It’s one organ, but it consists of two distinct tissue types that perform two distinct functions. Red pulp helps to filter the blood, removing unwanted elements. White pulp is full of lymphocytes that help the body fight infection. Filtering blood and fighting infection are essential jobs; what is this important organ? The spleen.

Unless you injure your spleen, chances are you don’t give it much thought. This soft organ, made up of spongy material, is located on the left side of the abdomen, tucked just under the rib cage. It is about the size of the heart and can hold up to three gallons of blood.

The spleen performs a number of important jobs. As we noted above, it serves as a filter, removing old blood cells, breaking them down, disposing of waste and returning needed iron to the blood. It also helps fight infection by bringing blood in contact with its lymphocytes, which attach to viral, bacterial or parasitic invaders and direct antibodies against them.

The spleen doesn’t stop there. Because it is capable of holding up to three gallons of blood, the spleen acts as a reservoir, in case of emergencies. With a person experiences sudden blood loss, the body signals the spleen to contract. When this happens, blood is expelled from the spleen and returned into circulation.

The spleen also stores platelets, which help to clot blood. When the body is injured and bleeding, the spleen disburses platelets to the site of the injury.

Finally, the spleen manufactures red blood cells in a human fetus. After birth, red blood cells are manufactured solely in the bone marrow, but in cases of bone marrow breakdown, the spleen has the ability to begin manufacturing red blood cells again.

The spleen can be injured or affected by disease. In case of injury – car accident, fall or other trauma to the abdominal area – the spleen can rupture. Severe blood loss can result.

Symptoms of an injured spleen include abdominal pain, tenderness in the upper left abdomen, left shoulder pain, signs of shock and blood loss. An injury to the spleen can be life threatening. Seek medical attention if you believe your spleen has been injured.

Because of its soft, spongelike texture, the spleen cannot usually be repaired surgically and is removed to stop the blood loss. When the spleen is removed, the liver and lymphatic system are able to take over the functions of the spleen. This results in increased risk of infection, however, because the spleen and the lymphocytes it contained are no longer present to help the body fight against infection.

A number of diseases affect the spleen, including bacterial, parasite and viral infections as well as liver disease, tuberculosis, leukemia, malaria, rheumatoid arthritis, lupus, sickle cell anemia, mononucleosis, fungal infections and certain blood diseases. When the spleen is affected by a disease, it becomes enlarged. This is a condition known as splenomegaly.

Problems with the spleen can be difficult to diagnose. It may be difficult to tell exactly where the pain originates and symptoms may be attributed to other conditions, such as problems with the stomach and digestive system, heart attack or angina. Blood tests can help to pinpoint a diagnosis.

Although we don’t often spend mornings around the water cooler discussing the marvels of the spleen, this soft, spongelike organ that rests behind our ribcage performs numerous important functions, including filtering the blood and fighting infection. In case of injury or disease, the body can function without a spleen, but its ability to fight infection is compromised when the spleen is removed.