Arterial supply to the human rectum.

The arterial supply to the human rectum was studied in 42 autopsy specimens. 32 were fixed in formalin and dissected. Five were radiographed after filling their arterial bed with a radio-opaque substance. The remaining five specimens were used to prepare plastic casts of the arterial bed. The superior rectal artery is the chief rectal artery. It forms a recto-sigmoid branch, an upper rectal branch and then divides into right and left terminal branches. Terminal branches extend downwards and forwards around the lower two thirds of the rectum to the level of the levator ani. The middle rectal artery, of appreciable diameter, on one or both sides of the rectum, is found supplying a limited part of the rectum in 12% of the specimens. Its presence can be anticipated by observing the diameter of the superior rectal artery and its two terminal branches. The inferior rectal artery supplies the anal canal below the levator ani. Rectal twigs of other pelvic arteries terminate at the pararectal tissues occasionally reaching the wall of the rectum. Extramural anastomoses were not observed between the main rectal arteries, but intramural ones were present, mainly between the superior and the inferior rectal arteries.