Chapter 37

### Anatomic Structure

The adult trachea measures approximately 12 cm but varies anywhere from 10 to 13 cm depending on height and sex. As there is some variability in the length, the anterior portion of the trachea is not subject to tremendous change, for the most part is composed of cartilage, and is C-shaped. The rings maybe complete or bifid. The posterior part of the trachea is also called the membranous portion and is the part of the airway that moves with breathing (Figure 37–1A).

###### Figure 37–1.

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 among men and women. For the most part, the adult male tracheal diameter is 1.8–2.3 cm compared to the female airway, which is 1.4–2.0 cm. Each tracheal ring is about 4-mm high and there are approximately two rings per centimeter of trachea.

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 and more triangular in patients with chronic obstructive pulmonary disease.

### Anatomic Relationships

The trachea is positioned midline in the mediastinum and is surrounded by many vital structures. In the neck, the esophagus lies just left of the airway and then at the level of the clavicles is directly posterior and adherent to it down to the level of the carina (Figure 37–1B). This gives us a better understanding of why tracheoesophageal fistulas occur.

Anteriorly and laterally, the thyroid is situated in front of the trachea from the cricoid bone to the level of the 2nd to 3rd rings. The isthmus is at the midline and the lobes extend laterally onto the trachea. These two organs have common blood supply from the inferior thyroid artery.

The course of the recurrent nerves is very important for the tracheal surgeon. On the right, it comes off the vagus nerve and wraps around the subclavian and traverses superiorly to enter the larynx between the thyroid and cricoid cartilages in order to innervate the intrinsic muscles of the larynx. On the left it comes off the vagus beneath the aortic arch and runs in the tracheoesophageal groove.

In the compact space of the mediastinum, the trachea is also surrounded by the arteries and veins that come off the heart and the aortic arch. The innominate or bracheocephalic artery comes off the aortic arch ...

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