++
The upper airways are defined as the trachea and mainstem bronchi. Functionally, the upper airways serve as conduits for ventilation. Anatomically and physiologically, however, they represent complex structures that are susceptible to a wide variety of processes. Involvement of the trachea, mainstem bronchi, or both in various disease processes, although rare, present challenging problems for both physician and patient.
+++
Anatomy and Physiology
++
The adult human trachea begins at the level of the cricoid cartilage and extends to the bifurcation of the mainstem bronchi (Figs. 53-1 and 53-2). The carinal spur is a useful landmark that denotes the distal extent of the trachea. On average, the adult human trachea measures 11 cm in length, with some variation in proportion to the height of the individual patient. There are approximately two tracheal rings per centimeter of trachea. Thus, on average, the total number of tracheal rings ranges from 18 to 22, with the cricoid forming the only complete tracheal ring. The potential for presentation of the trachea in the neck is a major factor permitting relatively easy surgical access. In a young, nonobese adult, hyperextension of the neck may deliver more than 50% of the trachea into the neck, thereby greatly facilitating any attempt at resection and reconstruction. From a nearly subcutaneous position at the level of the cricoid, the trachea courses posteriorly and caudally at an angle, resting against the esophagus and vertebral column at the level of the carina.
++++++
The blood supply of the trachea is vital to successful resection and reconstruction. The upper trachea is principally supplied by branches of the inferior thyroid artery, whereas the lower trachea is supplied by branches of the bronchial artery as well as by branches of the subclavian, supreme intercostals, internal thoracic, and innominate arteries (Fig. 53-3)1. These vessels supply the trachea through lateral pedicles of tissue, and the longitudinal anastomoses between the vessels are very thin. Excessive disruption of these lateral vessels by circumferential dissection of the trachea may compromise blood supply and lead to complications, such as stenosis and anastomotic dehiscence. At the level of the second and third tracheal rings, the thyroid isthmus crosses the trachea anteriorly. The recurrent laryngeal nerves course in a groove between the trachea and the esophagus (Fig. 53-4). The nerves enter the larynx between the cricoid and thyroid cartilages.
++