Stephen J. Schueler, M.D.

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Hemorrhoids Anatomy

To better understand hemorrhoids, it helps to understand the anatomy of the colon, rectum, and anus.

The large intestine is also known as the colon. It is the last portion of the intestine. The colon has several parts, including:

  • Ascending colon: the first section after the small intestine, located on the right side
  • Transverse colon: sits horizontally across the upper abdomen
  • Descending colon: located on the left side of the abdomen
  • Sigmoid: a short, S-shaped section above the rectum
  • Rectum: the lowest internal part of the colon

Intestinal anatomy:
  • Entire gastrointestinal tract
  • Intestines and other abdominal organs
  • Blood vessels of the intestines

The anus is the opening on the gastrointestinal tract, where the stool exits. The anus marks the transition from the lining of the gastrointestinal tract to the external skin. The anal canal is a tube, 1-2 inches long that leads to the anus. The anal canal is surrounded by circular muscles, called sphincters, and blood vessels. The sphincters control defecation.

Last Updated: Nov 3, 2008 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Hemorrhoids References
  1. Gearhart SL. Symptomatic hemorrhoids. Adv Surg. 2004;38:167-82. [15515618]
  2. Iyer VS, Shrier I, Gordon PH. Long-term outcome of rubber band ligation for symptomatic primary and recurrent internal hemorrhoids. Dis Colon Rectum. 2004 Aug;47(8):1364-70. [15484351]
  3. MacKay D. Hemorrhoids and varicose veins: a review of treatment options. Altern Med Rev. 2001 Apr;6(2):126-40. [11302778]
  4. Ortiz H, Marzo J, Armendariz P, De Miguel M. Stapled hemorrhoidopexy vs. diathermy excision for fourth-degree hemorrhoids: a randomized, clinical trial and review of the literature. Dis Colon Rectum. 2005 Apr;48(4):809-15. [15785901]
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