About the Spleen
The spleen is a soft, oval organ that is about the size of a paperback book and is located in the left upper quadrant of the abdomen. It lies completely beneath the ribs and is surrounded by the stomach, pancreas and kidney.
For many years it was thought that the spleen was an unnecessary organ, like the appendix. Indeed, Hippocrates thought it was the source of black bile and Galen wrote it was "an organ full of mystery." Therefore, the spleen was removed whenever it was injured. In the Middle Ages it was removed as a way to rid the body of evil humors.
Since nothing usually happened when the spleen was removed, the concept that the spleen served no important role was maintained until the 1950s. It was then shown that the spleen was an important organ in preventing serious, overwhelming infection.
What does the spleen do?
The spleen clears the blood of old red blood cells and platelets. Red blood cells carry oxygen in the blood. Platelets are the tiny cells that form the second line of defense against bleeding. When a blood vessel is cut, the blood vessel contracts to stop, or at least diminish, the bleeding. Next, platelets clump at the site of injury to form a plug that temporarily stops the bleeding. Finally, clotting factors in the blood are activated to help the platelets form the clot.
The spleen also produces antibodies that help fight bacterial infections. Most important are the antibodies it produces against polysaccharide encapsulated (sugar coated) bacteria, such as pneumococcus, meningococcus and hemophilus.