The Functions of the Larynx

Matthew Reeve

The larynx is often described as the voice box. This label can be misleading as the larynx is not only a source of vocal sounds but it also has several other biological functions that are vital to survival. Knowledge and understanding of these functions help vocalists to use their voices safely and skilfully.

• Protection of the airways. The need to keep the airways free from obstruction is paramount to survival. This is considered the primary function of the larynx. The true vocal folds, false vocal folds and epiglottis act together as a sphincter to form a barrier that prevents food and foreign bodies entering the trachea and impeding respiration. A demonstration of the importance of this primary function is seen in there being three sets of muscles in place to close and tense the true vocal folds but only one set to open. The larynx reacts violently when stimulated by foreign objects consider how the body responds when food goes down the wrong way. This is a natural reflex and happens as part of swallowing.
• Pressure valving. The ability to control pressure in the thoracic cavity is important for the efficiency of bodily functions. These include going to the toilet, childbirth and the ability to secure the thoracic cavity when lifting heaving objects. In pressure valving larynx closure helps to stabilise the upper body, providing a solid framework for strenuous muscular effort. Do the following and notice what can happen at the larynx: sit on a chair and raise your feet off the ground; then, whilst seated, inhale and try lifting yourself and the chair off the ground. You feel a sense of closure at the larynx as the physical effort is exerted.
• Phonation. On the biological survival scale, phonation is considered a tertiary function. Like with other mammals, the larynx has evolved to assist with noise-making. The larynx is designed to enable crying and shouting with ease a baby can cry loud and long. Human larynxes have descended lower in the vocal tract compared to other mammals; this has facilitated more complex communication patterns. Singers and speakers capitalise on the phonatory ability of the larynx with complex linguistic tasks such as speech and song.

The protective instincts of the larynx are easily triggered; they are wired into our flight and fight responses. Two of the natural functions of the larynx are reflex actions that involve constriction of the laryngeal structures, that is closure of the airway. For instance, if something goes wrong in a rehearsal and we get upset or angry, the protective reflex can be triggered, and the larynx may constrict. This will clearly impede on vocal function. Active measures are needed to counteract what is biologically normal when singing or speaking in stressful situations.

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