Just about all vertebrates have an organ called the "spleen". The spleen has a similar structure to a large lymph node and acts primarily as a blood filter. The spleen plays important roles in regard to red blood cells and the immune system. The spleen removes old blood cells and holds a reserve of blood, which can be valuable in the case of shock. The spleen also synthesizes antibodies in its white pulp and removes antibody-coated bacteria and antibody-coated blood cells by way of blood and lymph node circulation.
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| Image courtesy US Government |
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| Spleen captured under the microscope at 40x magnification. |
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| Spleen captured under the microscope at 100x magnification. |
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| Spleen captured under the microscope at 400x magnification. |
