See it on the 3D body
The spleen lit on the 3D abdomen, as in the abdomen quiz. Turn the body, peel the layers, tap any structure for its name.
Quick answer
- Latin name
- Splen
- System
- Lymphatic and immune system
- Location
- Upper left abdomen, under the diaphragm and ribs 9 to 11, behind the stomach and against the upper part of the left kidney
- Function
- Filters the blood, removes old red blood cells, recycles iron and mounts immune responses against microbes in the blood
The spleen is a soft, dark red organ in the upper left abdomen, tucked under the lower ribs behind the stomach. It is the largest lymphatic organ of the body and works as a filter for the blood: it removes worn-out red blood cells and catches microbes, then helps the immune system respond to them.
Where it is
The spleen lies high in the left side of the abdomen, against the underside of the diaphragm. It sits behind and to the left of the stomach, against the upper part of the left kidney and above the left bend of the large intestine, and the ribs 9 to 11 cover it from the side.
A classic memory aid sums up its size and position with odd numbers: roughly 1 inch thick, 3 inches wide, 5 inches long, about 7 ounces, lying between ribs 9 and 11. These are rough averages for an adult, not exact values: the size and weight of the spleen vary a lot between people.
Its neighbors are on the liver and pancreas and stomach and intestines pages.
Structure
Shape and surfaces
The spleen has two surfaces:
- a smooth, curved diaphragmatic surface that faces up, out and back against the diaphragm;
- a hollow visceral surface that faces the other organs, with impressions for the stomach, the kidney and the colon.
Its upper border is often notched. In the middle of the visceral surface is the hilum, a slit where the vessels enter and leave. Folds of peritoneum, the gastrosplenic and splenorenal ligaments, tie it to the stomach and the left kidney.
Capsule and pulp
A thin capsule of connective tissue covers the spleen and sends partitions, called trabeculae, inside. The soft tissue between them is the pulp, of two kinds:
- The red pulp makes up most of the spleen. It is a sponge of blood-filled spaces, the sinusoids, and cords of tissue rich in macrophages, the cells that eat old red blood cells and debris.
- The white pulp forms small islands of lymphocytes around the arterioles. B cells gather in nodules and T cells around the vessels, much like in a lymph node.
- A marginal zone between the two traps particles from the blood and presents them to the lymphocytes.
Blood vessels
The splenic artery, a branch of the celiac trunk, runs along the upper border of the pancreas to the hilum. The splenic vein leaves the hilum, runs behind the pancreas and joins the superior mesenteric vein to form the hepatic portal vein. So blood from the spleen passes through the liver before it returns to the heart.
What it does
- Filters the blood. As blood seeps slowly through the red pulp, old or damaged red blood cells cannot squeeze back into the sinusoids. Macrophages engulf them.
- Recycles iron. The macrophages break down hemoglobin. Its iron is reused to make new red blood cells, and the rest becomes bilirubin, which the liver excretes in bile.
- Fights infection. The white pulp is where lymphocytes meet microbes carried in the blood and start an immune response, including making antibodies.
- Stores blood cells. It holds a reserve of platelets and monocytes.
- Makes blood cells before birth. In the fetus, the spleen and liver produce blood cells until the bone marrow takes over.
Unlike lymph nodes, the spleen filters blood, not lymph: no lymph vessels bring fluid into it.
How to study it
- Left, high and back. Picture the spleen tucked behind the stomach, under the left ribs, resting against the left kidney.
- Use the odd numbers. 1, 3, 5, 7, 9, 11: approximate thickness, width, length and weight, then the ribs that cover it.
- Red cleans, white defends. Red pulp filters the blood; white pulp holds the immune cells.
In Anatomy Atlas 3D, the spleen is part of the liver and pancreas set of the organ explorer, next to the tail of the pancreas. In the full body, turn the trunk to find it behind the stomach and tap it to see its English and Latin names. Hiding the stomach shows its visceral surface. Practice it in the abdomen quiz. The app is free on iPad and iPhone.
Frequently asked questions
Where is the spleen located?
In the upper left abdomen, under the diaphragm and ribs 9 to 11, behind the stomach and against the upper part of the left kidney.
What does the spleen do?
It filters the blood, removes old red blood cells, recycles their iron, stores platelets and helps the immune system fight microbes in the blood.
Can you live without a spleen?
Yes. Other organs, such as the liver and the lymph nodes, take over part of its work, although the risk of some infections is higher.
What is the difference between red pulp and white pulp?
Red pulp is filled with blood and macrophages and filters the blood. White pulp is made of lymphocytes and starts immune responses.
