Spleen

Q: What structures run within the gastrosplenic ligament?

The gastrosplenic ligament transmits: Short gastric arteries (aa. gastricae breves) — branches of the splenic artery heading toward the gastric fundus.Tail of the pancreas — approaches the splenic hilum within this ligament. Additionally, an accessory spleen (splen accessorius) may occasionally be located within the gastrosplenic ligament.

Q: Where does venous blood drain from the spleen?

Venous blood from the spleen drains into the splenic vein (v. splenica / v. lienalis), which is formed at the hilum by the confluence of multiple parenchymal veins. The splenic vein courses to the right and merges with the superior mesenteric vein to form the hepatic portal vein (v. portae hepatis). Inside the spleen, blood empties into splenic sinusoids (sinus splenicus), which mark the beginning of the venous system.

Q: Where can an accessory spleen be found?

An accessory spleen (splen accessorius) is most commonly located within the gastrosplenic ligament, close to the hilum of the main organ.

*splen*, *lien*

For medical students3 min readUpdated 2026-10-10

The spleen (splen, lien) is an unpaired parenchymatous organ of the lymphatic and circulatory systems, shaped roughly like a coffee bean. Located in the left hypochondrium between the diaphragm and the stomach, it performs critical immune and filtration functions.

SkeletotopyProjected between the left 9th and 11th ribs

FunctionKnown as the 'erythrocyte graveyard' — site of destruction for aging blood cells

StructureComposed of white pulp and red pulp

Blood SupplyBranches of the celiac trunk (*a. splenica*)

External Structure and Topography

The spleen is situated in the abdominal cavity. Its long axis runs almost parallel to the lower ribs. When projected onto the mid-axillary line, the organ lies strictly between the left 9th and 11th ribs.

The organ features two extremities:

Posterior end (extremitas posterior) — directed upward and backward toward the vertebral column, stopping about 4–5 cm short of it.
Anterior end (extremitas anterior) — directed downward and forward, reaching the left costal margin (projected along the anterior axillary line).

Shaped like a coffee bean, the spleen has two surfaces meeting at its borders. The diaphragmatic surface (facies diaphragmatica) is convex, smooth, and closely apposed to the diaphragm. The visceral surface (facies visceralis) is concave and faces the abdominal viscera.

These surfaces are separated by borders: the superior border (margo superior) is sharp, directed forward and upward, and typically features 2–3 characteristic notches; the inferior border (margo inferior) is blunt and faces backward and downward.

Hilum and Visceral Impressions

Occupying approximately the middle third of the visceral surface are the splenic hilum (hilum splenicum). This strategic depression is where nerves and arteries enter the parenchyma and veins exit. The hilum visually divides the visceral surface into lateral (superior) and medial halves.

Neighboring structures press closely against the spleen, leaving distinct impressions:

Gastric surface (facies gastrica) — located superior (lateral) to the hilum, contacting the posterior wall of the body, fundus, and greater curvature of the stomach.
Renal surface (facies renalis) — occupies the medial half, marking the contact zone with the left kidney and left suprarenal gland.
Colic surface (facies colica) — situated near the anterior end of the organ, where the left colic flexure approaches it.

The organ is almost entirely covered by visceral peritoneum (except at the hilum). Two important ligaments derived from the dorsal mesogastrium originate near the hilum:

Gastrosplenic ligament (lig. gastrosplenicum) — extends to the stomach. Its layers enclose the tail of the pancreas as it approaches the hilum, and occasionally harbor an accessory spleen (splen accessorius).
Splenorenal ligament (lig. splenorenale) — continues from the gastrosplenic ligament and anchors the organ to the left kidney.

Internal Structure: Capsule and Pulp

Externally, the spleen is covered by a serous coat (tunica serosa). Beneath it lies a dense fibrous capsule (tunica fibrosa), which sends connective tissue septa—trabeculae (trabeculae splenicae)—deep into the organ to form a robust internal framework.

All open spaces between the trabeculae are filled with functional tissue, the pulp, which is divided into two distinct types:

White pulp (pulpa alba) — consists of lymphatic follicles formed by lymphoid tissue.
Red pulp (pulpa rubra) — formed by reticular tissue whose meshes are packed with erythrocytes, macrophages, and leukocytes, along with a dense network of blood vessels.

Blood Supply, Innervation, and Functions

The primary blood supply comes from the splenic artery (a. splenica), a branch of the celiac trunk. A periarterial nerve plexus (plexus splenicus) accompanies the artery to provide autonomic innervation.

