Oh hello and welcome to this video covering the innovation of the intrinsic muscles of the larynx let's start with the relevant anatomy we have the hyoid bone at the top colored in in a kind of gold color we have in blue the thyroid cartilage we have the cricoid cartilage as well and we also have the trachea there's a membrane that stretches between the hyoid bone and the thyroid cartilage called the thyrohyoid membrane so we can't see the vocal cords inside all the vocal folds but they're in there and we're going to talk about the innovation to some of the muscles that move the vocal cords and we can summarize that by saying that in actual fact all of the innovation to the vocal cords is from the vagus nerve but it's from a number of different branches first of all let's just cover the vagus nerve the vagus nerve is on the left and the right side of the neck and the fibers here originate from the inferior vagal ganglia high up in the neck on each side and they descend the vagus nerves medial to the internal carotid artery and divide into a couple of branches so first of all we've got the recurrent laryngeal nerves which are branches of the vagus and we have one of those on the left and the right side it's worth bearing in mind that they have slightly different courses on the left and the right side with the left one dipping down lower around the arch of the aorta while on the right side the recurrent laryngeal nerve comes around the subclavian artery the other major nerve here is the superior laryngeal nerve so the two main nerves the recurrent laryngeal nerves and the superior laryngeal nerves now the superior laryngeal nerve divides into two further branches the internal branch and the external branch so in summary we have two branches that supplies the intrinsic muscles of the larynx the recurrent laryngeal nerves the superior laryngeal nerve which is further divided into an internal branch and an external branch so how does the innovation work then well let's take a look now at the functions of each of these we're going to start off by talking about the external branch of the superior laryngeal nerve now this supplies the cricothyroid muscle only so only supplies one muscle it's motor to the cricothyroid muscle the internal branch of the superior laryngeal nerve is mainly sensory and it supplies sensory innervation to above the vocal folds so its main job is sensory to areas of the larynx above the vocal folds let's move on now and talk about the innovation of the recurrent laryngeal nerve the other main nerve here involved in the innovation of the intrinsic muscles of the larynx the recurrent laryngeal nerve on each side runs in the trachea or suffered a groove and runs all the way up each side of the trachea in order to penetrate deep inside the larynx to supply all of the muscles in there except for the cricothyroid muscle which is of course supplied by the external branch of the superior laryngeal nerve it also has a sensory function being sensory to below the level of the vocal folds so a dual role therefore the recurrent laryngeal nerve it has a sensory function below the folds but it also innovates all of the muscles except for cricothyroid subscribe to Soton brain hub for more videos to help explain the mysteries of the brain