The colon, also referred to as the large intestine is the final section of the gastrointestinal (GI) tract. Its primary function is to extract water, salts and other substances from food content passing through the body’s digestive system. Most nutritional absorption occurs in the small intestine, the part of the gastrointestinal tract positioned above the colon. However, in the colon, absorption of fluids, sodium and fat-soluble vitamins forms solid fecal matter that can be expelled from the body. The colon walls are coated in special bacteria that help with this process.
The first part of the colon, also known as the cecum, begins in the lower right-hand side of the abdomen. The remainder of the colon has four distinct sections, which listed from “top” to “bottom” of the large intestine are:
Colon cancer can occur anywhere within the large intestine; however, is more likely to emerge lower down the gastrointestinal tract (the left colon). That being said, cancers involving the right side of the colon can only be detected early by means of colonoscopy examination or CT colonography (or virtual colonoscopy) and would be missed by sigmoidoscopy exam. The rectum and anus have lower rates of cancer than the remainder of the colon. If you have questions about colon anatomy or health, please contact a colonoscopy specialist.
Reviewed 12/14/2011 by David M. Nolan, M.D.
Diplomate of the American Board of Internal Medicine, 2011
Currently a Fellow of Gastroenterology, at UCI 2011-2014