The spleen, a spongy, soft organ about as big as a person’s fist, is located in the upper left part of the abdomen, just under the rib cage. The splenic artery brings blood to the spleen from the heart. Blood leaves the spleen through the splenic vein, which drains into a larger vein (the portal vein) that carries the blood to the liver. The spleen has a covering of fibrous tissue (the splenic capsule) that supports its blood vessels and lymphatic vessels.
The spleen is made up of two basic types of tissue, each with different functions:
White pulp
Red pulp
The white pulp is part of the infection-fighting system (immune system Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more ). It produces white blood cells called lymphocytes Lymphocytes One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more 
, which in turn produce antibodies Antibodies One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more (specialized proteins that protect against invasion by foreign substances).
The red pulp filters the blood, removing unwanted material. The red pulp contains other white blood cells called phagocytes Innate Immunity One of the body's lines of defense (immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more that ingest microorganisms, such as bacteria, fungi, and viruses. It also monitors red blood cells, destroying those that are abnormal or too old or damaged to function properly. In addition, the red pulp serves as a reservoir for different elements of the blood, especially white blood cells White Blood Cells The main components of blood include Plasma Red blood cells White blood cells Platelets read more 
and platelets Platelets The main components of blood include Plasma Red blood cells White blood cells Platelets read more (cell-like particles involved in clotting). However, releasing these elements is a minor function of the red pulp.
Viewing the Spleen
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Asplenia
People can live without a spleen (a condition called asplenia).
Asplenia is loss of splenic function due to
Absence of the spleen at birth
A disease that affects the function of the spleen (functional asplenia)
Surgical removal of the spleen (splenectomy)
Absence of the spleen at birth is a rare disorder. Infants with this disorder often also have a heart defect Overview of Heart Defects About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more .
People with functional asplenia have a spleen that does not function properly. Functional asplenia can be due to a variety of diseases. Common causes include sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more 
, celiac disease Celiac Disease Celiac disease is a hereditary intolerance to gluten (a protein found in wheat, barley, and rye) that causes characteristic changes in the lining of the small intestine, resulting in malabsorption... read more 
, and alcohol-related liver disease Alcohol-Related Liver Disease Alcohol-related liver disease is liver damage caused by drinking too much alcohol for a long time. In general, the amount of alcohol consumed (how much, how often, and for how long) determines... read more 
. Functional asplenia can also occur after injury to the arteries or veins of the spleen.
Splenectomy is surgical removal of the spleen. It can be done in otherwise healthy people after a spleen injury Spleen Injury Because of the spleen’s position in the upper left side of the abdomen, a severe blow to the stomach area can damage the spleen, tearing its covering, the tissue inside, or both. An injured... read more (such as after a motor vehicle accident) or in people with diseases that cause the spleen to enlarge Enlarged Spleen An enlarged spleen is not a disease in itself but the result of an underlying disorder. Many disorders can make the spleen enlarge. Many disorders, including infections, anemias, and cancers... read more .
When the spleen is removed or does not function, the body loses some of its ability to produce protective antibodies and to remove unwanted microorganisms from the blood. As a result, the body’s ability to fight infections is impaired. However, other organs (primarily the liver) compensate for the loss by increasing their infection-fighting ability and by monitoring for and removing red blood cells that are abnormal, too old, or damaged.
People who do not have a spleen are at particularly high risk of infections because of the spleen’s role in fighting certain kinds of bacteria, such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Because of this risk, people receive vaccinations Overview of Immunization Immunization (vaccination) helps the body defend itself against diseases caused by certain bacteria or viruses. Immunity (the ability of the body to defend itself against diseases caused by... read more to help protect them from infection with these organisms. People should also be sure they receive the influenza vaccine Influenza Vaccine The influenza virus vaccine helps protect against influenza. Two types of influenza virus, type A and type B, regularly cause seasonal epidemics of influenza in the United States. There are... read more every year and the COVID-19 vaccine COVID-19 Vaccine Coronavirus disease 2019 (COVID-19) vaccines provide protection against COVID-19. COVID-19 is the disease caused by infection with the SARS-CoV-2 virus. There are multiple COVID-19 vaccines... read more . Some people take daily antibiotics to prevent infections, particularly when they have another disorder (such as sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more or cancer) that increases the risk of developing infections or have regular contact with children.
