1. The Digestive System Prepares food for use by all body cells.

7. Hydra heir bodies are basically just a hollow cylinder, which is solid at the base, with an opening at the mouth end. The mouth leads into the hollow interior of the cylinder which acts as the digestive cavity. The mouth is surrounded by a variable number of tentacles (usually somewhere between 6 and 10). Because the digestive cavity has only one opening, food and subsequently, digested waste, both come in and go out through the same opening.

8. Earthworm A earthworm has a digestive system. It eats dirt, digesting the plant and animal matter in the dirt and then eliminates the rest. It has an esophagus for the food to go down, a crop to store the food in, a gizzard that grinds the food down, intestines for the food to pass through and take out nutrients and an anus for the food to come out.

17. Anatomy of the Mouth and Throat

18. Human Deciduous and Permanent Teeth

22. Peristalsis

24. Stomach

26. Movements in Stomach

33. Large Intestine

39. The Excretory System Gets rid of wastes and other substances that the body doesn’t need.

46. Urinary System