The main advantage of having an intact digestive tract is that the organs in this system work together to ensure thorough absorption of nutrients from food. WebMD describes the process of digestion as the process of turning food into energy.
According to WebMD, digestion begins with the mouth secreting saliva in response to the smell of food. This saliva, along with the mechanical action of chewing, begins the process of breaking down food into an easily digested form that can be passed through the esophagus to the stomach.
In the stomach, food is bathed in acidic secretions and powerful enzymes that reduce it to a uniform paste. This partially digested food then passes to the small intestine. Secretions from the pancreas and liver continue the work of liquefying the food as it passes through toward the lower GI tract, as described by WebMD.
After as many nutrients as possible have been extracted in the small intestine, the remaining undigested matter is passed to the large intestine where excess water is removed prior to elimination. The end of food's journey is at the rectum, where special sphincters open to permit feces, the final waste product of digestion, to pass easily out of the body, according to WebMD.