Our lecturer is very adamant that the recurrent laryngeal is in fact the cranial root of accessory nerve, which is correct. Why then do most textbooks have it as a branch of vagus? Granted, the fibres are carried along with vagus, but as my lecturer said, you can actually separate the vagus from the recurrent laryngeal long before it branches.
Recurrent laryngeal branch of vagus?
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The nucleus ambiguus (X) is the source of motor efferents to the larynx/ pharynx, isn't it? The ability to differentiate might be because the path from the dorsal nucleus of the vagus is the separate origin of all preganglionic parasympathetics to structures below the heart and above the left colic flexure, so you could theoretically trace the 2 efferent axonal tracts of the vagus back to distinct origins in vagal nuclei.
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Well then you've stumped me (which isn't a great feat)
Yeah that's what I remember too, I just never knew/heard that it was from XI (rather than X). I might have just gotten the watered-down story though as an MS1...
Gray's anatomy disagrees with you there...["distribution: motor to muscles of soft palate and intrinsic muscles of the larynx (via the vagus)"]. I assume that this is the same as C1 via hypoglossal. It will still be supplied by the accessory but the nerve fibres "hitckhike" with the vagus. We are using clinically oriented anatomy as our prescribed book though, and that is where I found that it was a branch of vagus. Our lecturers told us to correct it. So really just wondering where the branch of vagus comes from...[My lecturer would say that Moore just doesn't know his embryology well enough]
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Maybe you should bring this discrepancy up to the lecturer and see if he/she can clarify. It seems odd that all textbooks would say something different from what 1 teacher is teaching.
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What Gray's is saying is correct and agrees with what i said earlier. The Recurrent laryngeal nerve is a branch off the Vagus N. (not the Accessory N.) as it makes its way down the mediastinum and into the abdomen. The recurrent laryngeal nerve will supply all intrinsic muscles of the larynx, with the exception of the cricothryoid muscle (supplied by the external branch of the superior laryngeal nerve, which is also a branch of Vagus) and sensory to mucosa below the vocal folds.
Does that help?
Saying that it is a branch of something is assuming that some of the fibres are coming from the root of the vagus, that is where my problem lies.
I agree with how you come up with your branch, because I have seen it in a cadaver, my point is just, is it really a branch or does it merely travel with vagus?
I agree with how you come up with your branch, because I have seen it in a cadaver, my point is just, is it really a branch or does it merely travel with vagus?
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I dont understand what you are looking for. .
The teacher is the only one who will be able to explain the rationale behind what they taught in the class. If they say the textbook is wrong, then you're going to have to go with that.
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From "Neuroanatomy Text and Atlas" ,Martin, 3rd ed
"The most caudal portion of the nucleus ambiguus contains laryngeal motor neurons whose axons course in a portion of the spinal accessory (XI) nerve. This cranial nerve consists of distinct cranial and spinal roots, and only axons in the cranial root have their cell bodies in the nucleus ambiguus. These axons are probably displaced vagal fibers that join the vagus nerve as they exit the cranium and then innervate the same structures as the vagus."
Emphases are the authors.
Seems somewhat pedantic as everyone is clear on where it is just not on what to call it.
D
da8s0859q
Because your lecturer is being pedantic.
CN XI has two roots: cranial and spinal. The cranial root contributes function to CN X; the spinal root is what's responsible for innervating the SCM and trapezius mm., like we think of CN XI.
Your lecturer is right -- yeah, the cranial root does run with the vagus and can be separated at some point, I'm sure -- but functionally speaking, it does what the vagus does, and ultimately combines with the vagus, so we think of it as part of the vagus nerve.
It was explicitly taught like that at my school.
As far as destroying the motor nucleus of CN X... remember that the nucleus ambiguus is thought of as the motor nucleus for that nerve, and that the cranial portion of CN XI originates from there as well. No matter how you look at it, if you destroy that nucleus, your larynx is screwed.
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Well, let's just drop the pretense. We all know that CN XI is a poser anyway. 😎 hiding behind those initials and that roman numeral as if it were an actual cranial nerve.
AS IF!
I say, we call it "Spinal Nerve #1".
My textbook addendum will hit the shelves this August. Look for it at an overpriced bookstore nearest you.
AS IF!
I say, we call it "Spinal Nerve #1".
My textbook addendum will hit the shelves this August. Look for it at an overpriced bookstore nearest you.
Can't this all just be a matter of semantics? Think of the nerves as two highways that follow the same road for a while... say... I-43 and US-41. They meet up around Chicago, run together for a while before US-41 "branches" off I-43 around Green Bay. Does that make I-43 and US-41 the same, or insinuate that they have common origin? No. But US-41 could still be considered a "branch" off I-43.
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The OP is in school outside the US so i dont think US boards are an issue. He/she just need to learn it the way the teacher taught it to make it through that course.
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From what I recall, we were taught that there is no cranial root of CN XI, and its all spinal and just innervates the SCM and trapezius. What they used to think was the cranial root of XI is just part of the Vagus.
Which means that CN XI isn't properly a cranial nerve, but they wont rename it because that just ends up confusing.
Which means that CN XI isn't properly a cranial nerve, but they wont rename it because that just ends up confusing.
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I recall reading a text where the author stated (paraphrased): careful recent studies have proven that there is no cranial root to CNXI. I think it may have been Nolte but don't quote me on that. It may have been in the Haines atlas??
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This distinction--that the nerve is called recurrent laryngeal before it enters the larynx and inferior laryngeal once it enters the larynx/laryngeal cartilage--is not an important point. Surgeons/physicians don't use that dichotomy--it's recurrent laryngeal no matter where the nerve is. The distinction is only important to anatomists.
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Yep, this is right. CN XI was (and often still is) called the Accessory Nerve. Most comes from the spinal cord, but it appeared a small porition came from the brain--hence it's designation as a cranial nerve. However because the (small) cranial porition appears to come from the vagus, the nerve is now called the Spinal Accessory Nerve. Look at the wikipedia page.
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Mind boggling.
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Spine boggling. imo
