Mechanical processing begins with the chewing and mastication by the teeth and tongue. It is continued all along the digestive tract by the involuntary muscle contractions of the smooth muscle lining the stomach walls and intestines. Chemical digestion is the breakdown of food into small organic fragments suitable for absorption by the digestive epithelium. It starts in the mouth where saliva containing certain enzymes begin to break down carbohydrates and continues in the stomach and intestines as other enzymes and acid is released as the food progresses through the digestive tract. Absorption takes place mainly in the small intestines, though important nutrients and water are absorbed by the large intestine.
Compaction is the job of the large intestines.
This makes the feces ready for elimination. Salivary Glands - Secretion of lubricating fluid containing enzymes that breakdown carbohydrates. Endocrine cells secrete hormones. There, the break down of major food molecules takes place, lubrication of the food pathway is provided, and control of the acidity of the food released into the small intestines by the stomach is controlled.