Splenic v mesenteric
Blood in the mesenteric vein comes in from the ascending colon.
Blood in the splenic vein comes in from the descending colon via the inferior mesenteric vein and the spleen. The splenic vein and the superior mesenteric vein combine to form the hepatic portal vein going into the liver. Blood mixes from the ascending and descending colons as it enters the portal vein.