What Does the Spleen Do? A Simple Explanation.

The spleen is a small but major organ of the lymphatic system, an important part of the immune system that protects the body against infection. The spleen is located directly under the rib cage on the left side of the abdomen.

It consists of two main types of tissue - red pulp and white pulp.

Red pulp or 'splenic pulp', is made up of blood and fibers. It helps to filter the blood, removing old, damaged or malformed red blood cells, and harmful microorganisms.

White pulp, which is also known as 'splenic lymphoid nodules' or 'Malpighian bodies of the spleen', is made up of small nodules that help create antibodies to fight infections in the body.

In humans, the spleen acts as a reserve for extra platelets, which help the blood to clot, in case they are needed. It also stores about half of the body's monocytes, which are white blood cells that protect and promote the healing of damaged tissue. In some animals (not humans) the spleen stores extra red blood cells in case of emergency.

Before birth, the spleen of a fetus produces red blood cells. However, once a baby is born, the bone marrow entirely takes over production of these cells.

A further function of the spleen is to produce various substances to support the immune system, such as opsonins, properdin, and tuftsin.

Once a human is born, he or she can live without a spleen. If it does have to be surgically removed for any reason, the liver will take over the function of the spleen. However, studies show that the person could be more prone to infections once the spleen is removed.

Ancient Greek, Roman and Islamic people believed that the human body was filled with four basic fluids, which they called the "four humors". They believed that these humors had to be balanced correctly in the body to maintain good health. One of these humors was 'Black Bile', or 'melancholy', which was believed to be controlled by the spleen. Too much melancholy was thought to cause despondency, sleeplessness and irritability.

This belief was adopted by European physicians. 16th century English playwright and poet William Shakespeare often referred to the spleen in his plays, believing that laughter kept the spleen healthy, and that an unhealthy spleen was unable to contain and control the black bile that theoretically caused depression.

The theory was not discarded until the nineteenth century.

Traditional Chinese physicians believe that the condition of the spleen affects willpower and temperament.