Larynx
The larynx is a hollow structure, continuous with and inferior to the pharynx, and attached to the superior portion of the trachea. As the larynx houses the vocal cords, it is commonly known as the voicebox.
The larynx is made of cartilage and ligaments. Three large pieces of cartilage (along with nine smaller pieces) make up the structural framework of the larynx:
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Epiglottis - is the most superior part of the larynx composed of an elongated and flexible piece of elastic cartilage. It is the only piece of cartilage in the larynx with this elastic property. During breathing and speaking, the epiglottis is in a vertical position that permits movement of air through the larynx. By contrast, during swallowing, the epiglottis closes over the opening to the larynx to prevent the entry of food and fluid into the airway.
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Thyroid cartilage - is a large, butterfly-shaped piece of hyaline cartilage. The thyroid cartilage is commonly known as the “Adam’s apple” as increased testosterone levels during male puberty can cause it to grow to become visible on the anterior surface of the neck. It supports and protects the vocal cords which lies posterior to the cartilage.
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Cricoid cartilage - forms the inferior portion of the larynx. It is a complete ring of hyaline cartilage that attaches to the superior trachea.
The hollow inside of the larynx is lined with a mucous membrane. Projecting into this hollow are two pairs of ligaments, known as the vocal folds, found on the lateral walls of the larynx.
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The inferior pair of vocal folds are known as the true vocal folds, or vocal cords, are elastic, and can produce sound when air is moved across them during exhalation.
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The upper pair of vocal folds are also known as the vestibular folds or false vocal cords. They don’t produce sound, but prevent us from choking by closing off the opening into the larynx during swallowing, as a second line of defense to the epiglottis. The contact of the closed false vocal cords by food or fluid, elicits a strong coughing reflex which also acts to clear the airway of any contents other than air.
The primary functions of the larynx include:
- Conducting air into the trachea
- Protecting the airways from the entry of food and fluid
- Production of sound
Figure 1: The key structures of the larynx. The lower images show the isolated larynx from an anterior and sagittal view.