The role of the digestive system is to process the food that you eat into forms that can be absorbed and used throughout the various tissues of the body for healthy functioning.
Food is broken down in the digestive tract - the long, twisting canal that includes the mouth, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus. The outer walls of the digestive tract have layers of muscle and tissue that move food along its path through waves of contraction. The inner lining of the digestive tract has glands that secrete the acids and enzymes needed to break food down into usable nutrients. Undigested matter is eliminated from the anus as waste.
The liver and pancreas produce digestive juices that enter the intestine through small ducts. The gallbladder helps by storing juices produced by the liver until they are ready for use in the intestine. The nervous system and the circulatory systems also play major roles in the digestive system.
How Food Moves Through the System
Digestion begins in the mouth where food is chewed and reduced to a finer texture. Saliva moistens it and begins to process it chemically. When food is swallowed it is pushed into the esophagus, which allows it to pass through to the stomach.
The stomach has three tasks:
Store swallowed food and liquid
Mix up the contents with digestive enzymes and juices
Empty mixed contents slowly into the small intestine
The Small Intestine
Different types of food take varying amounts of time to pass into the small intestine from the stomach. Carbohydrates pass more quickly, while proteins take longer and fats take the longest.
Digestive enzymes from the pancreas and bile from the liver work with intestinal juices to break food down further and the contents in the intestines are pushed along its path. Digested food can then be absorbed through the intestinal wall into the circulatory and lymphatic systems for distribution throughout the body.
Undigested materials are pushed into the colon, where most of the water is absorbed and the solid material is expelled through the anus by a bowel movement.
The Colon and IBS
The colon connects the small intestine to the rectum and anus. Its major function is to absorb water and nutrients from the partially digested food that enters from the small intestine.
Nerves, hormones, and muscle contractions control the movement of contents in the colon towards the rectum. If these processes do not work properly, the contents inside the colon move too fast or too slowly, resulting in abdominal pain, cramps, constipation or diarrhea
When contents move too quickly, the colon loses its ability to absorb fluids. The result is too much fluid in the stool. If movement is too slow, too much fluid is absorbed causing constipation.
In people with IBS, the colon may respond strongly to certain foods or to stress, causing problems that might not occur in other people.
