Leeches
Like all other Annelids, leeches are have a hydroskeleton are coelemate, and have external segmentation of their bodies. The body surface of the animal can be divided into 102 outer circular rings, whereas its internal structures are divided into 32 segments. The first four anterior segments are designated as head segments, which include a brain and sucker. This is followed by 21 midbody segments, including two reproductive organs, and 9 pairs of testes. Finally, the last seven segments are fused to form the animal's tail sucker, as well as its posterior brain. Leeches are used for medical uses such as trauma doctors at Johns Hopkins, the University of Maryland and other U.S. hospitals routinely use leeches as a temporary measure to keep blood flowing as new vessels grow in a damaged area