Did you even know you had a spleen? The spleen is a large organ next to your stomach. The spleen doesn’t belong to the digestive system, it is part of the blood stream. Scientist have discovered some of what the spleen does but have not yet found all its functions. The spleen makes new red blood cells (especially in children) and creates some white blood cells (disease fighters). The spleens most important function is destroying blood cells. Inside your body there is constantly new blood cells being created and old cells being destroyed. The spleen is responsible for breaking down the old blood cells. The spleen is important to the body but if it is diseased can be removed. The liver takes over the spleens functions if necessary.