The small intestine is the major site for digestion and absorption of nutrients. The small intestine is up to 6 meters long and is 2-3 centimeters wide. The upper part, the duodenum, is the most active in digestion. Secretions from the liver and pancreas are used for digestion in the duodenum.
To start the process of fat digestion, the base of the tongue secretes an enzyme called lingual lipase. Saliva and other fluids blend with food to form lumen.
