hi let's talk about the intrinsic laryngeal muscles in this video we'll discuss the intrinsic
laryngeal muscles their functions and innovations will also describe the arteries and nerves which
serve the larynx so sound is shaped not just by the vibration of the vocal folds but also
by the the entirety of the respiratory tract distal to those vocal folds so the extrinsic
laryngeal muscles can lengthen or shorten the the laryngopharynx in the oropharynx and effect
sound the nasal cavity the oral cavity the tongue the lips all of these things can can
affect sound and the quality of one's voice now to to differentiate between extrinsic
versus intrinsic laryngeal muscles extrinsic laryngeal muscles attach some element to the
laryngoskeleton whereas intrinsic laryngeal muscles have their attachments entirely within
the laryngoskeleton so they'll connect one element of the laryngoskeleton in with another element of
the laryngoskeleton and these muscles can affect what's going on in a number of ways so they may
either work directly on the vocal folds either by abducting the folds or abducting the folds
phonation is an endeavor of having more adducted folds so when we speak the folds are brought into
very close proximity whereas ventilation is an ever of abducted folds we were swinging those
folds away to to move as much air through that as possible we can also put more or less tension
on those vocal folds and by increasing tension on the folds we increase pitch by decreasing tension
on the folds we decrease pitch so let's take a look at what these muscles are doing so we have
a handful of muscles to discuss and our first run through these muscles we'll look at them
all superiorly so that we can see what they're doing to the cords so the first muscles are the
current authority muscles that would be these muscles in particular cricothyroid muscles work
on the cricothyroid joint and so they're going to pitch the thyroid cartilage us anteriorly and
then inferiorly and that is going to stretch the vocal ligaments and by stretching or increasing
the longitudinal tension on the vocal ligaments cricothyroid muscles increase pitch there are
also thyroarytenoid muscles thyroarytenoid muscles run between the arytenoid cartilages
and the thyroid cartilage when these contract they actually pulled the aryentoid cartilages forward
thereby decreasing longitudinal tension there we go they are pitch decreases when they move
them forward they also slightly abduct them so we have a slight narrowing of the Rema glottis now
there are specialized parts of the thyroarytenoid muscles one particular set of specialised fibers
insert directly on the vocal ligaments themselves so they're coming across like so we sometimes call
these the vocalist muscles the vocalist muscles are interesting because they're going to increase
lateral tension on the vocal ligaments so if this were a vocal ligament in cross-section by pulling
on that ligament it can flatten out the vocal ligament and that is going to adjust Tambor or
the tonal quality of sound when that vocal fold vibrates and the vocalist muscles can also finally
adjust pitch so whereas most of the thyroarytenoid muscles decrease pitch some fibers can finally
increase pitch which is kind of wild the next set of muscles are very important to us all
near and dear to my heart these are the posterior cricoarytenoid muscles let's pay attention to the
name there so posterior cricoarytenoid cartilage and then they attach to the muscular process of
the arytenoid cartilage and so when these pull that swings the muscular processes post eerily
that swings the vocal processes laterally and that is going to a be duct the vocal fold or open
the rima glottidis this can also put a little bit extra tension on the vocal ligament so it
can increase pitch just a little bit so these are the only muscles that really maintain the
patency of the airway in the larynx so we should be grateful for these muscles we also have the
lateral cricoarytenoid muscles they originate on the lateral aspect of the cricoid cartilage
and also go back to that muscular process like the posterior cricoarytenoid muscles
do when these pull and these tug they swing the muscular processes anteriorly like so and that
is going to swing the vocal process medially so that is going to ADduct the vocal ligaments are
closed the rima glottidis posteriorly - we have the arete muscles that are - we'll see how we
differentiate them these are the transverse and oblique the rete nine muscles they run between
the two arytenoid cartilages and they pull the the to a retinoid cartilages together when
they tug and that is going to also pull the vocal ligaments together so that addicts them or closes
the rhyme o'clock to this so let's take a look at each of these in a little greater detail so let's
start with the posterior cricoarytenoid muscle so here's the cricoid cartilage there we can see the
posterior cricoarytenoid muscles originating from the posterior cricoarytenoid cartilage
laterally there so these muscles are innervated by the recurrent laryngeal nerves the recurrent
laryngeal nerves are branches of the vagus nerve that ascend in the trachea esophageal groove to
innervate most of the intrinsic laryngeal muscles as well as the mucosa inferior from the vocal
folds these posterior cricoarytenoid muscles even though they predominantly are going to a be duct
to the vocal folds they do add a little bit of longitudinal tension to the folds as well so
they can finally increase pitch as as we go but predominantly these are muscles of ventilation
superior to the posterior cricoarytenoid muscles are the areata noid muscles so there are the
transverse or avoid these run transversely and then the oblique areata noid oblique arytenoid
run obliquely and there is even an airy up a colonic part of that that can help act as a
sphincter but generally these muscles when they are stimulated by the recurrent laryngeal nerve
are going to tug the arytenoid cartilages together they glide in that fashion and that is going to
adduct to the vocal ligaments and bring them into place for foundation so basically both transverse
and oblique a retinoid muscle do the same thing here oblique arytenoid muscles also have some
function in helping to close the laryngeal Inlet as well this is a little bit of an odd view in
