The Digestive Process: The Large Intestine

The large intestine is one of the many important parts of your digestive tract. This is a series of organs that starts with your mouth and ends with your anus, the opening of your rectum.

The food that you eat passes from your mouth through your esophagus to your stomach. It then goes from your stomach to your small intestine. These organs break down food into bits that your body absorbs and uses for energy. By the time the food you eat gets to your large intestine, most of the digestion is done. The large intestine is also called the colon and the large bowel.

The job of your large intestine is to absorb water, minerals, and some of the remaining nutrients from your food. It will change the leftover waste into a bowel movement. This is also called stool. Your rectum stores the stool until you feel the need to have a bowel movement. Muscles of your rectum then push the stool through your anus and out of your body.

Anatomy of your large intestine

Your small intestine connects to your large intestine in the lower right part of your belly (abdomen). Your entire large intestine is about 5 feet long. It's divided into several segments:

• Cecum. Digested food from your small intestine goes into this pouch. Your appendix hangs off the end of your cecum.

• Ascending colon.  This segment extends along the right side of your abdomen. It's about 9 inches long.

• Hepatic flexure. In the upper right part of your abdomen, under your liver, this part of the large intestine makes a turn to the left.

• Transverse colon.  This segment travels across the upper part of your abdomen, from right to left.

• Splenic flexure. In the left upper side of your abdomen, your large intestine is located under your spleen. At this flexure, your large intestine turns downward.

• Descending colon. In the left side of your abdomen, your large intestine descends for about 5 inches.

• Rectosigmoid colon.  This part is about 5 inches long and leads into your rectum.

• Rectum. This part of your large intestine stores stool. It's about 6 to 8 inches long and leads to your anal canal.

The hollow inside of your large intestine is known as the lumen. Its lining is called mucosa. It has special folds and projections to help it absorb nutrients. A layer of muscle (muscularis propria) supports the walls of your large intestine.

The role of bacteria

Most of the bacteria that live in your body—and there are billions of them—live inside your large intestine. These bacteria are important in digestion and in keeping your large intestine healthy. The good bacteria that live in your colon are called your normal flora. They help prevent bad bacteria from multiplying and causing problems.

Bacteria also help break down fiber. This is an important part of your diet that contributes to digestive health by preventing constipation. Normal bacterial flora also secrete vitamin K and vitamin B that you can absorb. The gas that you make is the result of the hard-working normal flora in your colon.

Tips for a healthy large intestine

Problems that can develop with your large intestine include constipation, inflammation, and cancer. The following are some general tips to keep your large intestine working well:

• Begin regular screening for colon cancer at age 45, or when your healthcare provider recommends. This will depend on your family history.

• Maintain a healthy weight.

• Exercise regularly.

• Include lots of fiber, vegetables, fruits, and whole grains in your diet.

• Stay hydrated and drink plenty of water each day.

• Cut back on red meat and processed meats, such as cold cuts, hot dogs, and sausages.

• Don't smoke. Drink alcohol only in moderation.

Warning signs of trouble with your large intestine may include the following:

• A change in bowel habits

• Bloating

• Abdominal (belly) pain

• Constipation

• Diarrhea

• Blood in your stool

Tell your healthcare provider if you have any of these symptoms. The best way to fix problems with your large intestine is to find them as early as possible.