Dissection of the Larynx
This chapter provides a dissection of the larynx using an “outside-in” approach. To begin, a whole-mount larynx specimen is mounted. Layer by layer, structures are identified and removed to discover critical relationships.
Stepwise Procedure
Place the trachea over a cork.
Secure the specimen by placing one pin in each quadrant through the trachea into the cork. Place the cork in the circular holder and tighten the holder around the cork.
Mount the larynx to achieve a left lateral view.
Tie one suture to the base of tongue and another suture to the posterior portion of the left hyoid bone. Wrap the free ends of the suture around the pole of the laryngeal dissection station.
Identify the individual strap muscles. Branches of the ansa cervicalis nerve are seen innervating each of the strap muscles (see Chapter 2’s Fig. 2.4a,b ).
OR Pearl: The ansa cervicalis nerve is formed from contributions of the C1–C3 nerve rootlets. It is part of the cervical plexus. These motor nerves are often used in reinnervation procedures of the larynx.
The sternohyoid muscle is the most medial strap muscle. Trim this muscle with scissors to reveal the cricothyroid muscle ( Fig. 3.1a,b ).
Remove the thryohyoid muscle and sternohyoid muscle. Identify the thyrohyoid membrane. The superior laryngeal neurovascular bundle is seen penetrating the thyrohyoid membrane. The bundle is made of the internal branch of the superior laryngeal nerve (iSLN), the superior laryngeal artery and the superior laryngeal vein.
The external branch of the superior laryngeal nerve (eSLN) is seen innervating the cricothyroid muscle ( Fig. 3.2a,b ). Inferiorly, identify the recurrent laryngeal nerve (RLN).
OR Pearl: The superior laryngeal nerve (SLN) branches into external and internal branches. The internal branch of the SLN is responsible for sensory innervation of the supraglottis. The external branch of the SLN is a motor nerve that innervates the cricothyroid muscle. This is the only intrinsic muscle of the larynx not innervated by the RLN.
OR Pearl: The RLN travels in the tracheoesophageal groove before entering the larynx. The RLN innervates the remainder of the intrinsic laryngeal muscles and provides sensation to the glottis and subglottis.
Examine the anterior surface of the larynx. Identify the thyrohyoid membrane and the cricothyroid membrane (see Chapter 2’s Fig. 2.3a,b ).
Make a horizontal cut superior to the thyroid cartilage through the thyrohyoid membrane to remove the hyoid bone from the larynx. Preserve the epiglottis internally. Place sutures through the thyroid ala laterally to suspend the thyroid cartilage ( Fig. 3.3 ).
Perform the following maneuvers on only one half of the larynx.
Identify the sternothyroid and thyrohyoid muscles’ inferior attachment to the thyroid cartilage ( Fig. 3.4 ).
The larynx is suspended with sutures placed through the thyroid ala. 
Forceps are grasping the superior cut edge of the thyrohyoid muscle.
Remove these muscles to identify the oblique line on the thyroid cartilage ( Fig. 3.5 ).
Identify the cricothyroid muscle. Clean the investing fascia off this muscle ( Fig. 3.6 ).
The oblique line is seen traversing between the superior thyroid tubercle and the inferior thyroid tubercle. (From THIEME Atlas of Anatomy, Neck and Internal Organs, © Thieme 2010. Illustration by Markus Voll.) 
Forceps are grasping the investing fascia of the cricothyroid muscle.
OR Pearl: The cricothyroid muscle has two bellies. The oblique portion originates on the lateral aspect of the cricoid cartilage and inserts into the inferior aspect of the thyroid cartilage, including the inferior tubercle ( Fig. 3.7 ).
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