The two tissue types in the spleen determine its functions. These tissue types are the red pulp (splenic pulp) and the white pulp (splenic lymphoid nodules). The red pulp is made out of blood and reticular fibres. The red pulp determines what is good for the blood. It filters the blood, recycling iron and clearing unwanted substances. The unwanted substances are usually old and deteriorated red blood cells. The white pulp consists of small nodules that contain an abundance of lymphocytes which the body uses to fight infection and stay healthy. About half of the body’s monocytes are stored in the spleen. These white blood cells protect and promote the healing of damaged tissue.
Though the liver can adequately take over the functions of the spleen, without a spleen, humans are disposed to infections as there will be a significant absence of lymphocytes. It’s absence also diminishes response to certain vaccines. The spleen also contains extra platelets in storage for use during emergencies such as extreme injuries. When you are injured, the spleen releases the platelets that are the essential ingredient for blood to clot and protect the body.
For the first five months in the womb, the fetus uses the spleen as a secondary site of red blood cell production. However, after that, all human red blood cells are produced in the bone marrow only, and the spleen only filters them. Some metabolic products such as properdin, opsonins and tuftsin are also produced in the spleen and help support the immune system.