| Sigmoid colon | |
|---|---|
 Drawing ofcolon seen from front (sigmoid colon coloured blue) | |
 | |
| Details | |
| Precursor | Hindgut |
| Part of | Large intestine |
| System | Digestive system |
| Artery | Sigmoid branches ofinferior mesenteric artery,sigmoid arteries,internal iliac artery |
| Nerve | Inferior mesenteric ganglia andsacral nerve[1] |
| Identifiers | |
| Latin | colon sigmoideum |
| MeSH | D012809 |
| TA98 | A05.7.03.007 |
| TA2 | 2987 |
| FMA | 14548 |
| Anatomical terminology | |
 |
| Major parts of the |
| Gastrointestinal tract |
|---|
Thesigmoid colon (orpelvic colon) is the part of thelarge intestine that is closest to therectum andanus. It forms a loop that averages about 35–40 centimetres (14–16 in) in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thussigma +-oid). This part of thecolon normally lies within thepelvis, but due to its freedom of movement it is liable to be displaced into theabdominal cavity.[2]
The sigmoid colon begins at thesuperior aperture of thelesser pelvis, where it is continuous with theiliac colon, and passes transversely across the front of thesacrum to the right side of the pelvis.
It then curves on itself and turns toward the left to reach the middle line at the level of the third piece of thesacrum, where it bends downward and ends in therectum.
Its function is to expel solid and gaseous waste from the gastrointestinal tract. The curving path it takes toward the anus allows it to store gas in the superior arched portion, enabling the colon to expel gas without excreting faeces simultaneously.
The sigmoid colon is completely surrounded byperitoneum (and thus is notretroperitoneal), which forms amesentery (sigmoid mesocolon), which diminishes in length from the center toward the ends of the loop, where it disappears, so that the loop is fixed at its junctions with theiliac colon and rectum, but enjoys a considerable range of movement in its central portion.
Pelvic splanchnic nerves are the primary source forparasympathetic innervation.Lumbar splanchnic nerves providesympathetic innervation via theinferior mesenteric ganglion.
Behind the sigmoid colon are theexternal iliac vessels, ovary, obturator nerve, the leftpiriformis, and leftsacral plexus of nerves.
In front, it is separated from thebladder in themale, and theuterus in thefemale, by some coils of thesmall intestine.
![[icon]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aWiki_letter_w_cropped.svg) | This sectionneeds expansion. You can help byadding missing information.(February 2014) |
Diverticulosis often occurs in the sigmoid colon in association with increased intraluminal pressure and focal weakness in the colonic wall. It is a common cause ofhematochezia.
Volvulus occurs when a portion of the bowel twists around its mesentery, which can lead to obstruction andinfarction. Volvulus in the elderly commonly occurs in the sigmoid colon, whereas in infants and children it is more likely to occur in the midgut. This may correct itself spontaneously or the rotation may continue until the blood supply of the gut is cut off completely.
This article incorporates text in thepublic domain frompage 1182 of the 20th edition ofGray's Anatomy(1918)
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