The human digestive system begins with a mouth and
ends with an anus, and is often described as a "tube within a tube." Variously
called the gut, alimentary canal, or the gastrointestinal tract, the digestive
system extends from the lower part of the head region through the entire torso.
Essentially, this system carries out five separate jobs that have to do with the
processing and distribution of nutrients. First, it governs ingestion or food
intake. Second, it transports food to organs for temporary storage. Third, it
controls the mechanical breakdown of food and its chemical digestion. A fourth
function is the absorption of nutrient molecules. Its final piece of work is the
temporary storage and then elimination of waste products.
