sigmoid colon
The sigmoid colon (or pelvic colon) is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus ' ...
and up to the ano-rectal junction. In
zoology
Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, an ...
inferior mesenteric artery
In human anatomy, the inferior mesenteric artery, often abbreviated as IMA, is the third main branch of the abdominal aorta and arises at the level of L3, supplying the large intestine from the distal transverse colon to the upper part of the a ...
, and venous drainage is to the
portal venous system
In the circulatory system of animals, a portal venous system occurs when a capillary bed pools into another capillary bed through veins, without first going through the heart. Both capillary beds and the blood vessels that connect them are con ...
File:Gray985.png, Abdominal part of digestive tube and its attachment to the primitive or common mesentery. Human embryo of six weeks.
File:Gray1115.png, Tail end of human embryo twenty-five to twenty-nine days old.
File:Illacme plenipes female with 170 segments and 662 legs (SPC000931) - ZooKeys-241-077-g006.jpeg, Metenteron in the milliped '' Illacme plenipes''.