Sigmoid colon

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The sigmoid colon ( the pelvic colon ) is part of the large intestine closest to the rectum and anus. It forms a loop that averages about 35-40 cm in length. This loop is usually shaped like the Greek letter sigma (?) Or the Latin S (thus sigma -oid ). This part of the large intestine is usually located inside the pelvis, but because of its freedom of movement, it can be transferred into the abdominal cavity.

Video Sigmoid colon

Structure

The sigmoid colon starts in the superior aperture of the lower pelvis, where it continues with the iliac colon, and passes across the front of the sacrum to the right side of the pelvis. (The sigmoid name correctly means S-shaped.)

Then it curves to itself and turns to the left to reach the center line at the third cut level of the sacrum, where it bends down and ends in the rectum.

Its function is to dissipate solid waste and gas from the digestive tract. The required arcing path to the anus allows it to store gas in the superior curved part, allowing the colon to release the gas without throwing away the feces simultaneously.

Closing

It is completely surrounded by peritoneum (and thus not retroperitoneal), which forms a mesentery (sigmoid mesocolon), which decreases from the center to the end of the loop, where it disappears, so the loop remains at its junction. with the iliac colon and rectum, but has a fairly large range of motion in the middle.

Supply of nerves

Pelvic splanchnic nerve is the main source for parasympathetic innervation. Lumbar splanchnic nerves provide sympathetic innervation through the inferior mesenteric ganglion.

Relationships

Behind the sigmoid colon are external iliac vessels, ovaries, obturator nerves, left piriformis, and left sacral nerve plexus.

Up front, it is separated from the bladder in men, and the uterus in women, by some small intestine scrolls.

Maps Sigmoid colon

Clinical interests

Diverticulosis often occurs in the sigmoid colon in association with increased intraluminal pressure and focal weakness in the colonic wall. This is a common cause of hematochezia.

Volvulus occurs when part of the intestine is wrapped around a mesentery, which can cause obstruction and infarction. Volvulus in the elderly usually occurs in the sigmoid colon, whereas in infants and children it is more likely to occur in midgut. This may repair itself spontaneously or rotation may continue until intestinal blood supply is completely cut.

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Additional images

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References

This article combines text in the public domain of page 1182 of the 20th edition of Gray's Anatomy (1918)

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External links

• Anatomical figure: 37: 06-07 in Human Anatomy Online, SUNY Downstate Medical Center - "Colon."
• Excellent & amp; Inferior Mesenteric Artery in Anatomy Lesson by Wesley Norman (Georgetown University)

Source of the article : Wikipedia