Figure 2-8
Lobes of right and left lungs with associated airways.

Each lung is divided into a superior and inferior lobe by an oblique fissure. The superior lobe of the right lung is further subdivided by a horizontal fissure which produces a small anterior middle lobe. Therefore the left lung has two lobes and the right lung has three lobes.

The root of the lung is comprised of the primary bronchi, the pulmonary arteries and the pulmonary veins.

The trachea splits into two primary bronchi at about the fourth thoracic vertebral level. The right primary bronchus continues in nearly a vertical line, while the left primary bronchus veers laterally. For this reason, aspirated objects usually end up in the right bronchus and right lung. Each primary bronchus further subdivides into secondary or lobar bronchi that serve the separate lobes of each lung. (Figure 2-8)