hello anatomy friends this is dr alsup and in this video we will be discussing the
parasympathetic innervation of the submandibular gland and its close neighbor the sublingual glands
and all those smaller salivary glands in the oral cavity region so those are salivary glands recall
this discussion will include the source of those preganglionic parasympathetic fibers
so where those are originating from which ganglion so one of those peripheral parasympathetic ganglia
where they will synapse and through what means do those postganglionic fibers reach both the
submandibular and the sublingual glands so that will be the focus of this video today
all right so take a moment and i want you to try to remember which cranial nerve is the
source of the preganglionic parasympathetic fibers destined for the parotid gland so not what we're
going to spend the majority of this video on but review what you know about the protogland
which one of the cranial nerves is going to to innervate that
and hopefully you remember it's the glossopharyngeal nerve or cranial nerve nine
when speaking about the submandibular and sublingual glands the source is not
glossopharyngeal but instead it will be the facial nerve or cranial nerve seven
the facial nerve is another cranial nerve like the glossopharyngeal that is fairly complex
in regards to multiple functions as you can see over here it is actually going to provide
preganglionic parasympathetic fibers to two different types of glands so not just the
submandibular and sublingual glands or the salivary glands but also the lacrimal gland
which is going to produce tears but our focus today will be on those salivary glands
and we are going to go through the steps that are mentioned on this particular chart step by step
and then we'll come back to this chart at the end to kind of review
all right the branch of the facial nerve that will have the pertinent preganglionic parasympathetic
fibers for this session is the chorda tympani love the chorda tympani that is a fun name there are
other fibers within the chorda tympani which so there's going to be preganglionic parasympathetic
fibers and they're going to wrap be wrapped up together with special sensory fibers and these are
going to play a role in terms of the special sense of taste so going to be associated with the tongue
specifically it's going to provide that special sensory innervation to the tongue
anterior to the valet papillae which are specific papillae on the tongue which house taste buds
so similar to what we did with the tympanic nerve
the glossopharyngeal nerve let's follow the parasympathetics to their target organ
the chorda tympani will actually branch from the facial nerve before the bulk of the facial nerve
exits the stylomastoid foramen so to be clear this branch is going to occur within the skull
in the facial canal and from here the chorda tympani will head toward the middle ear region
similar to that tympanic nerve so it does not exit through the stylomastoid foramen it is before that
the chorda tympani will traverse the middle ear and you can see it actually it's i think
this is a pretty cool relationship you can see it traversing between the malleus and
the incus bone so here's your malleus and here is your incus these are two of your
ear ossicles which are the smallest bones of the body so associated with the middle ear
the chorda timpani will make its way through the middle ear and will eventually
exit the cranium of the skull via the petro-tympanic fissure
and the petro-tympanic fissure can be a little tricky to see i always try to
locate that mandibular fossa which you can see here and is this long slit like fissure
that is going to be just posterior to that mandibular fossa
and once this chorda tympani exits through the skull
through the petro-tympanic fissure it will be in what we refer to as the infra temporal fossa
which is a region deep to the masseter muscle so in the deeper portions of the face
the chorda tympani travels a little bit within that infratemporal
so this whole region right here is going to be referred to as the infra-temporal fossa
and it will travel a little bit let me get my bearings here it is it's going to travel
a little bit within the infra-temporal fossa before it will join up with the lingual nerve
as you can see right over here so it's going to kind of dive deep to this and kind of
enter into and join with the lingual nerve the lingual nerve is headed towards the tongue and
the oral cavity region because one of the major functions of the the lingual nerve is to send
sensory signals back to the central nervous system from the anterior portions of the tongue
so really that lingual nerve is covering the same territory as according typically in regards to the
tongue but recall according tympani is going to have special sensory fibers or taste fibers
whereas the lingual nerve is general sensory to the tongue so say if you are pinching your tongue
you cut your tongue those signals are going to be general sensory
so we have that chorda tympani hitchhiking with the lingual nerve
and um those and this whole time those chorda tympani fibers that are parasympathetic
are pre-ganglionic so we've been pre-ganglionic this whole discussion up until now but it will
make its way into this region to synapse in the submandibular ganglion the ganglion will
lie superior anterior to the deep part of the submandibular gland so here's your submandibu
this is deep part of submandibular gland right here uh you can also see it's loosely
associated with the lingual nerve which you can see running right here so kind of medial
to the lingual nerve and this is where those preganglionic parasympathetic fibers will synapse
from the ganglion the postganglionic sympathetic parasympathetic fibers will head to their target
organs of those salivary glands in this region and it will do so either by traveling near the
surrounding vasculature or it may even hitchhike again with the lingual nerve to get to a bit more
distal areas so that is how those postganglionic parasympathetic fibers are getting to the
submandibular gland the sublingual gland and any of those smaller salivary glands in that region
so here is that nice review chart again chorda tympani is going to have those preganglionic
parasympathetic fibers they will make their way through the middle ear and will eventually exit
the skull to get to the infra-temporal fossa where it will join with the lingual nerve
the preganglionic parasympathetic fibers will synapse and the submandibular ganglion and then
the postganglionic parasympathetic fibers will travel the short distance to get to
the sublingual and submandibular glands so easy peasy right as always take it take your own time
to review and focus in on those areas that are a little bit trickier to you then reach out to your
colleagues or of course anatomy faculty and we can discuss from there we're always here to help
all right let's go quickly go through a question here the preganglionic parasympathetic fibers
that will synapse in the submandibular ganglion originate from which cranial nerve
so a few key things in the stem that i hope you are looking at so we're trying to think about
pre-ganglionic parasympathetic fibers they're going to synapse in the submandibular ganglion
and it is a cranial nerve all right so really if you're looking at the answer choices all of these
are cranial nerves so this isn't all that helpful in the stem so let's focus on these two areas
all right which ones of these answer stems have preganglionic parasympathetic fibers associated
well it is not the hypoglossal there are no preganglionic parasympathetic fibers
associated with the hypoglossal nerve so that's not the correct answer
the other four options do have preganglionic parasympathetic fibers so then we're going
to really hone in on which ones are going to synapse in the submandibular ganglion
and hopefully that leads you to a or the facial nerve being the correct answer
the glossopharyngeal parasympathetic fibers will synapse in the otic ganglion so not the
correct answer whereas the oculomotor fibers will synapse in the ciliary ganglion and the
vagus does not does have important preganglionic parasympathetic fibers but they will not synapse
in any of those peripheral parasympathetic ganglia of the head so this should wrap up
wrap us up regarding the parasympathetics in this session thank you for your time and attention