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Dr. P here talking about the hypoglossal nerve,

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as you saw in the last vignette.

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This nerve will penetrate the lateral mass of

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the occipital bone as the hypoglossal canal.

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To see the canal,

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you have to go down and a little bit lateral,

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which we'll do in a minute.

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There's the hypoglossal nerve.

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But I want to clarify one thing.

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There's a little bump right here which is actually

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the pyramidal bump. And behind that,

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if we scroll a little bit up and down,

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you can see a second little bump.

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There's your second little bump, the olive.

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So this is going to be a preolivary position of the

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hypoglossal nerve, whereas nine and ten are

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going to have more of a postolivary,

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more posterior position as you saw on earlier vignettes.

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Then as we scroll down,

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we lose the nerve for a little bit.

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Kind of gets buried and hidden by the pulsation

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phenomenon and anatomy of the vertebral artery.

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But there is our hypoglossal canal

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with an anterolateral course.

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We said there are multiple rootlets that converge into

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one nerve, sometimes two nerves traveling together.

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But no more than two trunks,

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as what you see with the hypoglossal nerve.

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Now, the hypoglossal nerve passes through

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the subarachnoid space.

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It passes the dura mater in the hypoglossal canal and in

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the opening of the occipital bone, as we described.

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But after emerging, it gives off a meningeal branch.

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It picks up a branch from the anterior ramus of C1.

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And you can start to see those branches

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as we scroll downward right here.

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Here are some of the branches down lower

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of the upper cervical region, C1.

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And then it travels close to the vagus nerve and spinal

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division of the accessory nerve, spiraling downward behind

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the vagus nerve and passes between the internal carotid

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artery and the internal jugular vein,

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lying on the carotid sheath.

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So, it's going to sit as you would expect because

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twelve comes after ten and eleven.

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It's going to sit behind the vagus nerve as it descends.

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Dr. P out.