Her given name AE3803 or Red blood cell to say it better is well...a red blood cell. She delivers oxygen to the body and makes sure it gets everything shipped and checked and little known fact about her in the show is that she is a sickle red blood cell which is why she gets lost around the body. She is great friends with White T-Cell U-1146. So are you part of the body or are you a parasite?

AE3803: sigh I'm lost again...um...excuse me can you tell me where the...lungs are...