Sea Urchin Digestive System
The digestive system of a sea urchin starts at the mouth and unlike humans, the mouth is at the bottom of the body and the anus on the top. The teeth of the Urchin scrape algae and kelp off rocks (their "prey") and after the food is in the mouth, it goes into the esophagus leading to one of the two parts of the stomach. The food first goes into the cardiac stomach, then into the pyloric stomach, and finally out the anus.