How does a healthy digestive system work?

Your digestive system is vital to your health. It processes the food you take in, absorbing the nutrients and energy your body needs and eliminating the waste that you don't need. Under normal circumstances, food travels from your mouth, down the esophagus to the stomach, and through the small intestine, where essential nutrients are absorbed. Then, whatever is not used moves to the colon, also known as the large intestine or bowel. This is the stage of the process that is most directly related to your regularity.

As the solid food waste passes through it, your colon gradually soaks up the remaining water in the waste and shapes it into stool. In the colon, gentle wavelike muscle contractions known as peristalsis slowly push stool downward toward the rectum, and stronger contractions then signal the urge to have a bowel movement.

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The "gut." It's an ancient Anglo-Saxon word that refers to the human digestive system. Think of this marvel of nature's engineering as a perpetual food processor, constantly mixing, grinding, and transforming the meats, vegetables, fruits, and snacks that people eat into biologically useful molecules.

Nearly 30 feet long if stretched out straight, the gut is a series of hollow organs linked to form a long, twisting tube that runs from the mouth to the anus. This string of organs is known as the alimentary canal, gastrointestinal (GI) tract, or digestive tract. It comprises the esophagus (or gullet), stomach, small intestine, and colon (which includes the rectum). These organs break down food and liquids -- carbohydrates, fats, and proteins -- into chemical components that the body can absorb as nutrients and use for energy or to build or repair cells. What's left is expelled by a highly efficient disposal system.

The organs of the gut are almost always moving, driven by muscles in their walls. These muscles consist of an outer longitudinal layer and an inner circular layer. The coordinated contractions of these layers push food and fluids the length of the canal, just as rolling waves deposit sand and shells on the shore. This dynamic movement along the gastrointestinal tract is known as peristalsis.

Helping with the job of digestion is the mucosa, or lining, of the mouth, stomach, and small intestine, which harbors glands that produce digestive enzymes. The salivary glands, liver, and pancreas also secrete juices that help make food soluble (dissolvable in water) so that nutrients can pass easily into the bloodstream.