Colon non tumor
General
Normal anatomy

Author: Hanni Gulwani, M.D. (see Authors page)

Revised: 13 December 2016, last major update September 2014

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Colon anatomy[title]
Cite this page: Normal anatomy. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colonanatomy.html. Accessed October 20th, 2017.
Definition / general
  • 1.0 to 1.5 meters long, from terminal ileum to anal canal
  • Compared to small intestine, has greater diameter, fixed position, epiploic appendages, taeniae coli (discontinuous muscular fibers)

Regions:
  • Cecum, ascending (right sided) colon, transverse colon, descending (left sided) colon, sigmoid colon, rectum

Cecum:
  • In peritoneum, 6 x 9 cm
  • Large blind pouch arising from proximal right colon
  • Blind end directed downward, open end directed upward

Ascending colon:
  • 15-20 cm long
  • Posterior surface is in retroperitoneum, but anterior and lateral surfaces have serosa and are intraperitoneal

Hepatic flexure:
  • Junction of ascending and transverse colon

Transverse colon:
  • Connects ascending colon at hepatic / right colic flexure to the descending colon at the splenic / left colic flexure (Wikipedia)

Splenic flexure:
  • Junction of transverse and descending colon

Descending colon:
  • 10-15 cm long
  • Posterior surface is in retroperitoneum, but anterior and lateral surfaces have serosa and are intraperitoneal

Sigmoid:
  • Descending colon at origin of mesosigmoid
  • From pelvic rim to S3 vertebra

Rectum:
  • 12 cm
  • Sigmoid colon from termination of mesosigmoid
  • Also from opposite sacral promontory to upper border of anal canal
  • Becomes extraperitoneal (within the pelvis) as it passes between crura of peritoneal muscles
  • Has no serosa / peritoneal covering

Pouch of Douglas:
  • Cul-de-sac in women made up of reflection of peritoneum from rectum over pelvic wall

Taenia coli:

Epiploic appendages:
  • Pedunculated fat on lateral colon
  • Lined by mesothelium

Vasculature
  • Superior mesenteric artery supplies cecum to splenic flexure
  • Inferior mesenteric artery supplies remainder of colon to rectum
  • Numerous collaterals connect mesenteric circulation with celiac arterial axis proximally and pudental circulation distally
  • Superior hemorrhoidal branch of inferior mesenteric artery supplies upper rectum; hemorrhoidal branches of internal iliac or internal pudental artery supplies lower rectum
  • Venous drainage is similar; there is an anastomotic capillary bed between the superior and inferior hemorrhoidal veins, providing a connection between the portal and venous systems (Surg Oncol 2006;15:243)
Diagrams / tables

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Regions of colon

Cecum and appendix

Cecum and ileocecal valve

Rectovaginal (RV) pouch


Small and large intestine

Iliac, sigmoid or pelvic colon and rectum

Female pelvis

Vascular supply of colon

Clinical images

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Epiploic appendages
(see tip of pointer)

Microscopic (histologic) images

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Taenia coli and lymphoid tissue

Taenia coli: transverse section

Taenia coli: relationship to muscularis propria