Spleen - body's largest lymphatic organ, located directly below the diaphragm and behind the 9th, 10th, and 11th ribs. Spleen's function is to destroy old or defective red blood cells, and produce white blood cells. Spleen can be damaged from a direct blow to the ribs above it. Kehr's sign is one indicator of injury to the spleen. Kehr's sign is referred pain to the upper left quadrant and left shoulder.
Mononucleosis causes an inflamed spleen.
Persons with mono should be withheld from competition until inflammation decreases. If spleen is injured and removed, the liver takes over its functions. Liver - Liver is the largest organ in the body. The liver is the reservoir for blood in the body. Also helps in filtering out poisons out of the blood.