Anatomy of the Colon and Rectum

(Click to enlarge picture.) The Digestive System: You can see the transverse colon, sigmoid, and rectum, all of which make up the large intestine.

Food passes through your body along the digestive tract, which includes your esophagus, stomach, small intestine, colon, and rectum. All along this tract, food is broken down, and the nutrients and water are absorbed into the body. What’s left is waste material, also called the stool.

The last part of the digestive tract is the colon and rectum, which together are called the large intestine, or large bowel. Large refers to the diameter of the colon, which is a tubelike organ that goes from the small intestine to your anus. The large colon is between 5 and 6 feet long.     

The section where the digested food first enters it after passing through the small intestine is called the ascending colon. It goes up the right side of your abdomen. The stool passes across the top of your abdomen through the section called the transverse colon and then down the right side through the descending colon.

As the stool passes through, the colon continues to absorb what nutrients and water remain. The section right before the rectum is called the sigmoid colon. The part called the rectum is actually the last few inches of your colon. It’s here that the stool finally collects before it passes out of your body through the anus when you have a bowel movement.

Click to enlarge: Close-up of the large intestine

There are several layers of tissue that make up the walls of the colon. The options you have to treat colon cancer depend partly on what layer the cancer is growing in.