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ANATOMY OF THE TRACHEA

ANATOMIC STRUCTURE

The trachea is an epithelial-lined, semirigid tube that courses from the inferior border of the cricoid cartilage to the carina. The trachea functions as a conduit for ventilation, connecting the mainstem bronchi with the larynx. It is a midline structure, coursing from the superior to middle mediastinum with a slight anterior-to-posterior angle from a lateral view. Approximately half of the trachea lies within the neck and half within the chest. The cervical portion of the trachea increases with extension and decreases with flexion, advancing age, and kyphosis.

The adult trachea measures approximately 12 cm, but is variable in length (range 10–13 cm) depending on patient height and sex. Composed of C-shaped cartilaginous rings (typically 18–22 rings, or nearly 2 rings per cm), the anterior portion of the trachea is relatively inflexible. The rings may be complete, incomplete, or bifid. The posterior part of the trachea is a membranous flat wall connecting the cartilages (creating a D-shape lumen), and is dynamic with inspiration, expiration, and cough (Figure 39–1A).

Figure 39–1

Anterior view of the trachea and adjacent structures. (A) Anatomical structure of the trachea. (B) Anatomical relationships. (C) Blood supply to the trachea, a left anterior view.

The diameter of the trachea varies by body size and sex. In general, the adult male tracheal diameter is 1.8 to 2.3 cm, compared to the female airway, which is slightly smaller (1.4–2.0 cm). The cross section of the trachea may vary according to age or may be affected by an underlying disease process. For example, the juvenile trachea is more circular. Patients with chronic obstructive pulmonary disease (COPD) have a more triangular-shaped trachea. Patients with congenital stenosis of the trachea have completely circular cartilaginous rings, whereas patients with tracheomalacia may have flat or crescent-shaped airways with an elongated membranous portion.

ANATOMIC RELATIONSHIPS

Given the central position of the trachea, it is surrounded by a number of vital structures in the neck and chest. In the neck, the esophagus is positioned leftward, adjacent the trachea, coursing posteriorly at the level of the clavicles, and remains posterior at the level of the carina as it continues to the diaphragmatic hiatus (Figure 39–1B). This intimate anatomic approximation of the trachea and esophagus accounts for the potential development of a fistula between these 2 structures.

Anteriorly and laterally, the thyroid gland is situated in front of the trachea from the level of the cricoid bone to the second or third tracheal rings. The thyroid isthmus is at the midline and each thyroid lobe extends laterally onto the trachea. These 2 organs share a common blood supply from the inferior thyroid artery.

In order to avoid injury, the tracheal surgeon must have an ...

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