With the posterior laryngeal pharynx split open and the mucous membrane removed, examine the posterior aspect of the larynx. Identify the free posterior borders of the thyroid cartilage. Look somewhat inferior to the thyroid cartilage and find the large posterior aspect of the cricoid cartilage. Arising from the midline of the posterior cricoid cartilage and traveling in a lateral and superior direction to the arytenoid cartilage, is the posterior cricoarytenoid muscle.

Gently pull one side of the thyroid cartilage away from the cricoid cartilage, to see the lateral cricoarytenoid muscle between these two cartilages as it descends anterior and inferior away from the arytenoid cartilage.

Superior to the posterior cricoarytenoid and running transversely between the two arytenoid cartilages, you should be able to see the fibers of the small arytenoid muscle. Can you understand how these three muscles act to rotate and glide the arytenoid cartilage and thus control the size of the opening between the opposing vocal folds? On the anterior aspect of the thyroid cartilage, see if you can locate the "bow tie" shaped cricothyroid muscle. This muscle acts on the cricothyroid joint by tilting the thyroid cartilage anterior like a visor on a helmet. This anterior tilting of the thyroid cartilage increases the tension of the vocal cords and increases the pitch of your voice.

The vagus nerve supplies the larynx with motor and sensory innervation by the superior laryngeal nerve and its two branches the internal and external laryngeal nerves , as well as the recurrent laryngeal nerve.

The superior laryngeal nerve leaves the vagus nerve superior to the level of the hyoid bone and lies on the lateral surface of the middle and inferior constrictor muscles. On the lateral surface of the inferior constrictor muscle the superior laryngeal nerve splits into the internal and external laryngeal nerve. Find the internal laryngeal nerve entering the larynx through the thyrohyoid membrane. It provides sensory innervation to the larynx above the vocal cords.

Now find the other branch of the superior laryngeal nerve, the external laryngeal nerve as it runs more inferior to the cricothyroid muscle.

The recurrent laryngeal nerves can be seen in the sulcus between the trachea and esophagus running superiorly towards the larynx and posterior to the thyroid gland. The recurrent laryngeal nerves provide motor innervation to all the intrinsic muscles of the larynx except the cricothyroid. Can you see how thyroidectomies could damage recurrent laryngeal nerves?

With the posterior wall of the larynx split, look on the internal lateral wall of the larynx and find the more superior vestibular folds (false vocal cords) and the more inferior true vocal folds (cords). In between these two folds, find the laterally projecting compartment, the ventricle of the larynx.