hi let's talk about the intrinsic laryngeal muscles in this video we'll discuss the major
intrinsic laryngeal muscles and explain how their actions affect the vocal folds and or phonation
and by that i mean how they adjust pitch and timbre so the intrinsic laryngeal muscles connect
elements of the laryngoskeleton to other elements of the laryngoskeleton we can contrast them with
extrinsic laryngeal muscles which connect outside structures to the larynx for instance
the longitudinal muscles that we discussed in the context of the pharynx are examples of extrinsic
laryngeal muscles intrinsic laryngeal muscles are going to affect one of two things either
the position of the vocal ligaments and by the ligaments i also mean the folds or the tension on
the vocal ligaments and folds in terms of position the muscles may either abduct that's abduct or
a deduct or adduct abducted folds lead to a larger rima glottidis whereas adducted folds
lead to a narrower rima glottidis in terms of tension it's probably best to just understand
that tension is proportional to pitch or frequency so the greater the tension the higher the pitch
the lower the tension the lower the pitch so let's take a look at
some of these muscles and let's start with my favorite the posterior cricoarytenoid muscles
the names of these muscles reflect their attachment so posterior crico-arytenoid muscles
originate on the posterior aspect of the cricoid cartilage and insert on the muscular process of
the urinoid when they contract they pivot the muscular process of the arytenoid cartilage
laterally so they are abductors of the vocal folds they open the rhema glottidis and this is
maximally opened for ventilation these are the only muscles which do this in addition they
slightly pull the arytenoid muscles posteriorly and this is going to ever so slightly increase
vocal ligament tension and pitch these are innervated by the recurrent laryngeal nerves
the transverse and oblique retinoid muscles are named as a group because they sit atop one another
the transverse muscles fibers run transversely as such the oblique muscle fibers run obliquely
and they really attach a retinoid cartilage to a retinoid cartilage
the transverse arytenoid muscles they are going to adduct the retinoid cartilages and as such also
the vocal ligaments so they're closing the rhema glottidis which is the position for phonation the
oblique arytenoid muscles also do this but they also have this extra airy epiglottic part and this
is within the airy epiglottic fold which helps to serve as a sphincter for the laryngeal inlet both
of these muscles are innervated by the recurrent laryngeal nerves we also have the lateral cricoid
retinoid muscles so think we had posterior cricoarytenoid muscles from the posterior
aspect of the cricoid to the muscular process of the arytenoid the lateral cricoid retinoid
muscles originate on the lateral aspect of the cricoid and also go to that muscular process
so here we can see the posterior cricoarytenoid muscle going to that muscular process and then
here is the lateral crico-arytenoid muscle so they're on opposite sides of that muscular process
when the lateral critical retinoid muscles contract they are going to medially pivot
the muscle the vocal process thus adducting the vocal ligaments thus closing the rhema glottidis
so this is the position for phonation and then even whispering or even a modified vowel salva
well maneuver that's the the sound that you make when you gird your insides
when you push air against your vocal folds it's very protective for lifting that's
why people grunt when they lift and these are innervated also by the recurrent laryngeal nerves
we also have the thyroarytenoid muscles thyrothyroid retinoid muscles these muscles run
between the thyroid cartilage and the aretenoid cartilages and when they contract they protract
the aritenoid cartilages they move them forward thus decreasing tension on the vocal ligaments
thus lowering pitch there are specialized portions of these muscles so for instance
immediately adjacent to the vocal ligament specialized fibers of the thyroarytenoid muscles
known as the vocalist muscles are going to pull on the vocal ligaments and if you can imagine
this is a cross-section of the vocal ligament when those fibers pull on it it increases
lateral tension and it changes the shape of the vocal ligaments so this can affect timbre or the
tonal quality of sound and it can also increase pitch ever so slightly so it can finally adjust
pitch whereas the main body of thyroid retinoid muscle decreases pitch these vocalist muscles
increase pitch finally there's also a thyroepiglottic part this thyroepiglottic part is
between the thyroid cartilage and the epiglottis as its name suggests it ascends and it is a
dilator of the laryngeal inlet it helps to pull that airy epiglottic fold slightly out of the way
so as to let more air in these are also all innervated by the recurrent laryngeal nerves
and then finally we have the cricothyroid muscle cricothyroid muscle runs between
the thyroid cartilage and the cricoid cartilage and when these contract they tip
the thyroid cartilage forward thus putting tension on the vocal ligaments because this is now further
thus increasing pitch the cricothyroid muscle is unique among all of the intrinsic laryngeal
muscles in that it is not innervated by their current laryngeal nerve it is innervated by the
external branch of the superior laryngeal nerve so we've discussed the various
intrinsic laryngeal muscles and their functions in terms of the rhema glottidis or tension
on the vocal ligaments this is your summary slide and i thank you for your time