Spleen/spliːn/ Definition 1 of 3Pro Tip 1/3Localization of Spleen The spleen is located under the ribcage, on your body's left side. My left side hurts; could it be the spleen? Pro Tip 2/3Spleen Functions Besides fighting infection, the spleen filters old blood cells and stores blood. He has trouble fighting infections due to a spleen disorder. Pro Tip 3/3Spleen in Sports In sports, a spleen injury can be serious and needs medical attention. The footballer was sidelined due to a ruptured spleen.