Spleen – Location, Function, Problems


The Spleen

The spleen is a vital organ in the lymphatic system, playing crucial roles in immunological defense and blood filtration. Here is a look at the spleen, its location, anatomical features, functions, and clinical significance.

  • The spleen is in the upper left abdomen, under the diaphragm, and next to the stomach.
  • It functions in blood filtration, removing old red blood cells, and recycling iron.
  • The spleen plays a critical role in the immune system, housing white blood cells that produce antibodies.
  • It acts as a reservoir for blood, platelets, and monocytes, releasing them during hemorrhage or infection.
  • Splenectomy or removal of the spleen is survivable, but it increases susceptibility to infections.

Where Is the Spleen Located?

In humans, the spleen is in the upper left quadrant of the abdomen, beneath the diaphragm and adjacent to the stomach. It is a fist-sized organ. In adult humans, a typical spleen is around 12 cm in length, 7 cm in width, and 4 cm in thickness, weighing approximately 150-200 grams. The size depends on height, weight, and the level of congestion, but not age or sex. The spleen has a soft, spongy texture and a purplish hue due to its rich blood supply.

Proximity to Other Organs

The spleen rests between the stomach and the left kidney, with its convex surface facing the diaphragm and its concave surface in contact with the stomach, pancreas, and left kidney. This proximity to major organs underscores its role in systemic physiology and pathology.

Spleen Anatomy

Human Spleen Anatomy and Histology

A dense connective tissue capsule covers the spleen. Trabeculae extend inward, dividing the organ into lobules. Internally, the spleen consists of two main regions:

  1. Red Pulp: This area filters blood, removing old or damaged red blood cells, and storing platelets and monocytes.
  2. White Pulp: This lymphoid tissue plays an important role in the immune response, containing lymphocytes and macrophages that identify and attack pathogens.

Comparative Anatomy

The spleen is present in vertebrates, including mammals, birds, fish, amphibians, and reptiles. In fact, the only vertebrates lacking a spleen are hagfish and lampreys (both jawless fish). However, the structure and function of the organ varies. For example, in some fish and amphibians, the spleen is less developed. It is Y-shaped in marsupials. Invertebrates do not have a spleen.

Functions of the Spleen

The spleen performs multiple critical functions:

  1. Hematopoiesis: The spleen produces blood cells in a fetus. While it stops producing red blood cells after the 5th month of gestation, it continues making lymphocytes (a type of white blood cell).
  2. Blood Filtration: The spleen filters blood, removing aged or damaged red blood cells and recycling iron.
  3. Immune Response: The spleen detects and responds to pathogens, producing antibodies and activating lymphocytes.
  4. Reservoir Function: The spleen stores blood, platelets, and monocytes, releasing them during hemorrhage or infection.
  5. Phagocytosis: Macrophages in the spleen engulf and destroy pathogens and cellular debris.

Embryonic Development

The spleen is unusual compared with other abdominal organs in that it derives from mesenchymal tissue (the dorsal mesentery). In contrast, most gut organs derive from the endoderm. Even so, the spleen shares the blood supply (the celiac trunk) with these other organs.

Possible Problems With the Spleen

Ruptured Spleen

A ruptured spleen is a medical emergency often resulting from trauma, such as a car accident or sports injury. The spleen’s delicate tissue can tear, leading to internal bleeding. Symptoms include abdominal pain, tenderness, and signs of hypovolemic shock (e.g., low blood pressure, rapid heart rate). A ruptured spleen is potentially fatal due to significant blood loss, so it requires immediate surgical intervention.

Enlarged Spleen (Splenomegaly)

Splenomegaly refers to an enlarged spleen. This results from a variety of causes, including:

  • Infections: Viral (e.g., mononucleosis), bacterial (e.g., tuberculosis), parasitic (e.g., malaria).
  • Liver Diseases: Cirrhosis leading to portal hypertension.
  • Hematologic Disorders: Leukemia, lymphoma, hemolytic anemia.
  • Inflammatory Diseases: Rheumatoid arthritis, systemic lupus erythematosus.
  • Metabolic Disorders: Gaucher disease, Niemann-Pick disease.

Symptoms of splenomegaly include pain or fullness in the left upper abdomen, fatigue, and increased susceptibility to infections. Treatment depends on the underlying cause and involves addressing the primary condition or, in severe cases, removal of the spleen or splenectomy.

Can You Live Without a Spleen?

A person can live without a spleen, but its absence compromises the immune system. Splenectomy (surgical removal of the spleen) is sometimes necessary due to trauma, disease, or cancer. Post-splenectomy, individuals are more susceptible to infections, particularly from encapsulated bacteria like Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Prophylactic antibiotics and vaccinations aid in managing this increased risk. One study indicates the risk of cancer does not increase following splenectomy.

Maintaining a Healthy Spleen

Tips for maintaining a healthy spleen include:

  • Regular Check-ups: Routine medical examinations detect any abnormalities early.
  • Vaccinations: Keeping up with vaccinations reduces the risk of infections that can damage the spleen.
  • Healthy Lifestyle: A healthy lifestyle includes a balanced diet, regular exercise, and avoiding excessive alcohol consumption.
  • Injury Prevention: Take precautions to avoid abdominal trauma, such as wearing seat belts and protective gear during sports.

References

  • Bynum, B. (2002). “The spleen”. Lancet. 359 (9317): 1624. doi:10.1016/S0140-6736(02)08479-9
  • Lori, Andrea; Perrotta, Marialuisa; Lembo, Giuseppe; Carnevale, Daniela (2017). “The Spleen: A Hub Connecting Nervous and Immune Systems in Cardiovascular and Metabolic Diseases”. International Journal of Molecular Sciences. 18 (6): 1216. doi:10.3390/ijms18061216
  • Mebius, RE; Kraal, G (2005). “Structure and function of the spleen”. Nature Reviews Immunology. 5 (8): 606–16. doi:10.1038/nri1669
  • Robinette, C. D.; Fraumeni, J. F. (1977). “Splenectomy and Subsequent Mortality in Veterans of the 1939–45 War”. The Lancet. 310 (8029): 127–29. doi:10.1016/S0140-6736(77)90132-5
  • Swirski, F.K.; Nahrendorf, M.; et al. (2009). “Identification of splenic reservoir monocytes and their deployment to inflammatory sites”. Science. 325 (5940): 612–16. doi:10.1126/science.1175202