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Sigmoid colon: anatomy, location and function

The sigmoid colon is the S-shaped last part of the colon. It runs from the end of the descending colon at the pelvic brim to the rectum. It reabsorbs water, vitamins and minerals, firming the stool before it reaches the rectum.

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Highlighted in the model: Sigmoid colon. Click any part to read about it, or switch off “Highlight topic” to see the whole body. Use Male / Female to switch bodies. 3D data: BodyParts3D, © The Database Center for Life Science; knee ligaments, menisci, tonsils, palate and parotid glands from the Human Reference Atlas Visible Human Male model and female parts from its Visible Human Female model (HuBMAP / NIH); lung lobes built from the BodyParts3D chest; all CC BY 4.0; meshes simplified and recoloured. The default body is an adult male.

Sigmoid colon at a glance

What it is
The sigmoid colon is the S-shaped last part of the colon. It runs from the end of the descending colon at the pelvic brim to the rectum.
Location
It begins in front of the pelvic brim as the descending colon curves medially into the pelvis, and becomes the rectum at about the level of the third sacral vertebra (S3), where it loses its mesentery. Behind it lie the left internal iliac vessels, the left ureter, piriformis and the sacrum.
Function
It reabsorbs water, vitamins and minerals, firming the stool before it reaches the rectum.
Body system
Digestive · single, midline structure
FMA ID
FMA14548 (Foundational Model of Anatomy)

Key facts

  • Its length varies a lot: StatPearls gives 25 to 40 cm on average, TeachMeAnatomy about 40 cm and Radiopaedia about 15 cm.
  • It hangs on an inverted V-shaped mesentery, the sigmoid mesocolon, which makes it very mobile.
  • Two to four sigmoid arteries from the inferior mesenteric artery supply it.

Clinical relevance

Diverticulitis is common here, and a long sigmoid colon can twist around its mesocolon (sigmoid volvulus), cutting off its blood supply.

Structures next to the sigmoid colon

The nearest named structures in the 3D model, measured from the centre of each part:

References

  1. Foundational Model of Anatomy: Sigmoid colon (FMA14548). EMBL-EBI Ontology Lookup Service.
  2. Harkins J.M., Sajjad H. Anatomy, Abdomen and Pelvis, Sigmoid Colon. StatPearls (NCBI Bookshelf NBK549824), updated 2023.
  3. Radiopaedia. Sigmoid colon.
  4. TeachMeAnatomy. The Large Intestine.
  5. OpenStax. Anatomy and Physiology 2e, §23.1 Overview of the Digestive System. Rice University, 2022.
  6. Mitsuhashi N. et al. (2009). BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Research 37, D782–D785. Data © The Database Center for Life Science, CC BY 4.0.

Related anatomy

Explore the whole body in the interactive 3D human anatomy model, or browse the A–Z list of human structures.