hi let's talk about the intrinsic laryngeal membranes in this video we'll discuss the
intrinsic laryngeal membranes specifically the quadrangular membranes and conus elasticus
detailing their constituent parts and explaining their functional clinical significances
so the quadrangular membranes are a pair of membranes left and right that sit at the superior
aspect of the larynx they have two constituent parts there are the ary-epiglottic ligaments
the airy epiglottic ligaments are named for their attachments
so they run from the arytenoid cartilage to the epiglottic cartilage and there is one on each side
when invested with mucosa these are the ary-epiglottic folds which we can see
illustrated there making up the lateral aspect of the laryngeal inlet the inferior most or free edge
of the quadrangular membranes are the vestibular ligaments the vestibular ligaments run from the
arytenoid cartilage out to the thyroid cartilage like so so if we can imagine all of this space
would be a quadrangular membrane and on the other side we would have another quadrangular
membrane now that vestibular ligament when invested by mucosa becomes the vestibular fold
or the false vocal fold it has a protective function over the larynx and it can produce sound
so if you think of throat singing or that sound of oh that is vibration of the vestibular ligaments
but it is not phonation also the space between the vestibular ligaments is known as the arima
vestibule the function in totality of the quadrangular membranes is to direct air
in through the laryngeal vestibule so this is an inward movement of air we can contrast that
with the conus elasticus which is a single membrane with several constituent parts it's
oftentimes referred to as the cricothyroid membrane but it is so much more than that
so the three parts are the lateral cricothyroid ligaments which are located there the median
cricothyroid ligament which is located there there's the other lateral cricothyroid ligament
and then it's superior most part the vocal ligament which as you may recall runs from
the vocal process of the arytenoid cartilage to the thyroid cartilage when invested by mucosa the
vocal ligament is the vocal fold aka the vocal cord now the conus elasticus directs air out
through the larynx specifically toward the space between the vocal folds called the rhimoglotidus
now it's that rhimoglotidis that is going to expand as the vocal folds
abduct or narrow as they add duct now for breathing purposes for ventilation the fold
should be maximally abducted or open for phonation those folds need to be not tight
against one another but in relative close proximity so that those folds can vibrate for
phonation now let's take a look at this space in a little larger sense so there's our ary-epiglottic
ligament and fold there's our vestibular ligament in fold so there's a quadrangular membrane
on one side here is the lateral cricothyroid and the medial cricothyroid and then the vocal
ligament the space between these two is known as the laryngeal ventricle
and then the spaces above the laryngeal ventricle are the rima vestibule
and below the rhema glottidis and then below that would be the infraglottic cavity
so we can see these relative relationships between quadrangular membranes and the conus elasticus one
last thing to discuss is the median cricothyroid ligaments important for a cricothyrotomy
cricothyrotomy is the incision of that median cricothyroid ligament and it's done under
emergent situations if one needs airway access there are very good anatomical landmarks that
are palpable so you can feel for the laryngeal prominence if you run your finger inferior from
that laryngeal prominence you'll encounter a divot that's the median cricothyroid ligament
and then just below that is another solid structure and one incises the skin and then
perforates that median cricothyroid ligament and we have an airway what's nice about this
is that there are no major vascular issues lying superficial to this and they're good palpatable er
landmarks now this is only for emergency uses only it's not meant for long-term airway management
so we've discussed the various intrinsic membranes of the laryngoskeleton in their constituent parts
how they hold together various elements of the laryngoskeleton and how they regulate the
movement of air this is your summary slide and i thank you for your time