hi let's talk about the pharyngeal plexus in this video we'll discuss the contributions and neuro
modalities of the glossopharyngeal nerves the vagus nerves and the cervical sympathetic trunks
to the pharyngeal plexus our story is going to begin at the jugular foramen through which
several very key anatomical features that we'll discuss today are transported out of the skull
the jugular foramen is a window between the occipital bone and the temporal bone through which
the internal jugular vein for which the foramen is named cranial nerve 9 the glossopharyngeal nerve
cranial nerve 10 the vagus nerve and cranial nerve 11 the accessory nerve are all transmitted out of
the neurocranium just anterior to the jugular foramen there is an opening in the temporal
bone called the carotid canal and that's the passageway that the internal carotid artery
enters into the cranial vault now i mentioned this because all of these features taken together
are going to be surrounded by condensations of deep cervical connective tissue or fascia
they comprise something called the carotid sheath and this carotid sheath is going to bundle these
elements together as they are transmitted through the neck so the major constituents within the
carotid sheath include the carotid arteries common internal external and their various branches
the internal jugular vein and cranial nerve 10 throughout and proximally cranial nerves 9 and 11.
so let's take a look at the posterior aspect of the pharynx to see how these nerves come into play
so there is our jugular foramina on either side here we can see the common carotid artery
ascending up and at this point it's probably the internal carotid if it's heading towards the skull
and let's take note of two of those nerves that were being transmitted through the jugular
foramen the glossopharyngeal and the vagus the glossopharyngeal nerve we can see descending down
here and this happens on both sides and it forms a close association with the stylopharyngeus muscle
and then it dives down deep between the two the glossopharyngeal nerves are the somatic sensory
input for the pharyngeal plexus or the afferent fibers the other nerve the vagus nerve descending
down here and it does on both sides it's going to send out a pharyngeal branch that pharyngeal
branch is going to conduct somatic motor fibers or efferent fibers to the pharyngeal plexus so the
glossopharyngeal nerve is the somatic sensory or afferent provider to the plexus the vagus nerves
are the somatic motor or the efferent provider to the plexus in addition to this the vagus nerves
are also transmitting some visceral motor fibers these are parasympathetic fibers to the plexus
as we look adjacent to the carotid sheath so the cervical sympathetic trunk is typically found
a little posterior medial to the sheath we can see the superior cervical ganglion of the
cervical sympathetic trunk there's the middle and the inferior that superior cervical
ganglion is going to provide postganglionic parasympathetic i'm sorry postganglionic
sympathetic fibers to the plexus these are going to be vasomotor so they're going to
find their way into the walls of the vasculature
that are will supply this plexus and when we talk about the targets of the plexus it's probably good
to know that this is going to include both the pharynx as well as the soft palate which is
very anatomically close to the pharynx as you may recall from sagittal views of these structures
now the pharyngeal neural plexus is going to innervate most of the muscles and mucosa of the
pharynx the great exceptions to these include the stylopharyngeus muscle that stylopharyngeus muscle
is not innervated by the pharyngeal plexus it is innervated solely by the glossopharyngeal nerve
and their close anatomical relationship should demonstrate that to you another exception is the
nasopharynx if you can imagine that nasopharynx is going to be deep anteriorly there the pharyngeal
plexus never gets to it it's innervated by a branch of the maxillary division of the
trigeminal nerve or v2 for short called the pharyngeal nerve the pharyngeal neural plexus
also is going to innervate most of the muscles and the mucosa of the soft palate an exception to this
is one of the soft palate muscles called the tensor veli pelletini which is innervated by a
branch of the mandibular nerve or v3 for short called the nerve to the medial pterygoid now
when we think of the function of the pharyngeal plexus beyond the obvious you know motor with
regards to swallowing and sensory for detecting stimulation for triggering the digletician reflex
there's also an opportunity for another reflex known as the pharyngeal or the gag reflex this is
a protective reflex that clamps down the pharynx to prevent any foreign bodies that are unexpected
from traveling more distally so how this works is a stimulus touches the mucosa of the pharynx
that is transmitted back to the cns in the brain through the glossopharyngeal nerve and the brain
sends out a response via the vagus nerve and that response is to clamp down you know it as a
a gagging now the literature is pretty sparse on this but about one third of the population will
have a gag reflex one-third will not have a gag reflex and one-third of the population will have
a hyper gag reflex which may include emesis or vomiting so we've discussed the pharyngeal neural
plexus the inputs and the targets this is your summary slide thank you very much for your time