ear and larynx Flashcards
week 14
what are the three basic functions of the larynx
- protect airway
- generate intra-thoracic pressure
- sound production (phonation)
between the vocal fold and the vestibular fold is a pocket called?
ventricle
cricothyroid joint
- rotes about what axis?
- slides in what direction?
- adjusts tension of the?
- rotates about horizontal (mediolateral) axis
- ant-post sliding
- adjusts tension on the vocal folds
what is the movement of the cricoarytenoid joint?
what direction does it slide? rotate?
abduction and adduction of vocal fold
- sliding/rocking ant-post, and med-lat
- rotatea bout vertical axis
what is the main nerve of the larynx
vagus nerve (CN X)
broken down into branches:
- superior laryngeal nerve: internal branch, external branch
- recurrent/inferior larygneal nerve
What are the unpaired cartilages of the larynx?
thyroid, cricoid, epiglottis
What is the paired cartilage of the larynx?
arytenoid
what are the two processes of the arytenoid cartilages?
What are they each an anchor for?
a vocal process and a musclar process
- vocal process is an anchor for the vocal ligament (“cord”)
- the muscular porcess is an anchor for muscles that move the arytenoid
What structure protects the vocal folds from aspireated food and drink?
vestibular fold (false vocal fold)
What are the adductors of the vocal fold? what are their origins and insertions?
- oblique and transverse arytenoid msucles
- origin: one arytenoid insertion: other arytenoid
- the oblique muscel has a few fibers that continue into aryepiglottic fold
- lateral cricoarytenoid
What is the role of the adductor muscle ofthe vocal fold: lateral cricoarytenoid ?
pulls on the muscualr process from antieroly, rotating the arytenoids around a vertical axis = thereby adducting the vocal ligaments
What is the abductor of the vocal ligaments (folds)?
what is the origin? insertion?
posterio cricarytenoid muscle
origin: lamina of cricoid
insertion: muscular process of arytenoid
What is the action of the posterior cricoarytenoid?
pulls the muscular processes toward the midline and spread aprat the vocal ligaments
- point of vulnerability in humans, if paralyzed will be very challenging for us to live
What are the adjustors of the vocal ligaments (folds)?
- Cricoarytenoid
- thyroartenoid
- vocalis
what is the role of the thryoarytenoid msucle?
slackens the vocal ligament
What is the role of the vocalis muscle?
tighten specific segments of the vocal ligaments for very precise ptich control
What is the
origin: posterior surface of thyroid cartilage
insertion: musuclar processs of arytenoid cartilage
action: shortens and relaxes vocal ligaments - lowering pitch by reducing tension
of thyroartenoid muscle?
origin: posterior surface of thyroid cartilage
insertion: musuclar processs of arytenoid cartilage
action: shortens and relaxes vocal ligaments - lowering pitch by reducing tension
Vocalis (superomedial part of thyroarytenoid)
origin:
insertion:
action:
origin: thyroid cartilage in midline
insertion: vocal ligament near vocal process of arytenoid cartilage
action: local adjustment of vocal ligament, changes shape of folds (thickness and tension)
What are the extrinsic muscles of the larynx? and their roles?
- suprahyoid: generally raise the larynx
- infrahyoid: generally lower the larynx
used in swallowing and to stabilize the hyoid so the tongue can move in speech
the internal branch of the superior laryngeal nerve is purely ?
sensory
the external branch of the superior larygneal nerve is motor innervation to what muscles?
- cricothyroid muscle
- inferior pharyngeal constrictor
after the recurrent larygneal nerve passes behind the cricothyroid joint it gets the new name of?
inferior laryngeal nerve
what is the blood supply to the larynx?
external carotid artery:
- superior thyroid artery
- superior laryngeal artery
subclavian artery
- thyrocervical trunk
- inferior thyroid artery
- inferior larygneal artery
The external ear is made of the auricle or pinna - what is the role?
funnel and localize sound
What is the role of the external auditory canal channels?
sounds to the tympanic memebrane or eardrum.
also protects the middle ear and acts as a resonator
What are the functions of the middle ear?
3 things
- transfers sound waves from air to the liquid of the inner ear
- acts as a transformer, increasing the strength of the signal (ipedacne matching)
- protects the inner ear from excessivley loud sounds
What are the ossicles of the ear?
malleus, incus, stapes
What kind of joint are the ossicles of the ear?
consist of a chain with two synovial joints
- a joint between the malleus and incus
- a joint between the incus and stapes
What ossicle of the ear is in contact with the tympanic membrane (ear drum)?
malleus
what ossicle of the ear rests on the oval window (membrane between the middle ear cavity and the fluid filled inner ear)?
footplate of the stapes
describe sound waves traveling through the ear, with respect to the ossicles?
