Sigmoid colon

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Sigmoid colon
Front of abdomen, showing surface markings for liver, stomach, and great intestine.
Latin	colon sigmoideum
Gray's	subject #249 1182
Artery	sigmoid arteries
Nerve	superior mesenteric ganglia, sacral nerve [1]
Precursor	hindgut
Dorlands/Elsevier	c_47/12249909

The sigmoid colon (pelvic colon; sigmoid flexure) forms a loop which averages about 40 cm. in length, and normally lies within the pelvis, but on account of its freedom of movement it is liable to be displaced into the abdominal cavity.

Contents 1 Path 2 Coverings 3 Innervation 4 Relations 5 Additional images 6 References 7 External links

[edit] Path

It begins at the superior aperture of the lesser pelvis, where it is continuous with the iliac colon, and passes transversely across the front of the sacrum 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 the sacrum, where it bends downward and ends in the rectum. According to Isaac Asimov's book The Human Body, the name sigmoid means "S-shaped."

[edit] Coverings

It is completely surrounded by peritoneum (and thus is NOT Retroperitoneal), which forms a mesentery (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 the iliac colon and rectum, but enjoys a considerable range of movement in its central portion.

[edit] Innervation

Pelvic splanchnic nerves are the primary source for parasympathetic innervation.

[edit] Relations

Behind the sigmoid colon are the external iliac vessels, the left Piriformis, and left sacral plexus of nerves.

In front, it is separated from the bladder in the male, and the uterus in the female, by some coils of the small intestine.

[edit] Additional images

Intestines

Sigmoid colon and rectum, showing distribution of branches of inferior mesenteric artery and their anastomoses.

Iliac colon, sigmoid or pelvic colon, and rectum seen from the front, after removal of pubic bones and bladder.

Sagittal section of the lower part of a female trunk, right segment.

[edit] References

1. ^ Physiology at MCG 6/6ch2/s6ch2_30

[edit] External links

• Sigmoid+colon at eMedicine Dictionary
• SUNY Figs 37:06-07 - "The large intestine."
• Norman/Georgetown sup&infmesentericart

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

v • d • e Anatomy of torso, digestive system: Gastrointestinal tract Upper GI: to stomach Mouth • Pharynx (nasopharynx, oropharynx, hypopharynx) • Esophagus • Crop Upper GI: stomach rugae – gastric pits – cardia/gland – fundus/gland – pylorus/gland – pyloric antrum – pyloric canal – greater curvature – lesser curvature – angular incisure Lower GI: intestines Small intestine: Duodenum (Suspensory muscle, Major duodenal papilla, Minor duodenal papilla) • Duodenojejunal flexure • Jejunum • Ileum • continuous (intestinal villus, crypts of Lieberkühn, circular folds) Junction: Vermiform appendix • Ileocecal valve Large intestine: Cecum • Colon (ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon) • continuous (taenia coli, haustra, epiploic appendix) Lower GI: termination Rectum: Houston valve • rectal ampulla • pectinate line Anal canal: anal valves • anal sinuses • anal columns • Hilton's white line Anus: Sphincter ani internus muscle • Sphincter ani externus muscle Lower GI: lymph GALT: Peyer's patches (M cells)