Right Pulmonary Arteries

1. Right Upper Lobe

The first branch of the right pulmonary artery is called the truncus anterior; after the takeoff of this vessel, the descending portion of the pulmonary artery is called the interlobar artery, as it lies in the interlobar fissure. The truncus anterior usually begins as a single artery that courses superiorly anterior to

Table 1 Boyden's Numbering System for Segmental Anatomy of the Lung

Boyden

Name of Right Lung

Name of Left Lung

Number

Segmental Artery

Segmental Artery

Right upper lobe

Left upper lobe

A1

Apical Segment Artery

Apical Artery (to the Apical-

posterior segment)

A2

Anterior Segment Artery

Anterior Segment Artery

A3

Posterior Segment Artery

Posterior Artery (to the Apical-

posterior segment)

A4

Right middle lobe

Lateral Segment Artery

Superior Segment Lingular Ar-

A5

tery

Medial Segment Artery

Inferior Segment Lingular Ar-

tery

A6

Right lower lobe

Left lower lobe

A7+8

Superior Segment Artery

Superior Segment Artery

Anteromedial Basal Segment

A7

Artery

A8

Medial Basal Segment Artery

Medial Subsegment Artery

A9

Anterior Basal Segment Artery

Anterior Subsegment Artery

A10

Lateral Basal Segment Artery

Lateral Basal Segment Artery

Posterior Basal Segment Artery

Posterior Basal Segment Artery

The numbering system described above applies exactly only if the bronchi and the arteries are precisely parallel, an uncommon scenario. If segments are supplied by arteries that do not directly parallel the bronchi, each artery derives its name from the bronchial segment it supplies. So, for example, a right middle lobe artery may bifurcate into an artery that supplies only a portion of the lateral segment, B4, and a second artery that supplies the remainder of the lateral segment and the medial segment, B5. In this case, the first artery is called A4a, and the second artery is called A5+4b. The two major branches of a numbered artery are called a and b, for example, A3a and A3b.

The numbering system described above applies exactly only if the bronchi and the arteries are precisely parallel, an uncommon scenario. If segments are supplied by arteries that do not directly parallel the bronchi, each artery derives its name from the bronchial segment it supplies. So, for example, a right middle lobe artery may bifurcate into an artery that supplies only a portion of the lateral segment, B4, and a second artery that supplies the remainder of the lateral segment and the medial segment, B5. In this case, the first artery is called A4a, and the second artery is called A5+4b. The two major branches of a numbered artery are called a and b, for example, A3a and A3b.

the right main bronchus. This most commonly divides into an anterior segmental branch (Fig. 1D) and an upper branch. The upper branch usually divides into apical and posterior segmental branches (Fig. 1C). However, there is commonly a branch from the interlobar pulmonary artery to the posterior segment of the upper lobe and sometimes a branch to the apical segment.

2. Right Middle Lobe

Approximately half of the time, two right middle lobe arteries arise from a common trunk from the right interlobar pulmonary artery, and about half of the time they arise as two separate branches of the interlobar artery (Figs. 1G and 1H). A branch of the medial segmental artery most frequently supplies the anterior aspect of the lateral segment.

Figure 1 Examples are taken from two different patients. (A) Apical segmental artery, LUL. Unlike the common apicoposterior segmental bronchus, this artery frequently has an origin separate from the posterior segmental artery.

Figure 1 Examples are taken from two different patients. (A) Apical segmental artery, LUL. Unlike the common apicoposterior segmental bronchus, this artery frequently has an origin separate from the posterior segmental artery.

3. Right Lower Lobe

Below the origin of the right middle lobe artery or arteries, the interlobar artery becomes the right lower lobe artery. It usually then gives off one or occasionally two posteriorly directed arteries to the superior segment of the right lower lobe (Fig. 1G). This is usually at the same level as, or slightly caudal to, the takeoff of the right middle lobe bronchus. The name of the artery beyond the origin of the superior segmental artery is the pars basalis or basal artery or trunk (Fig. 1H), and this gives off the basal segmental arteries. In slightly more than half of cases, the medial basal segmental artery arises first or arises first as a common trunk with the anterior segmental artery— this representing a very variable artery (Fig. 1J). Finally, the lateral basal and posterior basal arteries arise independently or bifurcate from a common trunk, again with significant variability (Fig. 1K).

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