ABSTRACT
The rectum begins where the tinea coli of the sigmoid colon join to form a continuous outer longitudinal muscle layer at the level of the sacral promontory. The rectum follows the curve of the sacrum and ends at the anorectal junction. The embryological hindgut forms the upper rectum, while the lower rectum is derived from the cloaca and is surrounded by extraperitoneal connective tissue. The superior rectal artery is the direct continuation of the inferior mesenteric artery and is the main arterial supply of the rectum. The superior haemorrhoidal veins draining the upper half of the anal canal above the dentate line pass upwards to become the rectal veins; these unite to form the superior rectal vein, which later becomes the inferior mesenteric vein. This forms part of the portal venous system and ultimately drains into the splenic vein.
