The Fluke's Cardiovascular system
Flukes are a Platyhelminthes that enters the body and goes into the hosts internal organs and uses them for nutrients. The fluke has no respiratory, cardiovascular, or digestive system, so it feeds off its hosts blood or other internal organs, such as the lung or liver, for all the nutrients it needs. All food that the fluke eats through the mouth is regurgitated out the mouth, which also serves as the anus. These flukes can give many diseases and can sometimes be dangerous, but are very uncommon amongst civilization, and are mostly found in rainforest and jungles.