Stephen J. Schueler, M.D.

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Irritable Bowel Syndrome Anatomy

To better understand irritable bowel disease, it helps to understand the anatomy of the gastrointestinal tract.

Gastrointestinal Anatomy
The esophagus is a muscular tube that propels food down to the stomach. The stomach is the most dilated portion of the digestive tube, situated between the esophagus and the beginning of the small intestine (duodenum). It lies in the upper central portion of the abdomen (above the umbilicus) and to the left of the midline. The stomach produces gastric juice (acidic), which serves to breakdown proteins.

The intestine is a long, continuous, tube inside the body. It lets the body absorb nutrients from food and liquids. The intestine is about 22 feet long. It includes the large intestine (colon) and the small intestine.

The small intestine has three parts:

  • Duodenum:
    • Connects to the stomach
  • Jejunum:
    • Middle portion of the small intestine
  • Ileum:
    • Lower portion of the small intestine that connects to the cecum (first part of the large intestine)

The large intestine is also known as the colon. It is the last portion of the intestine.

The colon has several parts, including:
  • Cecum:
    • The portion of the colon that connects to the ileum (small intestine). The appendix is a finger-like pouch that comes off of the cecum.
  • 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

Gastrointestinal anatomy:
  • Esophagus and stomach
  • Intestines
  • Blood vessels of the intestines
  • Entire gastrointestinal tract

Last Updated: Dec 16, 2010 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Irritable Bowel Syndrome References
  1. El-Serag HB, Pilgrim P, Schoenfeld P. Systemic review: Natural history of irritable bowel syndrome. Aliment Pharmacol Ther. 2004 Apr 15;19(8):861-70. [15080847]
  2. Hungin AP, Chang L, Locke GR, Dennis EH, Barghout V. Irritable bowel syndrome in the United States: prevalence, symptom patterns and impact. Aliment Pharmacol Ther. 2005 Jun 1;21(11):1365-75. [15932367]
  3. Payne S. Sex, gender, and irritable bowel syndrome: making the connections. Gend Med. 2004 Aug;1(1):18-28. [16115580]
  4. Spanier JA, Howden CW, Jones MP. A systematic review of alternative therapies in the irritable bowel syndrome. Arch Intern Med. 2003 Feb 10;163(3):265-74. [12578506]
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