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What Is the Colon?

The Anatomy, Functions and Health of Your Colon

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Updated January 05, 2012

The human colon is a vital part of your personal plumbing system. This tubular organ works around the clock to remove waste products from your body. As part of the digestive system, the colon works alongside organs like the stomach and small intestine to remove stool and maintain your fluid and electrolyte balance.

Can You Live Without a Colon?

Although it is an amazing organ, it is possible to live without a colon. People have portions of their colon removed in surgery everyday -- surgical bowel resection is one of the treatment options for colon cancer. However, all six feet of your colon, also called the large intestine, serve a purpose. The majority of the nutrients you eat are absorbed in the small intestine well before the "food" reaches your colon. The colon’s primary job is to form the one and a half quarts of fluid (the food you ingested mixed with digestive juices) into firm stool for passage out of the body.

The colon must reabsorb water and electrolytes to form stool. This is why, when you are dehydrated, you can get constipated and your stool may become hard and difficult to pass. The colon is pulling more fluid from the stool for your body to use.

Anatomy of the Colon

The colon is not labeled very creatively – most of the labels for the colon correspond to their anatomical location and flow of stool. Your large intestine is broken down into six sections including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon and the rectum. The colon begins at the end of the small intestine, where it is called the cecum, and ends at the rectum. Cancers of the large intestine are casually referred to as colon, rectal, or colorectal cancer.

The cecum is anatomically located in the lower right sight of your abdomen approximately where your appendix is attached. The cecum is the widest part of your entire colon and is approximately 5 centimeters long, or a third as long as a pen. Between 15 and 20 percent of all colon cancers occur in the cecum.

The ascending colon heads up vertically from the cecum to the transverse colon. The juncture between the cecum and transverse colon is called the right colic flexure, or the hepatic flexure for its proximity to your liver (hepatic system). Anatomically, the ascending colon is about 10 centimeters long and is seated in the right side of your abdomen.

The transverse colon connects your ascending and descending colon, traveling lengthwise across your abdomen. The transverse colon lies close to your stomach, liver and gallbladder and is approximately 50 centimeters long.

The descending colon begins at the left colic flexure, also known as the splenic flexure for its proximity to the spleen. This portion of your colon lies in the left side of your abdomen, connecting your transverse colon to your sigmoid colon. The descending colon is approximately 10 centimeters long.

Roughly 25 percent of colon cancers originate in the ascending, transverse or descending colon.

The sigmoid colon makes up the last 50 centimeters of colon leading to the rectum and typically has an 'S' curve or shape to it. Roughly 20 to 25 percent of all colon cancers originate in the sigmoid colon, which is anatomically situated just above your pelvis.

The rectum is the final portion of your large intestine leading to the anus. The digestive process has completely finished by the time stool reaches the rectum, where it waits to be passed as a bowel movement. About 25 to 30 percent of cancers originate in this 15-centimeter piece of the large intestine.

Quick Look at a Colon Section

The colon is composed of four layers, each with a specific function. When a diagnosis of colon cancer is made, the pathologist will determine what layer the cancer has reached (such as innermost or outermost layer) to help determine the staging of your cancer. The majority of colorectal cancers will start in the innermost layer, called the mucosa, and spread toward the outermost layer, or the serosa, of the colon over time if untreated. Starting at the innermost layer of the colon, the layers include the:

  • Mucosa – Divided into three subtissues, the mucosa surface is called the epithelium, where most colon and rectal cancers originate. The mucosa provides a lubricant, which helps aid in the passage of stool through the colon.

  • Submucosa – The next layer of your colon, which is rich in blood vessels and nerves. The submucosa is a connective tissue layer connecting the mucosa to the next muscle layer.

  • Muscularis Propria – The third layer is composed of opposing layers of muscle fibers -- a set that runs horizontally and a set that runs around the colon. Once cancers reach through this layer, there is an increased chance that they can metastasize to other parts of the body.

  • Serosa – The outermost layer of your colon. When cancer spreads through the serosa it has left the colon and metastasized.

Keep Your Colon Happy

Your colon is a simple organ with simple needs. Keep it hydrated, clean, and get routine screening exams to check the inner lining for polyps or growths that can precede cancer. Diets high in fat, sugar and excessive red meat consumption (more than 18 ounces a week) may increase your risk for colon cancer. Smoking, obesity and excessive alcohol consumption may also adversely affect your colon’s health.

Help your colon function at its best by:

  • Eating a high-fiber diet rich in whole grains, fruits and vegetables
  • Limiting red meat and processed meat (hot dogs) consumption
  • Drinking plenty of fresh water daily
  • Get daily exercise
  • Stop using tobacco products including cigarettes and snuff
  • Limit your alcohol intake
  • Talk to your doctor about a daily multivitamin if your diet is poor
  • Learn more about screening exams to monitor your colon’s health

It’s never too late to start learning about your colon and taking a proactive stand toward keeping it healthy. Early detection of colon cancer saves lives – learning more about your colon and keeping it healthy could save yours.

Sources:

American Cancer Society. (2006). American Cancer Society’s Complete Guide to Colorectal Cancer. Clifton Fields, NE: American Cancer Society.

Witmer, L. (2007, January 23). Clinical anatomy of the large intestine. Accessed: January 2, 2012.

Harvard School of Public Health. (n.d.). Protein: What Should I Eat? Accessed: January 1, 2012.

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