As food moves through the digestive tract, secretions are added to lubricate, liquefy, buffer, and digest the food. Mucus, secreted along the entire digestive tract, lubricates the food and the lining of the tract. The mucus coats and protects the epithelial cells of the digestive tract from mechanical abrasion, stomach acid, and digestive enzymes. The secretions also contain large amounts of water, which liquefies the food, making it easier to digest and absorb. Water also moves into the intestine by osmosis. Liver secretions break large lipid droplets into much smaller droplets, which makes the digestion and absorption of lipids possible. Enzymes secreted by the oral cavity, stomach, small intestine, and pancreas break down large food molecules into smaller molecules that can be absorbed by the intestinal wall.