Bowel Facts

The digestive system consists of a tubular structure designed for the digestion and absorption of food as well as the expulsion of unusable ingested materials. This system also has accessory structures that play roles in other systems of the body as well as the digestive system.

The bowel: what it is, what it does
The bowel, also known as the colon or large intestine, is the lower portion of the digestive system. This is the internal plumbing that takes the part of our food that can’t be used in the body and makes it ready for disposal. The food we eat begins its journey at the mouth, and proceeds through the throat and esophagus to the stomach.

Major digestive action starts in the stomach, and is continued in the small or upper intestine. The food, which is moved through the digestive system by a propulsive action, has become mainly waste and water by the time it reaches the bowel, a five-foot-long tube.

By the time the stool reaches the final section of the bowel, called the sigmoid colon, it has lost much of the water that was present in the upper part of the digestive system. The stool finally reaches the rectum, and—on command from the brain—is consciously eliminated from the body with a bowel movement through the anal canal.

Normal bowel functioning can range from three bowel movements a day to three a week. Despite the widely recommended “one movement a day,” physicians agree that such frequency is not necessary. The medical definition of “infrequent” bowel movements is “less often than once every three days.” Most physicians agree that a movement less often than once a week is not adequate.

The rectum, the last 4–6 inches of the digestive tract, signals when a bowel movement is needed. It remains empty until just before a bowel movement. The filling of the rectum sends messages to the brain via nerves in the rectal wall that a bowel movement is needed.

From the rectum, the stool passes into the anal canal, guarded by ring-shaped internal and external sphincter muscles. Just prior to being eliminated, the stool is admitted to the anal canal by the internal sphincter muscle, which opens automatically when the rectal wall is stretched by a mass of stool. The external sphincter, on the other hand, is opened by a conscious decision of the brain, so that bowel movements can be performed only at appropriate times.

Digestive System At A Glance

Things to Know:

• When you eat, your body digests the food so your cells can use it to make energy. Food passes through the mouth, esophagus, stomach, small intestine, large intestine, rectum, and out the anus.

• The digestive system breaks down food two ways:
  • mechanical digestion- the chewing (in the mouth) and churning (in the stomach)
  • chemical digestion- with the help of enzymes, into substances that cells can absorb and use. This occurs in the mouth, stomach and small intestines.

• Once food gets partially broken down in the stomach, it becomes a thin watery liquid called chyme.

• The pancreas releases digestive enzymes into the small intestines. The small intestine is where food is broken down into molecules tiny enough for the body cells to use. In the villi are tiny tubes that carry blood called VESSELS. Food molecules are taken into these blood vessels. Once the food is in the blood, it can travel all over the body.

• The large intestines absorb excess water from chyme so it can be used by the body.