Answer
The three main functions of the digestive system are to process/digest food, extract nutrients, and eliminate indigestible residues .
Work Step by Step
The digestive system carries out its main functions in five stages:
1. Ingestion--the taking in of food substances
2. Digestion--the mechanical and chemical breakdown of food
3. Absorption--the uptake of nutrients through epithelial cells and thence to blood and lymph.
4. Compaction; this is the absorption of water, and the consolidation of indigestible residues
5. Defecation--the elimination of indigestible residues/feces.
