In some animals the food is physically broken down as it is ingested.
Some animals have internal, hardened structures utilized for grinding food.
Some animals utilize hard, foreign structures in a specialized section of the digestive system, e.g., the gizzard of birds and earthworms. This occurs in snakes. The food may be living plankton or non-living, organic detritus. The combination of cilia and mucus is often utilized. In other animals, appendages with large numbers of setae are involved.