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Large Intestine
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Large Intestine

Key Features
The arge intestine begins at the ileocecal valve and ends at the anus; it frames the small intestine, with which it is continuous.
Compared to the small intestine, it is shorter in length, but larger in diameter.
Taeniae coli
    • Three longitudinal ribbon-like bands of muscle fibers that travel the length of the large intestine. The taeniae coli represent the muscularis tunic of the large intestine.
    • They act like an elastic band that pulls on the large intestine and causes it to bunch and form haustra.
  • Haustra
    • Pouch-like structures.
  • Epiploic appendages (aka, omental appendages)
    • Small fat-filled sacs, attach to the tenaie coli.
Key Functions
  • Receives undigested materials from the small intestine.
  • Absorbs water and ions from the undigested materials, which converts the remaining materials to feces (the small intestine is the primary place of nutrient absorption).
  • Stores and expels feces.
Subdivisions of the large intestine
  • Cecum (appendix attaches, here)
  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid colon
  • Rectum
  • Anal canal, which opens to external environment via the anus.
    • External and internal anal sphincters regulate passage of feces.
    • External anal sphincter comprises voluntary skeletal muscle
    • Internal anal sphincter comprises involuntary smooth muscle
Key Landmarks:
  • Right colic flexure (aka, hepatic flexure)
Indicates where the ascending becomes the transverse colon inferior to the liver.
  • Left colic flexure (aka, splenic flexure)
Indicates where the transverse colon becomes the descending colon inferior to the spleen.
  • Distal sigmoid colon and rectum lie within the pelvis.
  • Anal canal lies within the perineum, external to the abdominopelvic cavity.
Clinical Correlations
In diverticulosis, outpockets form within the mucosa of the large intestine become inflammed with or without infection (diverticulitis).
Diverticulosis
Inflammatory bowel disease (IBD) refers to chronic inflammation of the GI tract Ulcerative colitis causes continuous ulcers, specifically within the lining of the large intestine.
Inflammatory Bowel Disease, ulcerative colitis
Crohn's disease is characterized by inflammation that spreads deep into the walls of the GI tract.
Crohn's Disease
CT Scans
large intestine ct
large intestine transverse ct scan
For more, see our Abdominal CT Scan Atlas on the Course Page

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