Spleen

The spleen is a small part of you.

It is inside your belly on the left side. It is purple in color.

This organ acts like a filter. It cleans your blood by removing old cells. It also keeps a small reserve of blood. This can help if you lose blood.

The spleen helps you stay well. It works with your body to fight germs. It has two main parts that do different jobs.

One part helps fight sickness. The other part cleans the blood. It is a very busy helper!

The spleen is a purple organ in your body.

You can find it in the upper left part of your belly. It sits under your ribs.

The spleen acts like a filter for your blood. It has two main parts called pulp.

One part is called red pulp. This part cleans the blood. It uses special cells to find and remove old red blood cells. It also stores a reserve of blood. This can help if you lose blood during an injury. The red pulp also keeps cells that help heal injured tissue.

The other part is called white pulp. This part helps your immune system. The immune system is how your body fights germs. The white pulp holds cells that find tiny germs in the blood. These cells make antibodies. Antibodies are tools that help fight sickness.

In humans, the spleen can hold up to 240 ml of blood. It also stores many white blood cells. This helps keep you safe from infections.

The spleen is a vital organ found in almost all vertebrates. In humans, it is a purple organ located in the upper left part of the abdomen. It sits underneath the ninth, tenth, and eleventh ribs.

This organ acts as a large filter for your blood. It also plays a major role in your immune system. Without it, you might be more likely to get certain infections.

The spleen works using two different types of tissue called pulp. The first part is the red pulp, which surrounds the white pulp. The red pulp acts like a mechanical filter for your blood. It uses cells called macrophages to find and remove old or damaged red blood cells.

This part also stores monocytes, which are cells that can travel to help heal injured tissue. It can even hold a reserve of up to 240 ml of blood for emergencies.

The second part is the white pulp, which helps with your immune response. The white pulp contains special areas called follicles and lymphoid sheaths. These areas hold B lymphocytes and T lymphocytes, which are types of white blood cells.

When these cells encounter germs in the blood, they can activate. They then create antibodies, like IgM and IgG, to fight the invaders. This process is a key part of your adaptive immune system.

Scientists have studied the spleen for a long time to understand its many jobs. While the source does not name a single discoverer, we know it is a central part of the mononuclear phagocyte system. In humans, the spleen is unique because it develops from mesenchymal tissue. This is different from most other organs in the gut.

During fetal life, the spleen even helps produce all types of blood cells. This job usually stops after the fifth month of pregnancy.

You can think of the spleen as a combination of a cleaning station and a security guard. The red pulp cleans the blood by removing old cells, just like a filter in a pool. The white pulp acts like a security guard, looking for germs and calling for help.

If a person has to have their spleen removed through surgery, it is called a splenectomy. People without a spleen must be extra careful about certain bacteria. This is because the spleen is the largest collection of lymphoid tissue in the body.

The spleen is a vital organ found in almost all vertebrates. In humans, it is a purple organ located in the left upper quadrant of the abdomen. It sits underneath the ninth, tenth, and eleventh ribs.

This organ acts primarily as a blood filter and a major part of the immune system. It is the largest collection of lymphoid tissue in the human body. The spleen plays critical roles in managing red blood cells and protecting against infection.

The spleen functions through two distinct types of tissue: red pulp and white pulp.

The red pulp surrounds the white pulp and the marginal zone. It consists of venous sinuses and splenic cords known as the cords of Billroth. As blood travels through the red pulp, it undergoes mechanical filtration. Specialized cells called macrophages actively remove old, damaged, or antibody-coated red blood cells and pathogens. The red pulp also serves as a storage site for monocytes. These cells can be mobilized to sites of tissue injury, such as the heart after a myocardial infarction, where they differentiate into dendritic cells and macrophages to promote healing.

The white pulp manages the body's adaptive and innate immune responses.

It contains specific structures called Malpighian corpuscles, which are made of nodules. These include lymphoid follicles rich in B lymphocytes and periarteriolar lymphoid sheaths (PALS) rich in T lymphocytes. The PALS are situated around central arterioles. This specific positioning allows B lymphocytes to encounter antigens carried in the blood. Once activated, B cells differentiate into plasma cells. These plasma cells then secrete antibodies, such as IgM and later IgG, to fight invaders.

In humans, the spleen has a unique developmental history. While most organs in the gut are derived from endoderm, the spleen comes from mesenchymal tissue. It forms within and from the dorsal mesentery. Despite this different origin, it shares the celiac trunk blood supply with other foregut organs. During fetal life, the spleen is a hematopoietic organ, meaning it produces all types of blood cells. This function typically ceases after the fifth month of gestation. In adults, the bone marrow becomes the primary site for blood cell production, though the spleen can still produce lymphocytes.

The physical dimensions of the spleen vary based on several factors. In healthy adults, its length correlates with height, body weight, and the degree of acute congestion. It does not correlate with age or sex.

For example, a woman who is 180–184 cm tall may have a spleen length between 9.3 and 13.4 cm. A man of the same height may have a length between 8.6 and 13.4 cm. The spleen also acts as a reservoir for blood components. It can hold up to 240 ml of red blood cells, which can be released during cases of hypoxia or hypovolemia. It also stores platelets and up to a quarter of the body's lymphocytes.

Medical conditions can significantly affect the spleen. Splenomegaly is the term for an enlarged spleen. This can be caused by infections like mononucleosis, or diseases such as malaria, leukemia, and sickle cell anemia.

Severe trauma, such as a road traffic collision, can lead to splenic rupture, which is a medical emergency. If the spleen is surgically removed, the procedure is called a splenectomy. A person living without a spleen, a condition called asplenia, faces a higher risk of sepsis. This is specifically due to polysaccharide-encapsulated bacteria. Without the spleen's marginal zone to produce IgM memory B cells, the body struggles to clear these specific pathogens.

Understanding the spleen helps us understand the complex connections within the lymphatic and circulatory systems. The organ is connected to the central nervous system through the splenic plexus, which links the celiac ganglia to the vagus nerve. Its functions are also embedded into the hypothalamic–pituitary–adrenal axis. Some people are born with an accessory spleen, which is a small nodule of splenic tissue. This occurs in about 10 percent of the population. In some cases, called polysplenia, a person may have multiple small accessory spleens instead of one large organ. This condition is often linked to other developmental issues like cardiac abnormalities.