Anatomy

The larynx is part of the upper respiratory tract and connects the nasal and pharyngeal air passages to the trachea. It is lined with ciliated columnar epithelium for the most part but some areas – especially the vocal cords or folds – are lined with a tougher keratinised squamous epithelium. The larynx is made up of a series of cartilages joined by membranes and muscles and contains the vocal cords (Figures 31.1 and 31.2). The largest cartilage in the larynx is the thyroid cartilage, which is divided into a left and right lamina. These joint at the front like the keel of a ship and at the uppermost point form the laryngeal prominence or Adam’s apple. The thyroid cartilage acts as protection for the vocal cords. Between the thyroid cartilage and the first tracheal ring is the cricoid cartilage. This is a signet ring shaped structure and is the only complete ring in the airway. This is the narrowest point of the upper airway in children whereas the level of the vocal cords is the narrowest point in the adult upper airway. The cricoid cartilage articulates with the thyroid cartilage as well as smaller cartilages within the larynx to allow vocal cord movement and hence voice production. The larynx is attached to the hyoid bone by muscles and membranes which in turn suspend the hyoid bone from the mandible. The muscles that attach to the external part of the larynx elevate and depress the organ during speech and swallowing, these are termed the strap muscles.

Nerve Supply 

The nerves that supply the muscles of the larynx are the superior and recurrent laryngeal nerves. Both are branches of the vagus nerve (Figure 31.3). The recurrent laryngeal nerve branches off the main trunk of the vagus, loops round the aortic arch on the left and the subclavian artery on the right (hence the name recurrent

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