Configurations of the segmental and subsegmental bronchi and arteries in the right upper lobe of the human lung with special reference to their concomitant relations and double subsegmental arterial supply.

The basic, concomitant topographical relation between the segmental bronchus and artery shows derived figures in the dorsolateral part of the cranial portion of the mammalian lung, especially in humans. However, the pulmonary arterial supply has not been investigated well in the subsegmental level, even in humans. One or two subsegments of S2 received a double arterial supply from both the superior and inferior pulmonary trunks in 39.8% of the right upper lobes of 194 human lung dissections, whereas 20.6% did so in S3, although the latter cases were limited to one of the two subsegments. Moreover, we found several arterial patterns that were significantly frequently observed in a specific group of the bronchial tree in S2 and/or S3. Invasion of an additional artery of inferior trunk origin seemed to happen at the same time in both segments even without complementary territorial relations with the essential segmental artery of the superior trunk origin. S2 and S3 in the human right lung seemed to be the best fields for reconsideration of the basic rules in the lung segment system in mammals as a result of their having the largest sets of variations. We speculate that the discrepancy between the bronchial and arterial ramification patterns, which was frequently found in S2 and S3, is a result of a hypothetical secondary increase of the comparative volume of this area in evolution and/or development of the lung.