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Structure

Spleen

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The spleen is the largest lymphoid organ: a soft, highly vascular organ of the left upper abdomen that filters blood and initiates immune responses to blood-borne antigens. It is protected by the lower left ribs and is not normally palpable.

Terminologia Anatomica (Latin): Splen; Lien · Open in the 3D atlas

Location

Left hypochondrium, lying against the 9th to 11th ribs with its long axis along the 10th rib. It lies behind the stomach, in front of the left kidney, below the diaphragm and next to the splenic flexure; its hilum contacts the tail of the pancreas.

Structure

A capsule and trabeculae enclose the pulp. White pulp consists of periarteriolar lymphoid sheaths and follicles; red pulp consists of splenic cords and venous sinusoids; a marginal zone lies between them. The organ measures roughly 12 cm in length in adults, with considerable variation, and has a notched superior border.

Blood supply

The splenic artery, a branch of the coeliac trunk, runs along the upper border of the pancreas and divides into segmental branches at the hilum; short gastric and left gastroepiploic branches pass in the gastrosplenic ligament. The splenic vein joins the superior mesenteric vein behind the pancreatic neck to form the portal vein.

Innervation

Sympathetic fibres from the coeliac plexus accompany the splenic artery and are mainly vasomotor. There is no significant parasympathetic supply.

Function

The spleen removes senescent or abnormal red cells and particles, stores platelets, and mounts antibody responses, notably to encapsulated bacteria. It is also a site of fetal haematopoiesis and can resume blood formation in some diseases.

Clinical correlations

Splenomegaly occurs in portal hypertension, haematological disease and infection. The spleen is the most commonly injured solid organ in blunt abdominal trauma, often with left lower rib fractures. After splenectomy or functional asplenia there is a lifelong risk of overwhelming infection by encapsulated organisms; principles include vaccination and antibiotic prophylaxis according to local guidelines.

Common exam points

  • Lies under ribs 9 to 11 on the left; enlarges towards the right iliac fossa.
  • Supplied by the splenic artery (coeliac trunk); drained by the splenic vein into the portal system.
  • Palpable only when enlarged, roughly two to three times its normal size.
  • Rupture after trauma may cause haemorrhagic shock; left rib fractures raise suspicion.
  • Post-splenectomy: encapsulated organisms, vaccination, and Howell-Jolly bodies on the blood film.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Kumar V, Abbas AK, Aster JC. Robbins and Cotran Pathologic Basis of Disease. Elsevier, 10th edition (2020) — Tier 3 (textbook)

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