The spleen is an organ that serves quite a few roles in normal bodily function. It has roles in both immune system and hematologic system (the blood) regulation but is not essential for the body's survival. People can be asplenic (lack spleen function) due to surgical removal for a variety of reasons, like trauma, or from disease states (such as sickle cell anemia).
Phagocytosis of Blood Cells and Matter
Phagocytosis refers to the process by which certain cells (known as phagocytes) can engulf and digest bacteria and particles in the blood. It is one of the main mechanisms by which the body protects itself from infection. The spleen acts as a filter for the blood and traps red blood cells within its internal architecture. This way it removes "old" and defective blood cells. Any bacteria or cellular debris that gets filtered in the spleen also get digested by the phagocytes, bolstering bodily immune function.
Production of Antibodies
There are certain localized regions of the spleen that are known as "white pulp" and "red pulp" named due to their characteristic appearances. Immune cells in the body interact at these regions and as a result, cells known as plasma cells are generated primarily in the red pulp region. These cells are the primary producers of antibodies, which are used to fight infectious disease. In some disease states, these antibodies can also target the body's own cells and cause autoimmune disease.
Blood Cell Production
The production of blood cells is known as hematopoiesis. Normally this process ceases in the spleen before birth, but in states of decreased red blood cell production (anemia), the spleen can reactivate and start producing red blood cells. Also in disorders where blood cell production is substantially increased, such as leukemia, the spleen can be one of the sites of cell production.
Sequestration
The spleen serves as a site that filters and sequestrates many elements of the blood, including red blood cells and platelet cells (which assist in the blood clotting process). While normally the spleen at any given time does not sequestrate enough cells to make a difference, in disease states where the spleen enlarges (splenomegaly), it can sequestrate significantly more elements, with the body having less of that respective cell as a result (decreased red blood cells or platelets). The spleen can even end up sequestrating some of the body's white blood cells (which serve immune functions), and that can lead to compromised immunity.
References
- "Robbins and Cotran Pathologic Basis of Disease, Professional Edition, 8th Edition;" Kumar; 2009
- "Hematology: Basic Principles and Practice, 5th Edition;" Hoffman; 2008
