Your Voice Box: The Larynx

The larynx, along with the vocal folds, is part of the phonation system.

The larynx, the housing of the vocal folds, is an acorn-sized protuberance made of cartilage. The male larynx is larger than the female larynx because the male vocal folds are larger.

The male larynx is also formed at a sharper angle than the female larynx; it is a 90-degree angle, while the female larynx is a softer 120-degree angle.

The larynx is moveable and is affected by the action of the extrinsic swallowing muscles of the neck surrounding it. When we swallow, the larynx is pulled upward by those extrinsic muscles.

When we sing, those muscles should not engage; the larynx should be comfortably neutral and relaxed.

Most singers unknowingly engage extrinsic muscle and hike the larynx as they approach the top notes of the lower register unless they have learned how to transition through the primo passaggio or first bridge correctly.

THE HYOID BONE

The larynx is suspended from the hyoid bone, which helps to determine laryngeal positioning. The hyoid bone is shaped like a shoehorn and is the only bone in the body that does not attach to another bone.

When singing, there should always be space between the thyroid cartilage and the hyoid bone. The hyoid bone connects to the base of the tongue; tongue tension and position can therefore greatly affect laryngeal functioning and position.

During swallowing, the hyoid bone elevates as the extrinsic swallowing muscles activate, pulling the larynx upward with it to guard the entrance of the airway against food and liquid. This swallowing action is what singers must avoid when singing.

THE CARTILAGES OF THE LARYNX

The larynx is made of cartilage, which is harder than muscle tissue, but more flexible than bone. Each cartilage has a muscle attached to it; those muscles are named after the cartilage they originate and terminate with.

The cartilages we will be addressing are:

• The epiglottis
• The thyroid cartilage
• The cricoid cartilage
• The arytenoid cartilages

THE EPIGLOTTIS

The epiglottis is a leaf-shaped cartilage attached to the inside of the thyroid cartilage. The epiglottis has two surfaces, a lingual (tongue) and a laryngeal (larynx) surface.

In the image below you can see the epiglottis peeking out over the top of the hyoid bone. This is the position it assumes during respiration and singing. It lifts to allow air to pass through.

The epiglottis has an important job; it guards the entrance of the glottis, the opening between the vocal folds. During swallowing, elevation of the hyoid bone draws the larynx upward.

The epiglottis folds down to a horizontal position over the trachea (the air tube) to prevent food from going into the trachea, directing it instead to the esophagus (the food tube).

THE THYROID CARTILAGE

The thyroid cartilage serves to protect the vocal folds located directly behind it. This cartilage rests on a flexible hinge called the cricothyroid joint. The thyroid cartilage is the attachment point for several laryngeal muscles. The thyroid cartilage is open in the back and connects with a ridge in the front; this ridge is the bump we call the Adam’s Apple, based on folklore that tells of Adam swallowing an apple that got stuck in his larynx, causing a protrusion.

The vocal folds are positioned just behind the tip of the thyroid cartilage, suspended over the trachea and attached to the arytenoid cartilages at the back of the larynx.

When the cricothyroid muscle contracts, it draws the thyroid and cricoid cartilages toward each other.  The thyroid cartilage tilts forward and down, lengthening and tensing the vocal folds.

THE CRICOID CARTILAGE

The cricoid cartilage (from the Greek krikoeides meaning ring-shaped) sits just below the thyroid cartilage, connected to the thyroid cartilage by the cricothyroid joint. The cricoid cartilage surrounds the trachea, providing an attachment point for various muscles, cartilages, and ligaments.

Because the posterior or back section is broader than the anterior or front section, it resembles a signet ring.

As the thyroid cartilage tilts downward, the vocal folds lengthen and thin because they are attached at the back of the larynx to the arytenoid cartilages, seated on top of the cricoid cartilage.

THE ARYTENOID CARTILAGES

The arytenoid cartilages are two wedge or pyramid-shaped cartilages located at the posterior, or back, of the larynx. They are mounted on the cricoid cartilage and attached to the back of the vocal folds. The arytenoid cartilages are moveable; they approximate, gliding and rotating due to the contraction of the lateral cricoarytenoid (LCA) and interarytenoid (IA) muscles.

When they approximate, they bring the vocal folds along, a bit like closing a set of curtains. This lines the vocal folds up at the midline where they resist subglottal air pressure. This is called adduction or approximation.  When a breath is taken, the arytenoid cartilages recede away from each other in a gliding movement, bringing the attached vocal folds as they glide. This is called abduction.

In the image below, you can see the arytenoid cartilages abducted for inhalation and adducted or approximated for phonation. Notice how they rotate and pivot as they are drawn together; this is the action that brings the attached folds together, creating medial compression.

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