The superior mesenteric artery is crossed anteriorly by the splenic vein and the neck of the pancreas. Posterior to the artery are the left renal vein, the uncinate process of the pancreas, and the inferior part of the duodenum. After giving off its first branch (the inferior pancreaticoduodenal artery), the superior mesenteric artery gives off jejunal and ileal arteries on its left (Fig. 4.126). Branching from the right side of the main trunk of the superior mesenteric artery are three vessels—the middle colic, right colic, and ileocolic arteries—which supply the terminal ileum, cecum, ascending colon, and two-thirds of the transverse colon.