GI System

Gastro-Intestinal System (GI System)

The digestive system (gastrointestinal tract) is the set of organs (mouth, pharynx, esophagus, stomach, small intestine and large intestine) responsible for digestion, i.e. the transformation of food so that it can be absorbed and used by the body’s cells.

Its function is the transportation (food), secretion (digestive juices), absorption (nutrients) and excretion (through the process of defecation).


The digestion process is the same in all monogastric animals, transforming carbohydrates, lipids and proteins into simpler units thanks to digestive enzymes. Then they can be absorbed and transported by the blood.


Description and functions

The digestive tract is a long tube with important associated glands. It is in charge of transforming food into simple substances that the organism can easily use.


From the mouth to the anus, the digestive tract is about eleven meters long. Digestion begins in the mouth. The teeth grind the food, and the secretions of the salivary glands moisten it and initiate its chemical decomposition.


Then, the food bolus crosses the pharynx, continues through the esophagus and reaches the stomach, a muscular bag of one and a half liter capacity, under normal conditions, whose mucosa secretes the potent gastric juice. In the stomach, the food is agitated until it becomes the chyme.


At the stomach’s exit, the digestive tract is prolonged by the small intestine, which is about six meters long, although it is significantly retracted on itself.


In its first portion or duodenum, it receives secretions from the intestinal glands, bile and pancreatic juices. All these secretions contain many enzymes that degrade food and transform it into simple soluble substances.


The digestive tract continues through the large intestine for a little more than a meter and a half in length. Its final portion is the rectum and the anus; here, the indigestible food remains are evacuated to the outside.