A 62-year-old man has had 4 months of worsening constipation with cramping pain that comes in waves and eases after a few minutes; he cannot point to one spot when asked where it hurts. His abdomen is distended and tympanitic, with mild tenderness in the left iliac fossa and no guarding. Colonoscopy shows a fixed narrowing of the descending colon through which the scope will not pass.
Which one of the following pairs - the site at which his colicky pain is felt and the artery supplying the narrowed segment - would you expect in this man?