Indicate the organ system that directly provides the metabolism in the animal body.

The metabolism is provided by the digestive system. It can be different in every kind. In humans, it begins in the mouth, where food is prepared for digestion. Namely – chewing and the beginning of the breakdown of disaccharides. Through the esophagus, food enters the stomach, where it is digested by acids and enzymes. Further, the residues pass through the intestines, where the body finally absorbs useful substances and finally leaves the body. In humans, this process takes about 12 hours.