hi let's talk about the neurovasculature of the larynx and the pharynx
and let's begin with the pharyngeal plexus which is a nervous plexus serving the pharynx and the
muscles of the soft palate the pharyngeal plexus gets input from three sources there are somatic
sensory fibers granted from the glossopharyngeal nerve cranial nerve 10 which we can see here
sharing its posterior association with the stylopharyngeus muscle
they also the plexus also receives somatic motor fibers from the vagus nerve which we can see
here just one of the constituents of the carotid sheath along with the internal jugular vein and
the common carotid artery the vagus nerve also shares visceral motor fibers or parasympathetic
fibers to this plexus as well and then finally there are fibers from the superior cervical
ganglion of the cervical sympathetic trunk that trunk isn't visible on the right here
but on the left we can see that superior cervical ganglion there and there's the remainder of the
trunk we'll also get a better view of the trunk in a subsequent slide it's probably important
to realize that that cervical sympathetic trunk enjoys a posterior medial relationship to the
carotid sheath so it's not within the sheath but it's found just posterior and medial and a little
outside of that sheath so that's a great place to uh to find that cervical sympathetic trunk
the carotid sheath contents are probably very well viewed here the carotid sheath itself is
a condensation of deep cervical fascia that's going to surround the common carotid artery
the vagus nerve cranial nerve 10 as well as the internal jugular vein as well as branches of the
the vagus nerve as it is ascends higher within the the neck we also have the branches of the common
carotid artery so the internal carotid artery and the external carotid artery and the proximal
portions of those external carotid artery branches sometimes we also will have the proximal parts of
cranial nerve 9 glossopharyngeal as well as cranial nerve 11 the accessory nerve because
cranial nerves 9 10 and 11 all leave through the jugular foramina with the internal jugular vein
so the vagus nerve is going to be an important recurring theme throughout our discussions of
anatomy in this course and we can see it here it takes more of a posterior intermediate
position within the carotid sheath um and it's going to be a dominant parasympathetic
player for elements of the neck thorax as well as the abdomen as we'll see in subsequent videos
the cervical sympathetic trunk is a continuation of the sympathetic trunk which runs the length
of the bony spine so from the inferior part of the basic cranium of the skull
down to the coccyx which is the distal most portion of the the bony spine within the pelvis
we have these sympathetic trunks on either side and these trunks consist of ganglia connected
by fibers the ganglia of the neck are condensed so there's a superior cervical ganglion which is
one of the larger cervical ganglia and it consists of fused ganglia from the first
cervical nerve through the fourth cervical nerve there's also a middle
cervical ganglion which is variably present we can see that right here the middle cervical
ganglion consists of fused ganglia of c5 and c6 and then there's an inferior cervical ganglion
which sometimes is going to fuse with the ganglion the first thoracic ganglia but it's at least the
fused c7 through c8 and oftentimes it includes t1 if that's the case we refer to it as the cervical
thoracic ganglion also known as the stellate ganglion we can also see lateral within
this image the internal jugular vein which is the main vein that drains the brain of blood and also
receives tributaries from the the face as well and the common carotid artery
so now let's take a look at some of the branches of the vagus nerve here we're looking at an
anterior lateral view of the neck uh there's the thyroid cartilage there there's the thyroid gland
there here's the common carotid artery and there's the internal jugular vein they've been separated
so as to reveal the vagus nerve which would be deep within the uh the carotid sheath
and um it's it's difficult to to visualize this but coming down we can see this branch here just
highlighting it and that branch these are descending down through
the carotid sheath and if we follow these branches we can see that this branch is the
internal branch of the superior laryngeal nerve and this branch
is the external branch of the superior laryngeal nerve superior laryngeal nerves you can barely see
right there the internal branch of the superior laryngeal nerve is going to be entirely somatic
sensory as well as visceral motor to the mucosa superior to the vocal folds so it will conduct
all afferent back from superior to the vocal folds and it will also be secreto motor to
that mucosa as well the external branch of the superior laryngeal nerve is muscular
it's somatic motor to the cricothyroid muscle
we can also see here recurrent branches of the superior laryngeal nerve as well as
a or i should say an internal branch there we see
there that's the internal branch of the superior laryngeal nerve here are the recurrent branches
this is the right recurrent laryngeal nerve and here is the left recurrent laryngeal nerve
these recurrent laryngeal nerves are going to take different courses at the root of the neck
so on the right side it wraps around the subclavian artery on the left side
it wraps around the arch of the aorta so the left recurrent laryngeal nerve is lower down
in origin than the right then both of them move towards the tracheal esophageal groove
of which they've been dissected out of to ascend up to the larynx some sources will call them
the inferior laryngeal nerves when they pass the cricoid cartilage there but there's no need to do
that we can continue to call them the recurrent laryngeal nerves these are going to serve all
of the intrinsic muscles of the larynx with the exception of cricothyroid muscle which is served
by the external branch of superior laryngeal nerve and these will also serve the mucosa inferior to
the vocal folds so they will be somatic sensory and they will be secreto motor to that mucosa
now we can see the common carotid artery and its terminal branches the internal carotid
artery and the external carotid artery that internal carotid artery is going to ascend
the remainder of the neck without any branches to the neck and it's going to enter the skull through
the carotid canal of the temporal bone where it's going to be one of the dominant blood supplies
to the cerebral arterial circle also known as the circle of willis a branch of it will
exit the skull as the ophthalmic artery to serve the orbit and the superior brow
the proximal portion of this artery is dilated and we refer to that as the carotid sinus and in the
walls of the carotid sinus there are special baroreceptors or stretch receptors which can
send important autonomic information up to the brain to relate the blood pressure to the brain
so it's a surrogate for if there's adequate blood flow the external carotid artery is going to have
many branches that supply the neck and the face the first anterior branch here is the superior
thyroid artery which we can see continuing on down to serve the thyroid gland there the other
branch off of that or i should say the only branch off of that is the superior laryngeal artery to
supply the larynx with blood now the the thyroid and the larynx are also supplied by branches
of the thyrocervical trunk if you recall the thyrocervical trunk is of the first part of the
subclavian artery there's the thyrocervical trunk and we have an inferior thyroid artery
which serves the thyroid gland and parathyroid glands and from that but not visible here there
is an inferior laryngeal artery but if we come over here we can see the inferior thyroid artery
and the inferior laryngeal artery coming off of that so when we think about the blood supply to
the larynx there are two laryngeal arteries a superior and an inferior the superior is
a branch of the superior thyroid artery which is a branch of external carotid
the inferior is a branch of the inferior thyroid artery which is a branch of the
thyrocervical trunk thank you very much for your time