The human spleen is an organ found in humans with important roles in regard to red blood cells and the immune system.
It is located in the left upper quadrant of the abdomen.
The spleen is part of your lymphatic system, which fights infection and keeps your body fluids in balance. It contains white blood cells that fight germs. The human spleen also helps control the amount of blood in human body, and destroys old and damaged cells.
The spleen is encased in a thick connective-tissue capsule. Inside, the mass of splenic tissue is of two types, the red pulp and the white pulp, which do not separate into regions but intermingle and are distributed throughout the spleen. The white pulp is lymphoid tissue that usually surrounds splenic blood vessels. The red pulp is a network of channels (sinuses) filled with blood, and it is in the red pulp that most of the filtration occurs.