Step I recurrent laryngeal nerve

[unoriginal]

i thought this was a branch of X. HY neuro states it is a branch of XI. The sources that I have found state it is a branch of vagus that innervates all intrinsic muscles of the larynx except the cricothyroid. So is HY just wrong or am I missing something? Thanks

 

[Idiopathic]

while there are early connections between X and XI before they leave the cranium, recurrent laryngeal is most definitely a branch of X

 

[Roy7]

Could someone please expand on this because I'm totally confused too - HY neuro keeps on saying how CNXI innervates all intrinsic muscles of the larynx and CNX innervates the cricothyroid.

Damn laryngeal nerves - they got me all messed up.

 

[UCLAstudent]

The recurrent laryngeal is definitely a branch of X, but it carries with it some fibers from CN XI. So, really, the laryngeal muscles are innervated by fibers from the CN XI nucleus, but since the fibers travel with a branch of the vagus, we say those muscles are innervated by CN X. It's kind of similar to how we say the pupil constrictor muscle is innervated by CN III, when in reality it's the parasympathetic fibers from Edinger-Westphal (and not fibers from the CN III nucleus) that just happen to "hitch a ride" with CN III.

 

[sweatybrain]

Could someone please expand on this because I'm totally confused too - HY neuro keeps on saying how CNXI innervates all intrinsic muscles of the larynx and CNX innervates the cricothyroid.

Damn laryngeal nerves - they got me all messed up.

I took the board mid-may so this is not as fresh in my memory. But from what I remember, the pharyngeal plexus is the one that innervates all the constrictors. The superior laryngeal nerve, a branch of CN X, has two terminal branches: internal and external. The internal is afferent-only and innervates the mucosa above the vocal fold, whereareas the external branch provides motor innervation to the cricothyroid. Below the vocal fold, both sensory and motor innervations are provided by the recurrent larynegal nerve.

hope this helps.

 

[ginger60]

This is why I did not like HY neuro--knowing that CNX may carry some fibers from CNXI that may innervate the larynx is not high yield at all. The boards will definitely not ask something that uncertain, especially in anatomy. For boards purposes, FA has what you need to know for the most part--CNXI innervates 2 muscles, while CNX innervates most of the larynx and pharynx (know the exceptions), does some taste and parasympathetics, and its branches do specific things (as sweatybrain said).
When in doubt, go with FA (taking into account its errata) over HY neuro.