This post may be a bit boring in comparison to some of the
others I’ve written for this blog, but I feel that exploring the innervation of the larynx is an essential component to fully understanding
its function. We’ll keep it fairly simple, so don’t worry about getting bogged down
in the details!
In terms of innervation, it’s the vagus nerve (cranial nerve X) doing most of the work in the larynx. As you may or may not know, CNX is a mixed nerve, meaning that it has the ability to give motor, sensory and parasympathetic innervation, which is exactly what it does in the larynx! There are two branches that come off of the main nerve which go to innervate our larynges. They are the superior laryngeal nerve, and the recurrent laryngeal nerve. Take a look at the following diagram to see where they enter the larynx:
In terms of innervation, it’s the vagus nerve (cranial nerve X) doing most of the work in the larynx. As you may or may not know, CNX is a mixed nerve, meaning that it has the ability to give motor, sensory and parasympathetic innervation, which is exactly what it does in the larynx! There are two branches that come off of the main nerve which go to innervate our larynges. They are the superior laryngeal nerve, and the recurrent laryngeal nerve. Take a look at the following diagram to see where they enter the larynx:
Let’s talk about the recurrent laryngeal nerve (RLN) first. You can see that it enters the larynx inferiorly, and that it splits off further into two sub-branches: the internal and external branches. The internal branch of the RLN gives the larynx some of its sensory innervation, especially to the vocal cords and the subglottic region. (1) The external branch of the RLN is important for motor innervation. It innervates all of the intrinsic laryngeal muscles (except for the cricothyroid muscle which is innervated by the superior laryngeal nerve) and will be the one sending signals to make the muscles move. (Which is essential to being able to vocalize!) (1)
Next up is the superior laryngeal nerve (SLN), and from both the name and the diagram above, I hope you all have managed to discern that it enters the larynx superiorly. The SLN gives the larynx most of its sensory innervation, especially in the area above the vocal cords. (2) When you’ve been singing and yelling with your friends at the local karaoke bar for hours on end, this is the nerve that will let you know! In the majority of people, the SLN has three branches - superior, middle, and inferior - and these simply go to different areas in the larynx.
That about sums up everything I wanted to share with you guys in regards to the innervation of the larynx. I wanted to keep it short and sweet in the hopes that you wouldn't be bored to tears. Until next time!
References:
1. Ardito G, Revelli L, D'Alatri L, Lerro V, Guidi ML, Ardito F. Revisited anatomy of the recurrent laryngeal nerves. Am J Surg. 2004 Feb; 187(2):249-53.
2. Sanders I, Mu L. Anatomy of the human internal superior laryngeal nerve. Anat Rec. 1998 Dec; 252(4):646-56.
3. Marieb E, Hoehn K. Human anatomy & physiology. Boston: Pearson; 2013.
