Surgical anatomy

Tracheobronchial tree

The bony skeleton of the larynx consists of the hyoid bone superiorly, and the thyroid and cricoid cartilages, from which the trachea is suspended. The thickened edge of the cricovocal membrane forms the cricovocal ligament, which is covered with mucous membrane and thus forms the vocal fold (cord). The vocal cord is responsible not only for phonation, but also for protection of the tracheobronchial tree from food and fluids during deglutition. The nerve supply of the vocal cords is largely by the recurrent laryngeal nerves, which originate from the vagus nerve within the thorax. On the right side the recurrent laryngeal nerve originates in the root of the neck, hooks around the right subclavian artery and ascends to the larynx between the trachea and oesophagus. On the left it originates at the level of the aortic arch in the thorax, hooks around the ligamentum arteriosum, and ascends to the right of the aortic arch, again between the trachea and oesophagus. Thus the left recurrent laryngeal nerve in particular is susceptible to involvement by mediastinal pathology.

The laryngeal prominence (Adam's apple) is formed by the junction of the two laminae of the thyroid cartilage. Below this is the cricoid cartilage, and between the two is the cricothyroid membrane which is the landmark used for emergency cricothyroidotomy or more commonly, the insertion of a minitracheostomy (Figure 19.1).