Vagus Nerve - Cranial Nerve X travels in the carotid sheath deep to the common carotid artery and internal jugular vein.  The vagus has a wide array of innervation in the head and neck as well as throughout the chest and abdomen.  The superior laryngeal nerve arises from the vagus and travels inferior-medially.  Two branches are significant; the internal laryngeal nerve and the external laryngeal nerve.  The internal laryngeal nerve pierces the thyrohyoid membrane with the superior laryngeal artery and is sensory to the laryngeal mucosa above the vocal folds.  The external laryngeal nerve is a motor nerve to cricothyroid.  There is an additional motor branch to the larynx in the recurrent laryngeal nerve which is a motor nerve to the laryngeal muscles and carries a sensory component to the laryngeal mucosa below the vocal folds.  This nerve may be seen ascending along the lateral border of the thyroid and entering the larynx.  Further detail will be given to this nerve later.  Reference Netter Plates 27, 65, 69, and 70.