[Vascular anatomy of the anorectal transition]

Based on selective dye injection studies, the regions of supply of the 3 rectal arteries have been defined. The cranial portion of the rectum receives its blood supply from the superior rectal artery, the inferior rectal artery supplies the entire rectal wall in a fan-shaped configuration up to the dentate line. A wedge-shaped portion of the muscularis in the proximal distribution of the inferior rectal artery receives a relatively reduced supply. The middle rectal artery can supply a variable portion of the muscularis which is usually supplied by the distal superior rectal artery. Intramural anastomoses between these regions exist only between the superior and inferior rectal arteries at the level of the dentate line in the submucosa.