- sound waves traveling in air beat on the tympanic memebrane (ear drum)
- causes malleus to move inward w/ high pressure zone
- malleus and incus rock as one around an axis running through two ligaments
- this rotation causes the long limb of the incus to pus hthe stapes into the oveal window, setting up a fluid wave in the inner ear
- problem occurs when waves traveling through air are transferred to a fluid –> lost of force (impedance0
What are the two mechanism in the middle ear to match impedance at the air/fluid interface
- surface area of the oval window is much smaller than that of the tympanic membrane (1:21) pressure =force//surface area
- the handle of the malleus is longer than the long limb of the incus (1.3:1.0) thus the force is multiplied by this leverage ratio.
overall the force of sound is increased by a factor of 2.73 or 29 decibles which is almost the air/fluid impedance at 30 decibels = aka we are pretty much hearing things as they actually sound.
What are the two tiny muscles in the midle ear cavity that work to decrease sound transmission when sounds are too loud?
tensor tympani - which lies above the eustachian tube and sends a tendon to the manubrium ofthe malleus
What occurs when the tensor tympani fires?
pulls on the malleus which tenses the tympanic membrane (ear drum) making it more resistant to incoming sounds.
hand on drum to tense the drum and stop the sound
what is the tensor tympani innervated by?
trigeminal nerve
What is the smallest muscle in the body? What does it do when it contracts?
stapedius (back wall of middle ear cavity)
- when it contracts, pulls the stapes awa yfrom the oval window, reducing sound transmission to the inner ear
What is the stapedius muscle innervated by?
facial nerve
What occurs when the tensor tympani and stapedius contract?
restrict movement of the ossicles, thus protecting inner ear
What forms most of the lateral wall of the middle ear?
tympanic membrane (ear drum)
What nerves are in or near the middle ear?
facial nerve (branch -chorda tympani), tympanic plexus (glossopharyngeal)
Waht two structure on the miedial wall of the middle ear cavity are assocaited with the inner ear?
oval window and round window
- both are covered by a membrane and communicate iwth spaces in the inner ear
What does the membranous labyrinth of the inner ear consist of?
cochlea (anterior), vestibule (mid), semicircular canals (posterior)
Cochlea: the cochlear duct divides the bony passage within the cochlea into two paths, what are they?
- the vestibular duct
- the tympanic duct
What is found in the cochlear duct?
What is found in the vestibular duct?
What is found in the tymapnic duct?
- endolymph
- perilymph
- perilymph
do the vestibulear duct and tympanic duct of the inner ear ever connect?
yes
the vestibular duct is connected to the tympanic duct at the end of the spiral (helicotrema)
What is the pathway of sound wave going up the vestibular duct and tympanic duct?
- the stapes sits against the membrane of the oval window…which leads to the vestibular duct
- when stapes beats against oval window, a fluid wave travels to vestibular duct all the way to the end of the spiral
- the fluid wave then continues to the tympanicduct all the way back to the round window
- the fluid wave passes above and below the cochlear duct- bending the cochlear dut
what is the cochlear duct bounded by?
the cochlear duct is bounded by the vestibular memebrane and the basilar membrane
describe what happens when the hair cells detect sound (they lie within the cochlear duct, sitting on the stiff basilar membrane)
- when the basilar memebrane is deflected by the surrounding waves in the vestibualr and tympanic duct, an action potention is set up in the hair cells and transmit back to the brain in the cochlear branch of the vestibulocochlear nerve (CN VIII)
- the basilar membrane gets less stiff (proximal to distal) therefore a wave of a given force will deflect the membrane intially at one point. the hair cells in the basilar memebrane provide us info about sound waves (pitch)
What produces a pressure wave in the perilymph of the vestibualr duct (scalae vestibuli) and tympani?
rocking of the stapes in the oval window
the further out from the cochlea the higher the pitch
What about the other half of the inner ear – the vestibualr system?
similar to cochlear system
- has a bony labyrinth which is filled with perilymph and a membranous labyrinth filled with endolymph
- instead of one main structure like the cochlea there is 3 semicircualr canals and a central area with two components: the utricle and saccule
What does the utricle and saccule sense from the vestibular system?
linear acceleration
Where does neuroreception (hair cells) occur in the ear for the vestibular system?
- cristae in the semicircular canals
- maculae in the utricle and saccule
talk about the semicirucalr canals and the changes in angular velocity?
- cause the hair cells in the cristae to bend
- The semicircular canals send the brain information about changes in angular acceleration. As you spin around an axis, a gel inside the crista deflects based on centrifugal force. This deflection bends the hair cells differentially, setting up an action potential which is sent down the vestibular branch of CN VIII and interpreted as angular acceleration. The semicircular canals are at 90 degrees to each other and the proportion of stimulus to each canals tells us which way our head is spinning.
the utricle and saccule, changes in linear acceleration causing bending of the hari cells in the macuale –talk about this.
The vestibule sends information about changes in linear acceleration
Utricle: horizontal linear acceleration
Saccule: vertical linear acceleration
Here, the momentum of a linear acceleration causes small stones to roll across a bag of gel that contains the hair cells. Thus, some hair cells suddenly lose the pressure from the stone above while others receive additional pressure. This difference (sent along vestibular branch of CN VIII) is interpreted as linear acceleration, The proportion of stimulus in the utricle versus saccule allows the brain to work out the direction of the linear acceleration.
Saccule = vertical acceleration elevator
Utricle = horizontal acceleration
