What is Spleen in Human Body Definition, Structure and Functions
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Harboured in the upper left abdomen, the spleen is the largest lymphoid tissue in the human body. The lymphatic or lymphoid organs are the major parts of the immune system, which acts as a shield or defences against diseases.
“The Facts on File Illustrated Guide to the Human Body” (2005) sheds some light on how the spleen filters out bacteria, debris, and old or damaged blood cells from the blood.
This article gives you useful and interesting information regarding “What is spleen in human body?” You’ll also learn about spleen definition, facts, and functions.
Here it is pertinent to talk about the immune system as the spleen has to play a role in immunity.The main function of the immune system is to protect you from the invasion of foreign organisms. It helps the body distinguish its tissues from external substances such as bacteria, viruses, and toxins.
Thus, dysfunction or deficiency of any component of the immune system can have serious repercussion for your health. For example, it can lead to various diseases ranging from arthritis toAIDS (Acquired Immunodeficiency Syndrome) and cancer.
Did you know? In the past, the spleen was perceived to be the seat of passions and emotions.The idiom ‘vent one’s spleen’ refers to the same concept.
Continue reading to discover more facts about spleen in human body.
The spleen can be defined as the largest gland of lymphatic system that is located to the left of the stomach and helps your body combat diseases and get rid of debris.
The Free Dictionaryputs the spleen definition as:
“The spleen is a large, highly vascular lymphoid organ located below the diaphragm and to the left of the stomach, which destroys old (or damaged) RBCs (Red Blood Cells), combats blood-borne antigens with its lymphocytes, and serves as a reservoir for blood.”
It means, in addition to being an important immune system organ, the spleen works in certain other capacities as well.
Location of the spleen
Spleen weighs about 150 gm in adults and lies under the diaphragm in the left upper part of the abdomen at the level between 9th and 11th ribs. Anterior to the spleen lies stomach and medially lies the superior part of the left kidney. Spleen resembles the size and shape of a clenched fist.
The organs of the body located near the spleen include gallbladder, pancreas, small intestine, and stomach. And the blood supply as viewed from below shows the structures like splenic veins, arteries, fibrous capsule, and the hilus.
Functions of the Spleen
- Primary Immune Response: Spleen participates in the primary immune response to invading bacteria, viruses, parasites, or foreign particles. In this way, the spleen is a strong defence against blood-borne pathogens. Removal of spleen increases the risk of infection.
- Blood Filter: Spleen acts like a filter for the blood; it removes cellular residues, particulate matter, senescent RBCs, and other abnormal cells from the bloodstream.
- Synthesis of Antibodies and Macrophages: Spleen synthesizes antibodies, macrophages, and lymphocytes in its white pulp. About 25% of the body's T lymphocytes and 15% of B lymphocytes are present in the spleen.
Removal of Old RBCs and Platelets: The red blood cells or erythrocytes in your body have an average life span of (100 to) 120 days after which they are destroyed mainly in the spleen. When the spleen is removed surgically due to any irreversible damage, increased numbers of abnormal RBCs are seen in blood smears.
In addition to disposing off old, aged, damaged red blood cells, the spleen also removes old defective platelets from the circulation.
- Blood Reservoir: The spleen can act like a blood reservoir. Owning to its spongy structure, the spleen can enlarge and store up to 1000 ml of blood. Similarly, when needed, it can also help stabilize the blood volume by transferring excess plasma from the bloodstream into the lymphatic system.
- Production of Blood Cells: In certain diseases such as leukaemia or extreme anaemia, the spleen can resume its role of producing blood cells; this function is usually present during foetal life.
- Synthesis of Opsonins: The spleen is also involved in the synthesis of the proteins like tuftsin and properdin. These proteins act as opsoninsin countering an infection or a disease. An opsoninmay be an antibody or some other particle,which binds with foreign microorganisms or cells to make it easy for the phagocytes to engulf them.
Disorders of the Spleen
It is the abnormal enlargement of spleen. When the spleen is diseased, it can be 10 times larger than its normal size.
The causes of splenomegaly include:
- Parasitic infection such as malaria, and kala azar (black fever or Dumdum fever)
- Chronic tuberculosis
- Typhoid, septic shock, and infective endocarditis
- Rheumatoid arthritis and systemic lupus erythematosus
- Portal hypertension and liver diseases
- Lymphomas, anaemia, and leukaemia
It is the surgical removal of spleen and is usually performed due to severe trauma or rupture of the spleen. In the long run there is an increased risk of overwhelming infections after the splenectomy of the spleen. Numbers of platelets in the blood are also increased immediately.
- Rachael Grace in “Fast Facts for Patients and Supporters: Pyruvate Kinase Deficiency” reveals an interesting fact about your spleen that its removal can improve anaemia for most people with pyruvate kinase deficiency.
- The red pulp of the spleen, acting as a filter, is engaged in the removal of old/aged red blood cells and other matter.
- Did you know your spleen receives about five percent of the total cardiac output every minute?
- 90% of the blood entering the spleen is emptied into the open circulation of the “red pulp”.
- The white pulp of the spleen is involved in the immunological function. And it can be divided into two zones –the B lymphocyte zone and the T lymphocyte zone.