Vascularization of the rectum
The rectum is used to store stool (continence) and for controlled excretion (defecation). The arterial supply of the rectum is provided by three arteries. The upper rectal artery (Arteria rectalis superior), which originates from the lower intestinal artery (Arteria mesenterica superior), supplies the upper part of the rectum.
The middle rectal artery (Arteria rectalis media), which originates from the internal iliac artery (Arteria iliaca interna), supplies the middle part of the rectum. The lower part of the rectum is supplied arterially by the lower rectal artery (Arteria rectalis inferior), which originates from the internal pudendal artery (Arteria pudendalis interna). Venous outflow is via the inferior and middle rectal veins (Venae rectales mediae et inferiores) into the inferior vena cava.
The superior rectal vein (Vena rectalis superior) is used for venous outflow of the upper part of the rectum. In contrast to the other two rectal veins, this vein does not run into the inferior vena cava, but via the inferior mesenteric vein into the portal vein system (vena portae) of the liver (vascular supply to the intestine).
