Digestive System
The gastrointestinal tract (mouth, esophagus, stomach, small intestine, large intestine) plus accessory organs (liver, gallbladder, pancreas) that break food down and absorb nutrients.
Mechanical digestion (chewing, stomach churning) increases surface area while chemical digestion (enzymes, stomach acid, bile) breaks bonds. Carbohydrate digestion starts in the mouth with salivary amylase, protein digestion starts in the acidic stomach with pepsin, and bile from the liver emulsifies fats in the small intestine.