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Overview of Spleen Anatomy and Physiology

The spleen is a vital organ located in the upper left quadrant of the abdomen, playing crucial roles in immune response, blood filtration, and red blood cell recycling.

Anatomy of the Spleen

• Location:
  • Situated in the upper left quadrant of the abdomen, beneath the diaphragm and next to the stomach.
• Structure:
  • Capsule: A fibrous capsule surrounds the spleen.
  • Red Pulp: Contains sinusoids filled with blood and splenic cords; involved in filtering blood and recycling old red blood cells.
  • White Pulp: Contains lymphoid tissue; involved in immune response.
  • Hilum: The site where blood vessels and nerves enter and exit the spleen.

Physiology of the Spleen

• Blood Filtration:
  • Filters and removes old or damaged red blood cells and platelets from the blood.
  • Macrophages in the red pulp phagocytize these cells and recycle their components, such as iron.
• Immune Function:
  • White pulp contains lymphocytes (B and T cells) that initiate immune responses against blood-borne pathogens.
  • Produces antibodies and activates macrophages to engulf pathogens.
  • Acts as a reservoir for monocytes, which can be mobilized to sites of infection or injury.
• Blood Reservoir:
  • Stores blood and can release it during instances of haemorrhage or hypovolemic shock to maintain blood volume and pressure.
• Hematopoiesis:
  • In fetuses, the spleen is involved in the production of red and white blood cells.
  • In adults, it can revert to hematopoiesis under certain pathological conditions (extramedullary hematopoiesis).

Clinical Relevance

• Splenomegaly:
  • Enlargement of the spleen due to various conditions such as infections (e.g., mononucleosis), liver diseases (e.g., cirrhosis), and hematologic disorders (e.g., leukaemia, lymphoma).
  • Symptoms: Pain or fullness in the left upper abdomen, fatigue, frequent infections, and easy bleeding.
• Asplenia:
  • Absence of spleen function, which can be congenital or acquired (e.g., surgical removal).
  • Increases susceptibility to infections, particularly from encapsulated bacteria (e.g., Streptococcus pneumoniae, Haemophilus influenzae).
  • Prophylactic measures: Vaccinations and prophylactic antibiotics.
• Spleen Rupture:
  • Occurs due to trauma or pathological enlargement.
  • Can lead to life-threatening internal bleeding.
  • Symptoms: Severe pain in the left upper abdomen, tenderness, and signs of hypovolemic shock (e.g., low blood pressure, rapid heart rate).
  • Treatment: Emergency surgery (splenectomy) to remove the spleen and control bleeding.
• Hypersplenism:
  • Overactive spleen that removes blood cells too quickly, leading to cytopenias (e.g., anaemia, leukopenia, thrombocytopenia).
  • Associated with conditions such as liver disease, infections, and autoimmune disorders.
  • Treatment may involve addressing the underlying condition or splenectomy.

Summary

The spleen is a vital organ involved in blood filtration, immune response, and red blood cell recycling. Understanding its anatomy and physiology is essential for diagnosing and managing conditions affecting the spleen, such as splenomegaly, asplenia, spleen rupture, and hypersplenism.