The spleen is a non-vital organ in the body, by which I mean that a person can survive without it. It is not a useless part of the body, as the appendix is, but we are quite capable of living without it.
The spleen is found tucked up behind the stomach on left hand side of our body, just below the diaphragm. It is relatively small organ, about 5x3x2 inches, about the same size as the patient's fist usually. The spleen is made of lymphoid tissue and has very rich blood supply. This reflects its role in the body as a storage area for some blood cells and the removal site of old red blood cells, viruses and other debris.
The spleen on dissection is divided into two types of tissue, red and white pulp. The red pulp is responsible for filtration of blood to remove old blood cells, and also as a storage area for platelets. In some mammals the spleen stores red blood cells, for example horses, but this is not the case in humans. On removal from the circulation the old blood cells are broken down and the components transported to other parts of the body for elimination or reuse.
The white pulp is responsible for aiding the immune system. It has a store of B and T lymphocytes.
Red blood cells are made by the spleen in the womb, but after five months of gestation this function is continued by the bone marrow. The spleen retains its ability to make blood cells, but largely does not in healthy adults.
The spleen may become enlarged in some people (splenomegaly). This may be due to a simple viral infection, reflecting the increased work of the spleen, but should always be investigated, as it may also be a marker of more serious diseases. These include leukemia, sarcoidosis, pernicious anemia and sickle cell anemia.
Other people have a non-functioning or absent spleen,(asplenia), this is common in sickle cell anemia, and is caused by blockage of the blood vessels by sickle cells. More commonly asplenia or an absent spleen is a deliberate move by a surgeon. The rich blood supply to the spleen means that in cases of traumatic injury internal blood loss from this organ can be massive, and the only solution may be removal. The spleen is more likely to be damaged when it is swollen due to a viral infection.
Removal of the spleen does not cause serious consequences normally. The patient will be more susceptible to infections, but other parts of the body do take over production of the B and T lymphocytes needed.
The spleen is not vital to our survival, but the absence of a functioning spleen means other parts of the body have to work harder to fulfill the same functions.