The spleen is located under the left side of the diaphragm, and has a smooth, convex surface that faces the diaphragm. The spleen is an organ that plays a very important role in the red blood cells and the immune system. The spleen metabolizes hemoglobin from senescent erythrocytes. The globin part of hemoglobin is broken down into its constituent amino acids, and the heme part is metabolized into bilirubin, which is eliminated by the liver.

The splenic system stores and purifies erythrocytes, metabolizes hemoglobin and recycles iron. The spleen also provides an essential function for the immune system by mounting a primary immune response to antigens in the blood and synthesizing antibodies. Endothelial cells, fibroblasts and splenocytes are essential components required for the normal functioning of the spleen cell system.