Digestion of starch starts from mouth. Salivary Glands secrete an enzyme called ptyalin (salivary amylase), which converts starch and glycogen of cooked food into limit dextrins, maltose and isomaltose.
In stomach, mainly digestion of protein takes place. Gastric glands produce gastric juice which contains proenzyme-Prorennin and pepsinogen. Rennin (in calf) converts casein (milk protein) into calcium paracaseinate for curdling it. Pepsin converts calcium paracaseinate into peptons. Another enzyme called gastric lipase active in infants changes milk fat tributyrin into fatty acids and glycerol. Oesophagus conveys food to stomach through peristalsis.
Duodenum is a part of small intestine, which secretes intestinal juice (succus entericus). This juice contains enzymes for carbohydrate, fat, protein, nucleic acid digestion.