Human spleen. Coloured Computed Tomography (CT) scan of an axial section through the abdomen, showing the spleen, stomach and liver. At lower centre is a vertebral bone of the spine (white); rib bones (white) surround the internal organs. The spleen (pink) is seen behind the stomach (green); the abdomen at this level is occupied largely by the liver (orange). The spleen is part of the lymphatic system, involved in processing white blood cells (lymphocytes). It also regulates the number of red blood cells in the bloodstream by destroying old cells. CT scanning is a diagnos- tic technique which uses X-rays to produce cross- sectional slices" through the body."