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Dr. P here talking about the 9th cranial

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glossopharyngeal nerve.

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I want you to remember three components as we talk about

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the real origin in the medulla oblongata

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of the glossopharyngeal nerve,

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and they are the nucleus ambiguus,

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the inferior salivary nucleus, and the solitary tract nucleus.

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So, let's see where we are.

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We're at the level of the restiform body.

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Just for giggles, let's mark something we all know.

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We'll mark it in red.

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It's a motor pathway,

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just to get the motor pathway set.

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And this is known as the pyramid.

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And then we have the anterior midline sulcus

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between the two pyramids.

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So now we've got a couple of other,

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what I call motor pathways,

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that participate in the motor supply

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of the glossopharyngeal nerve.

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First, we've got the nucleus ambiguus,

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which is kind of right off the midline,

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a little bit behind center.

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Then we've got,

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and I've drawn it a little bigger

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than it really is, just so you can see it.

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Then you've got more posteriorly,

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just under the fourth ventricle,

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the nucleus of the solitary tract.

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That's also going to give rise to some motor function.

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And now let's switch over to some other color

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that represents a sensory contribution,

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which is the nucleus of the solitary tract,

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which sits just lateral to the inferior salivary nucleus.

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And now we have it.

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So now if we draw the apparent origin,

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we've got the sensory,

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and then we've got the contribution

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of the motor right here.

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These two give rise to the motor component

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of the trigeminal...

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sorry,

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of the glossopharyngeal as they come out.

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And they sort of travel together as one.

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You really can't separate them out.

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I've just separated them out anatomically for

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your perusal and educational interest.

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Now, the motor fibers arise in the medulla oblongata

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at the upper part of the nucleus ambiguus,

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which, by the way,

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receives central fibers from the precentral gyrus

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via the corticonuclear tract.

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They begin their course in the back,

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medially and down toward the floor

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of the fourth ventricle.

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But they swerve pretty sharply to the side

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before merging with the sensory roots.

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And you can see that sharp lateral swerve.

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And then the sensory root comes together with the motor

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root to produce the glossopharyngeal nerve,

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the real origin of the glossopharyngeal nerve,

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sensory and motor at the medulla oblongata,

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remembering the three major components:

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nucleus ambiguous, inferior salivary nucleus,

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nucleus of the solitary tract.

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Dr. P out.