the cat I've Eric view here what we have is the thyroid lamina there has been reflected away and
we can see the cricoid cartilage there here's the posterior cricoarytenoid muscle coming up to
the muscular process and then here's the lateral cricoarytenoid muscle coming over to that lateral
process and when these pull like so we could probably see it better here that is going to
pivot the Arita cartilages around so the muscular process goes anteriorly and the vocal process goes
immediately lateral cricoarytenoid muscles are also innervated by the recurrent laryngeal nerve
so when stimulated these are going to add duct the vocal folds and close the rhyme eclectus so
to bring them into close approximation either for phonation or even for the valsalva maneuver that
foul salva maneuver is when one maximally closes the Rima glottidis and then puts pressure so that
at straining sound like when you're lifting a desk or defecating that's that's the valsalva
maneuver or a modified valsalva maneuver then we have the thyroarytenoid muscles so they're running
between the arete node cartilages and the thyroid cartilage they pull the Irate annoyed cartilages
anteriorly that decreases longitudinal tension or lowers the pitch we also have vocalist fibers
as we discussed that can change the shape of the vocal ligament when they tug on it more flat to
change timbre and this can also finally adjust pitch as well and like everything else that
we've to guest so far these are innervated by the recurrent laryngeal nerves no surprise there now
to the the rebel the oddball the the hero here the cricothyroid muscle so running between the cricoid
cartilage and the thyroid cartilage you can see two bellies to it there is the cricothyroid
muscle that works upon the cricothyroid joint and when this pulls it pulls the thyroid cartilage
anteriorly and inferiorly so vectorially like that and that really puts a lot of tension on
those vocal ligaments so that's going to lengthen and tense the vocal cords and that is going to
be a massive increase or of pitch power increase or a pitch these are the oddball muscles because
they are the only intrinsic laryngeal muscles not innervated by the recurrent laryngeal nerve this
is an error these are innervated by the external branch of the superior laryngeal nerve so the
superior laryngeal nerve has external and internal branches its external branch is muscular so it's
efferent to the external print to the cricothyroid muscle as well as the cricopharyngeal part of the
inferior for regional constrictor muscle now let's take a look at neurovascular tree let's start with
the nerves so the entirety of the larynx is innervated by branches of the vagus superior
lee we have the superior laryngeal nerve which is a branch of the vagus descending down in the neck
and then this ramifies into an internal branch that goes through a hiatus of the thyrohyoid
membrane along with the superior laryngeal artery and this internal branch is going to carry fibers
that are a ferrant from the mucosa of the larynx superior to the vocal folds so if we can imagine
that the vocal folds there all of the eighth parents are going there those are also carrying
secreto motor fibers to the mucosa so that all of the glands in the mucosa can therefore secrete
as necessary complements of Vegas the external branch of the superior laryngeal nerve descends
down it does not go in and it goes directly to the cricothyroid muscle there will also be a
branch of it that goes out to the cricopharyngeal part that would be that part of the inferior for
Injil constrictor so little dual innervation there the recurrent laryngeal nerve recurrent laryngeal
nerves also branch from the vagus on the right side they wrap around the subclavian artery on
the left side they wrap around the concavity of aorta and then they ascend in this trachea
of esophageal groove trachea esophagus trachea esophageal groove along with the inferior thyroid
artery and these are coming up and they're going to innervate all of the other intrinsic laryngeal
muscles with the exception of the cricothyroid muscle these are also efferent they conduct a
ferrant fibers from the mucosa below the vocal folds and they are secrete a motor to that same
mucosa this recurrent laryngeal muscle is also in part going to innervate that cricopharyngeal part
of the inferior Franjo constrictor so this part of the inferior original constrictor cricopharyngeal
part has three sources of innovation one the pharyngeal plexus to the external branch of the
superior laryngeal nerve and three the recurrent laryngeal nerve so that's a lot of innervation for
a little bit of muscular real-estate now let's take a look at some of the arteries which serve
the larynx so the Larynx is served by the superior laryngeal artery superior laryngeal artery is a
branch of the superior thyroid artery which is a branch of the external carotid artery the inferior
laryngeal artery which accompanies the recurrent laryngeal artery is a branch of the inferior
thyroid artery which is a branch of the thyroid cervical trunk which comes off the first part of
the subclavian artery so the two branches which serve the thyroid superior and inferior thyroid
artery give rise to the superior in inferior laryngeal arteries respectively and that leads
us to our assessment question for the video and that is a person wanting to powerfully elevate
the pitch of their voice must use which nerves to do so the external branches of the superior
laryngeal nerves that's sounding pretty good the internal branches of the superior laryngeal nerve
nope that's largely sensory one of the mnemonics that I use to think of this is you know a muscular
externally and I am sensitive internally to describe these branches recurrent laryngeal nerves
that's in in the mix - and then vagus nerves Vegas probably much much much too - general here let's
think powerfully elevate pitch well there are a number of muscles which do elevate pitch but
the one that is the power elevator of pitch is the cricothyroid muscle and that is the oddball muscle
because is the only one not innervated by the recurrent laryngeal nerve its innervated by the
external branches of the superior laryngeal nerves thank you very much for your time