Arterial segmentation and subsegmentation in the human spleen.

The segmental nature of the arterial tree of the human spleen was analyzed in 181 subjects of both sexes, who had died of various accidental causes. Based on the observation of the pattern of the terminal and polar splenic branches, selective arteriographs and corrosion casts, and taking account of the ideas reported in the literature, we proposed that the spleen is divided in arterial segments and subsegments. Segments are the territories corresponding to both the primary branches of the splenic artery (primary segments) and the polar arteries (polar segments). In 92.82% of the cases there are two primary segments and in 7.18% three primary segments. Associated to these, in 29.28% there is a superior polar segment, in 44.75% an inferior polar segment, and in 10.49% both superior and inferior polar segments are present. Thus, the number of segments varies from two to five. Occasionally, two or three inferior polar segments can be present. Subsegments are the territories corresponding to the extrasplenic subdivisions of the primary branches and the polar arteries. According to the number of arterial subdivisions, the subsegments can be of second, third, fourth, fifth or sixth order. The last branches of the splenic artery (penetrating arteries) are all subsegmentary in nature and supply hilar or polar subsegments. Anastomoses between extrasplenic branches of the splenic artery were observed in 19.89% of the cases. Sometimes, thin anastomotic bridges could be observed between arterial splenic compartments.