The intrasplenic vascular bed follows a unique hierarchy:

The artery branches into trabecular arteries (aa. trabeculares) running within the connective tissue septa.
These give off splenic branches (rr. splenici) to the lymphoid follicles.
Within the white pulp, vessels continue as central arteries (aa. centrales).
Inside the follicles, they branch into capillaries forming penicilli (penicilli).
Arteries empty into widened venous capillaries known as splenic sinusoids (sinus splenicus), initiating the venous drainage system.

Through this specialized architecture, the spleen performs several critical functions:

Participates in systemic immune responses.
Enriches the blood with newly developing leukocytes.
Executes phagocytosis: macrophages clear microorganisms and foreign particles.
Acts as an 'erythrocyte graveyard,' efficiently breaking down old and damaged red blood cells.

Mnemonic

To remember the skeletotopy of the spleen, use the numbers 9 and 11. The organ is projected onto the chest wall strictly between ribs IX and XI. You can associate this with the emergency number '911'—the spleen acts as a safety filter, actively destroying bacteria and worn-out red blood cells.

Frequently asked questions

Which ligaments anchor the spleen in the abdominal cavity?

The spleen is anchored by two peritoneal ligaments extending from its hilum:

Gastrosplenic ligament (lig. gastrosplenicum) — connects the spleen to the stomach.
Splenorenal ligament (lig. splenorenale) — connects the spleen to the left kidney (also referred to as the phrenicosplenic ligament).

The anterior end of the spleen rests on a peritoneal fold connecting the left colic flexure to the parietal peritoneum of the diaphragm—the phrenicocolic ligament.

What structures run within the gastrosplenic ligament?

The gastrosplenic ligament transmits:

Short gastric arteries (aa. gastricae breves) — branches of the splenic artery heading toward the gastric fundus.
Tail of the pancreas — approaches the splenic hilum within this ligament.

Additionally, an accessory spleen (splen accessorius) may occasionally be located within the gastrosplenic ligament.

Where does venous blood drain from the spleen?

Venous blood from the spleen drains into the splenic vein (v. splenica / v. lienalis), which is formed at the hilum by the confluence of multiple parenchymal veins. The splenic vein courses to the right and merges with the superior mesenteric vein to form the hepatic portal vein (v. portae hepatis). Inside the spleen, blood empties into splenic sinusoids (sinus splenicus), which mark the beginning of the venous system.

What structures form the white pulp of the spleen?

The white pulp of the spleen is formed by lymphoid tissue organized around arterial vessels into several distinct zones:

Periarterial lymphatic sheaths (PALS) — accumulations of T lymphocytes forming a 'sleeve' around pulpar arteries.
Lymphoid nodules (noduli lymphoidei splenici) — follicles with germinal centers surrounding central arteries, composed primarily of B cells.
Intermediate zone — area surrounding the sheath containing both T and B lymphocytes.
Marginal zone — located at the interface between the white and red pulp.

What structures pass through the hilum of the spleen?

The major blood vessels, lymphatic vessels, and nerves of the organ pass through the splenic hilum located on its visceral surface:

Splenic artery (a. splenica) — enters the hilum and divides into terminal segmental branches.
Splenic vein (v. splenica / v. lienalis) — exits the hilum, formed by parenchymal veins.
Lymphatic vessels — collect in the hilar region and exit the organ.
Nerves — enter the organ for autonomic innervation (periarterial plexus splenicus).

What is the difference between white and red pulp?

White pulp consists of lymphoid tissue and mediates immune responses. Red pulp is formed by reticular tissue whose spaces contain erythrocytes, leukocytes, and macrophages that filter the blood.

What structures pass through the splenic hilum?

Nerves enter, arteries pass through, and veins exit the organ via the hilum. The hilum itself lacks a peritoneal covering.

Where can an accessory spleen be found?

An accessory spleen (splen accessorius) is most commonly located within the gastrosplenic ligament, close to the hilum of the main organ.

Go deeper

Intrasplenic microcirculation: the pathway of blood from trabecular arteries to venous sinusoids
The ligamentous apparatus of the spleen as a derivative of the dorsal mesogastrium
Topography of the pancreatic tail relative to the splenic hilum
Visceral organ impressions: borders and anatomical relationships
Histological differentiation of white pulp lymphoid follicles