Colitis (Types)

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)
    Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)

    Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)

    Dr. Anand received MBBS degree from Medical College Amritsar, University of Punjab. He completed his Internal Medicine residency at the Postgraduate Institute of medical Education and Research, Chandigarh, India. He was trained in the field of Gastroenterology and obtained the DPhil degree. Dr. Anand is board-certified in Internal Medicine and Gastroenterology.

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Colitis and the anatomy of the colon

The colon, or large intestine, is a hollow, muscular tube that processes waste products of digestion from the small intestine, removes water, and ultimately eliminates the remnants as feces (stool) through the anus. The colon is located within the peritoneum, the sac that contains the intestine, located in the abdominal cavity.

The colon is surrounded by many layers of tissue. The innermost layer of the colon is the mucosa that comes into contact with the waste products of digestion. The mucosa absorbs water and electrolytes back into the blood vessels that are located just below the surface in the submucosa. This is surrounded by a circular layer of muscles and then another outer layer of longitudinal muscles that run along the length of the colon. The muscles work together to rhythmically squeeze liquid waste from the cecum through the entire length of the colon. Water is gradually removed, turning the waste into formed stool, so that it is excreted out of the anus in solid form.

The colon frames the organs within the peritoneum, and its segments are named based on their location.

  • The colon usually begins in the right lower quadrant of the abdomen, where the terminal ileum, the last part of the small intestine, attaches to the cecum, the first segment of the colon. The appendix is attached to the cecum.
  • The ascending colon begins at the cecum and arises from the right lower abdomen to the right upper abdomen near the liver.
  • The colon then makes a sharp left turn called the hepatic flexure (hepatic=liver), and is referred to as the transverse colon, as it makes its way to the left upper quadrant of the abdomen near the spleen.
  • There is a sharp downward turn called the splenic flexure, and it is referred to as the descending colon as it runs from the left upper quadrant to the left lower quadrant of the abdomen.
  • When it descends into the pelvis, it is referred to as the sigmoid colon.
  • The last several centimeters of the colon are referred to as the rectum.
  • The anus is the final portion of the colon. Continue Reading
Reviewed on 2/26/2016
References
REFERENCES:

Crohn's and Colitis Foundation of America. "Living with Crohn’s & Colitis."
<http://www.ccfa.org/living-with-crohns-colitis/>

Kasper, D., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Professional, 2015.

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