The spleen is an important organ in humans that performs three major functions, namely the production and storage of white blood cells for immune defense and the sorting out of obsolete red blood cells.
What is the spleen?
Schematic diagram showing the anatomy of the spleen. Click to enlarge. The spleen is the largest lymphoid organ in humans, that is, the largest organ in the human body where lymphocytes, also called white blood cells, are formed. Thus, it belongs to the lymphatic system, which is another vascular system in the human body along with the blood circulation. The spleen, however, is not separate from the bloodstream, but instead is firmly integrated into it, as it is responsible for the formation and storage of white blood cells as well as the elimination of outdated red blood cells. Since white blood cells are responsible for recognizing foreign bodies in the blood, such as bacteria or viruses, and eliminating them by immunological means, the spleen is an important component of the immune system. However, it is not among the vital organs in adult humans.
Anatomy and structure
The spleen is found in every mammal. In humans, it is located in the left upper abdomen between the left kidney and the diaphragm. It usually weighs between 150 and 200 grams with a length of about 12 cm, a width of about 7 cm, and a thickness of about 4 cm. The spleen is surrounded by a capsule from which sheath walls extend into the interior of the spleen. Together, the capsule and sheath walls form the basic anatomical framework of the spleen, composed of reticular fibers and cells. Due to its dual function, the spleen is divided into two distinct organs: the white and red pulp. Inside the spleen there are several Malpighi bodies. These are lymphoid follicles, also called splenic nodules, which together form the white pulp. The space between the nodules is supplied with blood and represents the red pulp.
Functions and tasks
The spleen is part of the lymphatic system and serves as a filter. It is referred to as a bipartite organ consisting of white and red pulp, as the two hold different functions. While one part of the spleen is responsible for the formation of lymphocytes, the white blood cells, the other part breaks down the old erythrocytes, the red blood cells. The white pulp is responsible for the formation of white blood cells. Since white blood cells are responsible for immune defense, the spleen contributes a great deal to a healthy immune system. The breakdown of old red blood cells is handled by the red pulp, which can also store white blood cells and platelets and release them when needed. Just as the spleen is capable of breaking down damaged blood cells, it is also capable of eliminating other components, including antibody-laden cells, immune complexes or firbin homomers, but also microorganisms that could harm the body. Even though the function of the spleen is impressive, it is not a vital organ for adults – but it is for children up to the age of six, because during this period the spleen is significantly involved not only in the formation of white blood cells, but also red blood cells.
Diseases
The spleen is an organ with which there are rarely problems due to disease. It becomes dangerous when the spleen ruptures, for example when the ribs are injured. In technical jargon, this is called a splenic rupture. If such a splenic rupture occurs, there is a risk that the spleen will bleed into the abdominal cavity. This can be life-threatening for the affected person, which is why the spleen is often surgically removed in such a case. This is usually not a problem for adults, as they can live well without a spleen. However, since the spleen makes a significant contribution to the immune defense system, there is an increased risk of affected individuals contracting bacterial infections more frequently after the spleen has been removed. Other diseases of the spleen include inflammation of the spleen, splenic infarction or so-called amyloidosis. In order to be able to carry out examinations of the spleen, an ultrasound is usually performed, and now and then also a computer tomography. The spleen cannot usually be palpated unless it is enlarged due to disease.Splenic enlargement can have various causes and may indicate splenic tumors and splenic metastases, result from leukemia, or occur after malaria infection or viral disease.
Typical and common diseases
- Splenomegaly
- Splenitis
- Splenic infarction
- OPSI syndrome