The process of breaking down food into small nutrient molecules is called digestion. Digestion begins in the mouth, where food is chewed and mixed with saliva to form a soft mass called a bolus. The bolus travels down the esophagus and into the stomach, where it is further broken down by stomach acid and enzymes. The stomach then churns the food and sends it to the small intestine where it is further digested by enzymes from the pancreas and bile from the liver. Bile helps to break down fats. The nutrients from the digested food are absorbed through the walls of the small intestine and sent to the liver. Undigested materials move on to the large intestine and are eventually excreted from the body as feces.