
outer hair cells’ stereocilia embedded in tectorial membrane are bent
superior olivary complex
SOC; 2nd step of afferent process for 2:3 pathways from CN (1 bipasses SOC to IC); locates sound origin: 1) measures time difference in sound arrival btwn ears; 2) measures amplitude difference btwn ears
IC; 2nd & 3rd step of afferent information; crossover to opposite sides of CNS; re-integration of information;
Inferior colliculus
medial geniculate body
MGB; 4th step of afferent acoustic information; located in thalamus; projects information to primary auditory cortex in temporal lobe
cerebral cortex
final afferent destination of acoustic information; within in temporal lobe; houses Heschl’s gyrus: primary reception of acoustic information; also tonotopic mapping;
3 functions of outer ear
1) collect sound; 2) boost frequencies 1,500 - 8,000Hz; 3) boost intensity of these frequencies ~20dB
impedance
resistance to the flow of energy; 3 methods to counter impedance: 1) Large TM to small Oval Window: +25dB; 2) Lever difference; malleus to stapes:+2dB; 3) Buckling TM, comparatively less malleus movement: +4 to 6dB = ~31dB increase
innervation of hair cells
Afferent (sensory) innervation: 1 inner hair cell is innervated by up to 10 VIII nerve fibers; 1 outer hair cell shares innervation by 1 VIII nerve fiber with 10 other outer hair cells; from cochlea up
Efferent (motor) innervation: Inhibitory effect to reduce afferent activity caused by hair cell stimulation; from brain down
Neural Pathways
1) Cochlea Nucleus (CN) 1st step of processing sound; in dorso-lateral (lower) brainstem; 2) SOC 2nd step for 2:3 pathways from CN: binaural interaction & locates sound origin; 3) IC 2nd step for 1:3 pathways from CN & 3rd step for 2:3 that stopped at SOC; all acoustic info is integrated back together; also where they crossover (decussate) to opposite sides of CNS; IC higher up on brainstem; 4) MGB; 4th step of afferent acoustic information; located in thalamus; projects information to primary auditory cortex in temporal lobe 5) final step to Heschl’s gyrus & cerebral cortex
