A novel branching pattern of the superior mesenteric artery found in the bullfrog (Rana catesbeiana) amphibian

The branching and distribution patterns of the superior mesenteric artery w ere studied in 10 adult bullfrogs (Rana catesbeiana) after injection of col oured latex solution into the vasculature. The abdominal digestive organs i n the bullfrog were mainly supplied by the coeliac artery and the superior mesenteric artery, both of which arose as a common trunk, the coeliacomesen teric artery, from the abdominal aorta. The coeliac artery supplied the sto mach, liver, gallbladder and the pancreas, whereas the first branch of the superior mesenteric artery was the splenic artery with other branches suppl ying the greater part of intestine. The apex of the intestinal loop was def ined as the region supplied by the trunk of the superior mesenteric artery, and its intestinal branches constituted a 'nested formation' which had the following characteristics. (1) The branches of the trunk were distributed to both sides of the apex, and the distribution regions of younger branches were located more distant from the apex than those of older branches. (2) Two branches directed towards both sides of the trunk frequently made a com mon stem arising from the trunk. The second branch of the superior mesenter ic artery constituted a secondary trunk and its distribution region could b e defined as a secondary apex, since 1 of its branches also constituted a n ested formation which was distributed to both sides of the primary and seco ndary apices. The intestinal branches of the superior mesenteric artery wer e divided into 4 types on the basis of their pattern of branching and cours e. It is suggested that the nested formation of the superior mesenteric art ery in the bullfrog is a remnant of the vascular pattern of the tadpole, wh ich possesses a double spiral mode of intestinal convolution, probably supp lied by arteries with the nested formation in a latent form.