The spleen is an organ in the lymphatic system. The lymphatic system maintains the body's fluid balance and helps fight against infection.
The spleen, which is about the size of a fist, is located on the left side of the body, under the ribs and above the stomach.
The spleen helps store and release white blood cells, which can regulate inflammation and help heal injured tissue. It also filters blood and helps break down old red blood cells, so they can be recycled into new cells.
Diseases involving the spleen include sickle cell anemia, which causes abnormally shaped red blood cells, and malaria. Injuries can also damage or rupture the spleen, especially if it is swollen.
Although it is possible to survive without a spleen, people without spleens require extra vaccinations and are more likely to contract bacterial infections.
If part of the spleen is removed, the spleen can sometimes regenerate.