cranial nerve nine or the is one of the more complicated because it has so many different
components it has a motor component which is both somatic and visceral so it goes to skeletal muscle
and smooth muscle it also or a gland actually in this case it's a gland and it has multiple sensory
modalities it has somatic sensory special sensory and visceral sensory and you can see in this image
from the posterior aspect of the the pharynx here is the glossopharyngeal nerve right here and right
here and it's lying along the only muscle that it innervates which is the stylopharyngeus
muscle here in here so the motor component of the glossopharyngeal nerve again it's going to
innervate the stylopharyngeus muscle right here and that is the key to finding this muscle if
you're ever doing it dissection is that you're always looking for the glossopharyngeal to lie
right along that muscle the rest of this muscle if you'll recall if you have not yet watched
the lecture on the vagus nerve this is all of the skeletal muscle that forms the upper part of your
original constrictors it's continuous with the esophagus and it's all innervated by the vagus
there's a visceral or parasympathetic component of the glossopharyngeal nerve and it innervates pair
the parotid gland so when we talked about cranial nerve seven and it's autonomic functions its
cranial nerve seven innervates the sublingual and the submandibular glands even though it goes right
by the parotid gland it doesn't innervate them the glossopharyngeal via jumping over on a couple of
other nerves to get to its target is the is what innervates the parotid gland when it comes to
sensation the glossopharyngeal is also again it's complicated so the somatic part of the somatic
innervation are the somatic modalities carried by the glossopharyngeal are from the posterior or
post Sokol portion of the tongue so it's this part and so remember that five is general sensory for
the front of the tongue and so and nine is general sensory for the posterior part of the tongue it
also innervates part of your external ear and the internal surface of your tympanic membrane
so if you have an earache if there's fluid in the ear and it causes pressure and that that modality
that that sensation is going to be transmitted by the glossopharyngeal nerve there's a special
component a special sensory and that is taste and again that's going to be for this posterior
post Sokol part of the tongue so the posterior one-third taste is cranial nerve nine and remember
that taste for the anterior portion is seven there's also a special sensory part and I put in
this image down here this is your carotid artery here and here and it splits into an internal and
an external component the external carotid artery as you know is the blood supply to your face and
the internal carotid artery contributes a huge portion of the circulation to the brain where
it bifurcates this carotid bifurcation contains two very special sensory apparatus or apparati
there are the carotid body and the carotid sinus these are sensory organs that measure
your blood pressure and your co2 concentration that visceral information about blood pressure
and co2 concentration are carried back to your brainstem by the glossopharyngeal nerve in the
next segment we'll talk about the hypoglossal nerve has and the muscles that it interface