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In the respiratory system, the bronchus connects the trachea to lung parenchyma for gas exchange with the atmosphere. The trachea bifurcates into right and left mainstem bronchi at the carina (T5 vertebrae level). The right mainstem bronchus measures 2.5 cm in length and is shorter, wider, and more vertical than the left counterpart. On bronchoscopy, the right mainstem appears as a more direct continuation of the trachea, thus making the right lung more susceptible to aspiration, foreign body entrapment, and endotracheal tube misplacement. In contrast, the left mainstem bronchus typically measures 5 cm in length and is more angulated and narrower in caliber. Mainstem bronchi divide into lobar bronchi and more distally into segmental bronchi. There are typically 10 bronchopulmonary segments in each lung. Lobar and segmental branches can be organized according to Table 41-1 and Figure 41-1.

TABLE 41-1Lobar and Segmental Branches of the Lung

Segmental anatomy of the lungs and bronchi. (Reproduced with permission from Grippi MA, Elias JA, Fishman JA, Kotloff RM, Pack AI, Senior RM, eds. Fishman’s Pulmonary Diseases and Disorders. 5th ed. New York, NY: McGraw-Hill Education, Inc., 2015: Fig. 30-3.)



The right mainstem initially branches into the right upper lobe bronchus after 2.5 cm. This orifice is directed at a 90° angle and requires maneuvering to visualize. The upper lobe bronchus divides into apical, posterior, and anterior segmental bronchi. The right mainstem bronchus continues past the upper lobe as the bronchus intermedius for another 3 cm and branches into the middle and lower lobe bronchi. The middle lobe bronchus branches into the lateral and medial segmental bronchi, and the lower lobe bronchi separates into the superior (apical), medial basal (cardiac), anterior basal, lateral basal, and posterior basal segmental bronchi. Of note, the superior (apical) segmental bronchi of the right lower lobe is directed posteriorly and is thus prone to aspiration and abscess.


The left mainstem bronchus continues 5 cm from the carina and branches into the upper lobe bronchus to supplies the upper lobe and lingula. Vertically, the upper lobe bronchus separates into the apical, posterior, and anterior segmental bronchi. Due to the vertical angulation, visualization via bronchoscopy is difficult. In contrast, ...

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